doc

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doc

原文：https://pkg.go.dev/cmd/doc@go1.19.3

Overview

Doc (usually run as go doc) accepts zero, one or two arguments.

doc（通常作为 go doc 运行）接受零个、一个或两个参数。

Zero arguments:

零个参数：

go doc

Show the documentation for the package in the current directory.

显示当前目录中包的文档。一个参数：

One argument:

此列表中第一个成功的项是打印其文档的项。如果存在符号但没有包，则选择当前目录中的包。但是，如果参数以大写字母开头，则始终假定它是当前目录中的符号。两个参数：

go doc <pkg>
go doc <sym>[.<methodOrField>]
go doc [<pkg>.]<sym>[.<methodOrField>]
go doc [<pkg>.][<sym>.]<methodOrField>

The first item in this list that succeeds is the one whose documentation is printed. If there is a symbol but no package, the package in the current directory is chosen. However, if the argument begins with a capital letter it is always assumed to be a symbol in the current directory.

显示包、符号以及方法或字段的文档。第一个参数必须是完整的包路径。这类似于 godoc 命令的命令行用法。

Two arguments:

对于命令，除非存在 -cmd 标志，否则“go doc command”仅显示包的包级文档。

go doc <pkg> <sym>[.<methodOrField>]

Show the documentation for the package, symbol, and method or field. The first argument must be a full package path. This is similar to the command-line usage for the godoc command.

-src 标志导致 doc 打印符号的完整源代码，例如结构、函数或方法的主体。

For commands, unless the -cmd flag is present “go doc command” shows only the package-level docs for the package.

-all 标志导致 doc 打印包及其所有可见符号的所有文档。参数必须标识一个包。

The -src flag causes doc to print the full source code for the symbol, such as the body of a struct, function or method.

有关完整文档，请运行“go help doc”。

The -all flag causes doc to print all documentation for the package and all its visible symbols. The argument must identify a package.

For complete documentation, run “go help doc”.

=== “dirs.go”

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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"sync"

	"golang.org/x/mod/semver"
)

// A Dir describes a directory holding code by specifying
// the expected import path and the file system directory.
type Dir struct {
	importPath string // import path for that dir
	dir        string // file system directory
	inModule   bool
}

// Dirs is a structure for scanning the directory tree.
// Its Next method returns the next Go source directory it finds.
// Although it can be used to scan the tree multiple times, it
// only walks the tree once, caching the data it finds.
type Dirs struct {
	scan   chan Dir // Directories generated by walk.
	hist   []Dir    // History of reported Dirs.
	offset int      // Counter for Next.
}

var dirs Dirs

// dirsInit starts the scanning of package directories in GOROOT and GOPATH. Any
// extra paths passed to it are included in the channel.
func dirsInit(extra ...Dir) {
	if buildCtx.GOROOT == "" {
		stdout, err := exec.Command("go", "env", "GOROOT").Output()
		if err != nil {
			if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
				log.Fatalf("failed to determine GOROOT: $GOROOT is not set and 'go env GOROOT' failed:\n%s", ee.Stderr)
			}
			log.Fatalf("failed to determine GOROOT: $GOROOT is not set and could not run 'go env GOROOT':\n\t%s", err)
		}
		buildCtx.GOROOT = string(bytes.TrimSpace(stdout))
	}

	dirs.hist = make([]Dir, 0, 1000)
	dirs.hist = append(dirs.hist, extra...)
	dirs.scan = make(chan Dir)
	go dirs.walk(codeRoots())
}

// goCmd returns the "go" command path corresponding to buildCtx.GOROOT.
func goCmd() string {
	if buildCtx.GOROOT == "" {
		return "go"
	}
	return filepath.Join(buildCtx.GOROOT, "bin", "go")
}

// Reset puts the scan back at the beginning.
func (d *Dirs) Reset() {
	d.offset = 0
}

// Next returns the next directory in the scan. The boolean
// is false when the scan is done.
func (d *Dirs) Next() (Dir, bool) {
	if d.offset < len(d.hist) {
		dir := d.hist[d.offset]
		d.offset++
		return dir, true
	}
	dir, ok := <-d.scan
	if !ok {
		return Dir{}, false
	}
	d.hist = append(d.hist, dir)
	d.offset++
	return dir, ok
}

// walk walks the trees in GOROOT and GOPATH.
func (d *Dirs) walk(roots []Dir) {
	for _, root := range roots {
		d.bfsWalkRoot(root)
	}
	close(d.scan)
}

// bfsWalkRoot walks a single directory hierarchy in breadth-first lexical order.
// Each Go source directory it finds is delivered on d.scan.
func (d *Dirs) bfsWalkRoot(root Dir) {
	root.dir = filepath.Clean(root.dir) // because filepath.Join will do it anyway

	// this is the queue of directories to examine in this pass.
	this := []string{}
	// next is the queue of directories to examine in the next pass.
	next := []string{root.dir}

	for len(next) > 0 {
		this, next = next, this[0:0]
		for _, dir := range this {
			fd, err := os.Open(dir)
			if err != nil {
				log.Print(err)
				continue
			}
			entries, err := fd.Readdir(0)
			fd.Close()
			if err != nil {
				log.Print(err)
				continue
			}
			hasGoFiles := false
			for _, entry := range entries {
				name := entry.Name()
				// For plain files, remember if this directory contains any .go
				// source files, but ignore them otherwise.
				if !entry.IsDir() {
					if !hasGoFiles && strings.HasSuffix(name, ".go") {
						hasGoFiles = true
					}
					continue
				}
				// Entry is a directory.

				// The go tool ignores directories starting with ., _, or named "testdata".
				if name[0] == '.' || name[0] == '_' || name == "testdata" {
					continue
				}
				// When in a module, ignore vendor directories and stop at module boundaries.
				if root.inModule {
					if name == "vendor" {
						continue
					}
					if fi, err := os.Stat(filepath.Join(dir, name, "go.mod")); err == nil && !fi.IsDir() {
						continue
					}
				}
				// Remember this (fully qualified) directory for the next pass.
				next = append(next, filepath.Join(dir, name))
			}
			if hasGoFiles {
				// It's a candidate.
				importPath := root.importPath
				if len(dir) > len(root.dir) {
					if importPath != "" {
						importPath += "/"
					}
					importPath += filepath.ToSlash(dir[len(root.dir)+1:])
				}
				d.scan <- Dir{importPath, dir, root.inModule}
			}
		}

	}
}

var testGOPATH = false // force GOPATH use for testing

// codeRoots returns the code roots to search for packages.
// In GOPATH mode this is GOROOT/src and GOPATH/src, with empty import paths.
// In module mode, this is each module root, with an import path set to its module path.
func codeRoots() []Dir {
	codeRootsCache.once.Do(func() {
		codeRootsCache.roots = findCodeRoots()
	})
	return codeRootsCache.roots
}

var codeRootsCache struct {
	once  sync.Once
	roots []Dir
}

var usingModules bool

func findCodeRoots() []Dir {
	var list []Dir
	if !testGOPATH {
		// Check for use of modules by 'go env GOMOD',
		// which reports a go.mod file path if modules are enabled.
		stdout, _ := exec.Command(goCmd(), "env", "GOMOD").Output()
		gomod := string(bytes.TrimSpace(stdout))

		usingModules = len(gomod) > 0
		if usingModules && buildCtx.GOROOT != "" {
			list = append(list,
				Dir{dir: filepath.Join(buildCtx.GOROOT, "src"), inModule: true},
				Dir{importPath: "cmd", dir: filepath.Join(buildCtx.GOROOT, "src", "cmd"), inModule: true})
		}

		if gomod == os.DevNull {
			// Modules are enabled, but the working directory is outside any module.
			// We can still access std, cmd, and packages specified as source files
			// on the command line, but there are no module roots.
			// Avoid 'go list -m all' below, since it will not work.
			return list
		}
	}

	if !usingModules {
		if buildCtx.GOROOT != "" {
			list = append(list, Dir{dir: filepath.Join(buildCtx.GOROOT, "src")})
		}
		for _, root := range splitGopath() {
			list = append(list, Dir{dir: filepath.Join(root, "src")})
		}
		return list
	}

	// Find module root directories from go list.
	// Eventually we want golang.org/x/tools/go/packages
	// to handle the entire file system search and become go/packages,
	// but for now enumerating the module roots lets us fit modules
	// into the current code with as few changes as possible.
	mainMod, vendorEnabled, err := vendorEnabled()
	if err != nil {
		return list
	}
	if vendorEnabled {
		// Add the vendor directory to the search path ahead of "std".
		// That way, if the main module *is* "std", we will identify the path
		// without the "vendor/" prefix before the one with that prefix.
		list = append([]Dir{{dir: filepath.Join(mainMod.Dir, "vendor"), inModule: false}}, list...)
		if mainMod.Path != "std" {
			list = append(list, Dir{importPath: mainMod.Path, dir: mainMod.Dir, inModule: true})
		}
		return list
	}

	cmd := exec.Command(goCmd(), "list", "-m", "-f={{.Path}}\t{{.Dir}}", "all")
	cmd.Stderr = os.Stderr
	out, _ := cmd.Output()
	for _, line := range strings.Split(string(out), "\n") {
		path, dir, _ := strings.Cut(line, "\t")
		if dir != "" {
			list = append(list, Dir{importPath: path, dir: dir, inModule: true})
		}
	}

	return list
}

// The functions below are derived from x/tools/internal/imports at CL 203017.

type moduleJSON struct {
	Path, Dir, GoVersion string
}

var modFlagRegexp = regexp.MustCompile(`-mod[ =](\w+)`)

// vendorEnabled indicates if vendoring is enabled.
// Inspired by setDefaultBuildMod in modload/init.go
func vendorEnabled() (*moduleJSON, bool, error) {
	mainMod, go114, err := getMainModuleAnd114()
	if err != nil {
		return nil, false, err
	}

	stdout, _ := exec.Command(goCmd(), "env", "GOFLAGS").Output()
	goflags := string(bytes.TrimSpace(stdout))
	matches := modFlagRegexp.FindStringSubmatch(goflags)
	var modFlag string
	if len(matches) != 0 {
		modFlag = matches[1]
	}
	if modFlag != "" {
		// Don't override an explicit '-mod=' argument.
		return mainMod, modFlag == "vendor", nil
	}
	if mainMod == nil || !go114 {
		return mainMod, false, nil
	}
	// Check 1.14's automatic vendor mode.
	if fi, err := os.Stat(filepath.Join(mainMod.Dir, "vendor")); err == nil && fi.IsDir() {
		if mainMod.GoVersion != "" && semver.Compare("v"+mainMod.GoVersion, "v1.14") >= 0 {
			// The Go version is at least 1.14, and a vendor directory exists.
			// Set -mod=vendor by default.
			return mainMod, true, nil
		}
	}
	return mainMod, false, nil
}

// getMainModuleAnd114 gets the main module's information and whether the
// go command in use is 1.14+. This is the information needed to figure out
// if vendoring should be enabled.
func getMainModuleAnd114() (*moduleJSON, bool, error) {
	const format = `{{.Path}}
{{.Dir}}
{{.GoVersion}}
{{range context.ReleaseTags}}{{if eq . "go1.14"}}{{.}}{{end}}{{end}}
`
	cmd := exec.Command(goCmd(), "list", "-m", "-f", format)
	cmd.Stderr = os.Stderr
	stdout, err := cmd.Output()
	if err != nil {
		return nil, false, nil
	}
	lines := strings.Split(string(stdout), "\n")
	if len(lines) < 5 {
		return nil, false, fmt.Errorf("unexpected stdout: %q", stdout)
	}
	mod := &moduleJSON{
		Path:      lines[0],
		Dir:       lines[1],
		GoVersion: lines[2],
	}
	return mod, lines[3] == "go1.14", nil
}

=== “doc_test.go”

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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"flag"
	"go/build"
	"internal/testenv"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	"testing"
)

func TestMain(m *testing.M) {
	// Clear GOPATH so we don't access the user's own packages in the test.
	buildCtx.GOPATH = ""
	testGOPATH = true // force GOPATH mode; module test is in cmd/go/testdata/script/mod_doc.txt

	// Set GOROOT in case runtime.GOROOT is wrong (for example, if the test was
	// built with -trimpath). dirsInit would identify it using 'go env GOROOT',
	// but we can't be sure that the 'go' in $PATH is the right one either.
	buildCtx.GOROOT = testenv.GOROOT(nil)
	build.Default.GOROOT = testenv.GOROOT(nil)

	// Add $GOROOT/src/cmd/doc/testdata explicitly so we can access its contents in the test.
	// Normally testdata directories are ignored, but sending it to dirs.scan directly is
	// a hack that works around the check.
	testdataDir, err := filepath.Abs("testdata")
	if err != nil {
		panic(err)
	}
	dirsInit(
		Dir{importPath: "testdata", dir: testdataDir},
		Dir{importPath: "testdata/nested", dir: filepath.Join(testdataDir, "nested")},
		Dir{importPath: "testdata/nested/nested", dir: filepath.Join(testdataDir, "nested", "nested")})

	os.Exit(m.Run())
}

func maybeSkip(t *testing.T) {
	if runtime.GOOS == "ios" {
		t.Skip("iOS does not have a full file tree")
	}
}

type isDotSlashTest struct {
	str    string
	result bool
}

var isDotSlashTests = []isDotSlashTest{
	{``, false},
	{`x`, false},
	{`...`, false},
	{`.../`, false},
	{`...\`, false},

	{`.`, true},
	{`./`, true},
	{`.\`, true},
	{`./x`, true},
	{`.\x`, true},

	{`..`, true},
	{`../`, true},
	{`..\`, true},
	{`../x`, true},
	{`..\x`, true},
}

func TestIsDotSlashPath(t *testing.T) {
	for _, test := range isDotSlashTests {
		if result := isDotSlash(test.str); result != test.result {
			t.Errorf("isDotSlash(%q) = %t; expected %t", test.str, result, test.result)
		}
	}
}

type test struct {
	name string
	args []string // Arguments to "[go] doc".
	yes  []string // Regular expressions that should match.
	no   []string // Regular expressions that should not match.
}

const p = "cmd/doc/testdata"

var tests = []test{
	// Sanity check.
	{
		"sanity check",
		[]string{p},
		[]string{`type ExportedType struct`},
		nil,
	},

	// Package dump includes import, package statement.
	{
		"package clause",
		[]string{p},
		[]string{`package pkg.*cmd/doc/testdata`},
		nil,
	},

	// Constants.
	// Package dump
	{
		"full package",
		[]string{p},
		[]string{
			`Package comment`,
			`const ExportedConstant = 1`,                                   // Simple constant.
			`const ConstOne = 1`,                                           // First entry in constant block.
			`const ConstFive ...`,                                          // From block starting with unexported constant.
			`var ExportedVariable = 1`,                                     // Simple variable.
			`var VarOne = 1`,                                               // First entry in variable block.
			`func ExportedFunc\(a int\) bool`,                              // Function.
			`func ReturnUnexported\(\) unexportedType`,                     // Function with unexported return type.
			`type ExportedType struct{ ... }`,                              // Exported type.
			`const ExportedTypedConstant ExportedType = iota`,              // Typed constant.
			`const ExportedTypedConstant_unexported unexportedType`,        // Typed constant, exported for unexported type.
			`const ConstLeft2 uint64 ...`,                                  // Typed constant using unexported iota.
			`const ConstGroup1 unexportedType = iota ...`,                  // Typed constant using unexported type.
			`const ConstGroup4 ExportedType = ExportedType{}`,              // Typed constant using exported type.
			`const MultiLineConst = ...`,                                   // Multi line constant.
			`var MultiLineVar = map\[struct{ ... }\]struct{ ... }{ ... }`,  // Multi line variable.
			`func MultiLineFunc\(x interface{ ... }\) \(r struct{ ... }\)`, // Multi line function.
			`var LongLine = newLongLine\(("someArgument[1-4]", ){4}...\)`,  // Long list of arguments.
			`type T1 = T2`,                                                 // Type alias
			`type SimpleConstraint interface{ ... }`,
			`type TildeConstraint interface{ ... }`,
			`type StructConstraint interface{ ... }`,
		},
		[]string{
			`const internalConstant = 2`,       // No internal constants.
			`var internalVariable = 2`,         // No internal variables.
			`func internalFunc(a int) bool`,    // No internal functions.
			`Comment about exported constant`,  // No comment for single constant.
			`Comment about exported variable`,  // No comment for single variable.
			`Comment about block of constants`, // No comment for constant block.
			`Comment about block of variables`, // No comment for variable block.
			`Comment before ConstOne`,          // No comment for first entry in constant block.
			`Comment before VarOne`,            // No comment for first entry in variable block.
			`ConstTwo = 2`,                     // No second entry in constant block.
			`VarTwo = 2`,                       // No second entry in variable block.
			`VarFive = 5`,                      // From block starting with unexported variable.
			`type unexportedType`,              // No unexported type.
			`unexportedTypedConstant`,          // No unexported typed constant.
			`\bField`,                          // No fields.
			`Method`,                           // No methods.
			`someArgument[5-8]`,                // No truncated arguments.
			`type T1 T2`,                       // Type alias does not display as type declaration.
		},
	},
	// Package dump -all
	{
		"full package",
		[]string{"-all", p},
		[]string{
			`package pkg .*import`,
			`Package comment`,
			`CONSTANTS`,
			`Comment before ConstOne`,
			`ConstOne = 1`,
			`ConstTwo = 2 // Comment on line with ConstTwo`,
			`ConstFive`,
			`ConstSix`,
			`Const block where first entry is unexported`,
			`ConstLeft2, constRight2 uint64`,
			`constLeft3, ConstRight3`,
			`ConstLeft4, ConstRight4`,
			`Duplicate = iota`,
			`const CaseMatch = 1`,
			`const Casematch = 2`,
			`const ExportedConstant = 1`,
			`const MultiLineConst = `,
			`MultiLineString1`,
			`VARIABLES`,
			`Comment before VarOne`,
			`VarOne = 1`,
			`Comment about block of variables`,
			`VarFive = 5`,
			`var ExportedVariable = 1`,
			`var ExportedVarOfUnExported unexportedType`,
			`var LongLine = newLongLine\(`,
			`var MultiLineVar = map\[struct {`,
			`FUNCTIONS`,
			`func ExportedFunc\(a int\) bool`,
			`Comment about exported function`,
			`func MultiLineFunc\(x interface`,
			`func ReturnUnexported\(\) unexportedType`,
			`TYPES`,
			`type ExportedInterface interface`,
			`type ExportedStructOneField struct`,
			`type ExportedType struct`,
			`Comment about exported type`,
			`const ConstGroup4 ExportedType = ExportedType`,
			`ExportedTypedConstant ExportedType = iota`,
			`Constants tied to ExportedType`,
			`func ExportedTypeConstructor\(\) \*ExportedType`,
			`Comment about constructor for exported type`,
			`func ReturnExported\(\) ExportedType`,
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`Comment about exported method`,
			`type T1 = T2`,
			`type T2 int`,
			`type SimpleConstraint interface {`,
			`type TildeConstraint interface {`,
			`type StructConstraint interface {`,
		},
		[]string{
			`constThree`,
			`_, _ uint64 = 2 \* iota, 1 << iota`,
			`constLeft1, constRight1`,
			`duplicate`,
			`varFour`,
			`func internalFunc`,
			`unexportedField`,
			`func \(unexportedType\)`,
		},
	},
	// Package with just the package declaration. Issue 31457.
	{
		"only package declaration",
		[]string{"-all", p + "/nested/empty"},
		[]string{`package empty .*import`},
		nil,
	},
	// Package dump -short
	{
		"full package with -short",
		[]string{`-short`, p},
		[]string{
			`const ExportedConstant = 1`,               // Simple constant.
			`func ReturnUnexported\(\) unexportedType`, // Function with unexported return type.
		},
		[]string{
			`MultiLine(String|Method|Field)`, // No data from multi line portions.
		},
	},
	// Package dump -u
	{
		"full package with u",
		[]string{`-u`, p},
		[]string{
			`const ExportedConstant = 1`,               // Simple constant.
			`const internalConstant = 2`,               // Internal constants.
			`func internalFunc\(a int\) bool`,          // Internal functions.
			`func ReturnUnexported\(\) unexportedType`, // Function with unexported return type.
		},
		[]string{
			`Comment about exported constant`,  // No comment for simple constant.
			`Comment about block of constants`, // No comment for constant block.
			`Comment about internal function`,  // No comment for internal function.
			`MultiLine(String|Method|Field)`,   // No data from multi line portions.
		},
	},
	// Package dump -u -all
	{
		"full package",
		[]string{"-u", "-all", p},
		[]string{
			`package pkg .*import`,
			`Package comment`,
			`CONSTANTS`,
			`Comment before ConstOne`,
			`ConstOne += 1`,
			`ConstTwo += 2 // Comment on line with ConstTwo`,
			`constThree = 3 // Comment on line with constThree`,
			`ConstFive`,
			`const internalConstant += 2`,
			`Comment about internal constant`,
			`VARIABLES`,
			`Comment before VarOne`,
			`VarOne += 1`,
			`Comment about block of variables`,
			`varFour += 4`,
			`VarFive += 5`,
			`varSix += 6`,
			`var ExportedVariable = 1`,
			`var LongLine = newLongLine\(`,
			`var MultiLineVar = map\[struct {`,
			`var internalVariable = 2`,
			`Comment about internal variable`,
			`FUNCTIONS`,
			`func ExportedFunc\(a int\) bool`,
			`Comment about exported function`,
			`func MultiLineFunc\(x interface`,
			`func internalFunc\(a int\) bool`,
			`Comment about internal function`,
			`func newLongLine\(ss .*string\)`,
			`TYPES`,
			`type ExportedType struct`,
			`type T1 = T2`,
			`type T2 int`,
			`type unexportedType int`,
			`Comment about unexported type`,
			`ConstGroup1 unexportedType = iota`,
			`ConstGroup2`,
			`ConstGroup3`,
			`ExportedTypedConstant_unexported unexportedType = iota`,
			`Constants tied to unexportedType`,
			`const unexportedTypedConstant unexportedType = 1`,
			`func ReturnUnexported\(\) unexportedType`,
			`func \(unexportedType\) ExportedMethod\(\) bool`,
			`func \(unexportedType\) unexportedMethod\(\) bool`,
		},
		nil,
	},

	// Single constant.
	{
		"single constant",
		[]string{p, `ExportedConstant`},
		[]string{
			`Comment about exported constant`, // Include comment.
			`const ExportedConstant = 1`,
		},
		nil,
	},
	// Single constant -u.
	{
		"single constant with -u",
		[]string{`-u`, p, `internalConstant`},
		[]string{
			`Comment about internal constant`, // Include comment.
			`const internalConstant = 2`,
		},
		nil,
	},
	// Block of constants.
	{
		"block of constants",
		[]string{p, `ConstTwo`},
		[]string{
			`Comment before ConstOne.\n.*ConstOne = 1`,    // First...
			`ConstTwo = 2.*Comment on line with ConstTwo`, // And second show up.
			`Comment about block of constants`,            // Comment does too.
		},
		[]string{
			`constThree`, // No unexported constant.
		},
	},
	// Block of constants -u.
	{
		"block of constants with -u",
		[]string{"-u", p, `constThree`},
		[]string{
			`constThree = 3.*Comment on line with constThree`,
		},
		nil,
	},
	// Block of constants -src.
	{
		"block of constants with -src",
		[]string{"-src", p, `ConstTwo`},
		[]string{
			`Comment about block of constants`, // Top comment.
			`ConstOne.*=.*1`,                   // Each constant seen.
			`ConstTwo.*=.*2.*Comment on line with ConstTwo`,
			`constThree`, // Even unexported constants.
		},
		nil,
	},
	// Block of constants with carryover type from unexported field.
	{
		"block of constants with carryover type",
		[]string{p, `ConstLeft2`},
		[]string{
			`ConstLeft2, constRight2 uint64`,
			`constLeft3, ConstRight3`,
			`ConstLeft4, ConstRight4`,
		},
		nil,
	},
	// Block of constants -u with carryover type from unexported field.
	{
		"block of constants with carryover type",
		[]string{"-u", p, `ConstLeft2`},
		[]string{
			`_, _ uint64 = 2 \* iota, 1 << iota`,
			`constLeft1, constRight1`,
			`ConstLeft2, constRight2`,
			`constLeft3, ConstRight3`,
			`ConstLeft4, ConstRight4`,
		},
		nil,
	},

	// Single variable.
	{
		"single variable",
		[]string{p, `ExportedVariable`},
		[]string{
			`ExportedVariable`, // Include comment.
			`var ExportedVariable = 1`,
		},
		nil,
	},
	// Single variable -u.
	{
		"single variable with -u",
		[]string{`-u`, p, `internalVariable`},
		[]string{
			`Comment about internal variable`, // Include comment.
			`var internalVariable = 2`,
		},
		nil,
	},
	// Block of variables.
	{
		"block of variables",
		[]string{p, `VarTwo`},
		[]string{
			`Comment before VarOne.\n.*VarOne = 1`,    // First...
			`VarTwo = 2.*Comment on line with VarTwo`, // And second show up.
			`Comment about block of variables`,        // Comment does too.
		},
		[]string{
			`varThree= 3`, // No unexported variable.
		},
	},
	// Block of variables -u.
	{
		"block of variables with -u",
		[]string{"-u", p, `varThree`},
		[]string{
			`varThree = 3.*Comment on line with varThree`,
		},
		nil,
	},

	// Function.
	{
		"function",
		[]string{p, `ExportedFunc`},
		[]string{
			`Comment about exported function`, // Include comment.
			`func ExportedFunc\(a int\) bool`,
		},
		nil,
	},
	// Function -u.
	{
		"function with -u",
		[]string{"-u", p, `internalFunc`},
		[]string{
			`Comment about internal function`, // Include comment.
			`func internalFunc\(a int\) bool`,
		},
		nil,
	},
	// Function with -src.
	{
		"function with -src",
		[]string{"-src", p, `ExportedFunc`},
		[]string{
			`Comment about exported function`, // Include comment.
			`func ExportedFunc\(a int\) bool`,
			`return true != false`, // Include body.
		},
		nil,
	},

	// Type.
	{
		"type",
		[]string{p, `ExportedType`},
		[]string{
			`Comment about exported type`, // Include comment.
			`type ExportedType struct`,    // Type definition.
			`Comment before exported field.*\n.*ExportedField +int` +
				`.*Comment on line with exported field`,
			`ExportedEmbeddedType.*Comment on line with exported embedded field`,
			`Has unexported fields`,
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`const ExportedTypedConstant ExportedType = iota`, // Must include associated constant.
			`func ExportedTypeConstructor\(\) \*ExportedType`, // Must include constructor.
			`io.Reader.*Comment on line with embedded Reader`,
		},
		[]string{
			`unexportedField`,               // No unexported field.
			`int.*embedded`,                 // No unexported embedded field.
			`Comment about exported method`, // No comment about exported method.
			`unexportedMethod`,              // No unexported method.
			`unexportedTypedConstant`,       // No unexported constant.
			`error`,                         // No embedded error.
		},
	},
	// Type with -src. Will see unexported fields.
	{
		"type",
		[]string{"-src", p, `ExportedType`},
		[]string{
			`Comment about exported type`, // Include comment.
			`type ExportedType struct`,    // Type definition.
			`Comment before exported field`,
			`ExportedField.*Comment on line with exported field`,
			`ExportedEmbeddedType.*Comment on line with exported embedded field`,
			`unexportedType.*Comment on line with unexported embedded field`,
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`const ExportedTypedConstant ExportedType = iota`, // Must include associated constant.
			`func ExportedTypeConstructor\(\) \*ExportedType`, // Must include constructor.
			`io.Reader.*Comment on line with embedded Reader`,
		},
		[]string{
			`Comment about exported method`, // No comment about exported method.
			`unexportedMethod`,              // No unexported method.
			`unexportedTypedConstant`,       // No unexported constant.
		},
	},
	// Type -all.
	{
		"type",
		[]string{"-all", p, `ExportedType`},
		[]string{
			`type ExportedType struct {`,                        // Type definition as source.
			`Comment about exported type`,                       // Include comment afterwards.
			`const ConstGroup4 ExportedType = ExportedType\{\}`, // Related constants.
			`ExportedTypedConstant ExportedType = iota`,
			`Constants tied to ExportedType`,
			`func ExportedTypeConstructor\(\) \*ExportedType`,
			`Comment about constructor for exported type.`,
			`func ReturnExported\(\) ExportedType`,
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`Comment about exported method.`,
			`func \(ExportedType\) Uncommented\(a int\) bool\n\n`, // Ensure line gap after method with no comment
		},
		[]string{
			`unexportedType`,
		},
	},
	// Type T1 dump (alias).
	{
		"type T1",
		[]string{p + ".T1"},
		[]string{
			`type T1 = T2`,
		},
		[]string{
			`type T1 T2`,
			`type ExportedType`,
		},
	},
	// Type -u with unexported fields.
	{
		"type with unexported fields and -u",
		[]string{"-u", p, `ExportedType`},
		[]string{
			`Comment about exported type`, // Include comment.
			`type ExportedType struct`,    // Type definition.
			`Comment before exported field.*\n.*ExportedField +int`,
			`unexportedField.*int.*Comment on line with unexported field`,
			`ExportedEmbeddedType.*Comment on line with exported embedded field`,
			`\*ExportedEmbeddedType.*Comment on line with exported embedded \*field`,
			`\*qualified.ExportedEmbeddedType.*Comment on line with exported embedded \*selector.field`,
			`unexportedType.*Comment on line with unexported embedded field`,
			`\*unexportedType.*Comment on line with unexported embedded \*field`,
			`io.Reader.*Comment on line with embedded Reader`,
			`error.*Comment on line with embedded error`,
			`func \(ExportedType\) unexportedMethod\(a int\) bool`,
			`unexportedTypedConstant`,
		},
		[]string{
			`Has unexported fields`,
		},
	},
	// Unexported type with -u.
	{
		"unexported type with -u",
		[]string{"-u", p, `unexportedType`},
		[]string{
			`Comment about unexported type`, // Include comment.
			`type unexportedType int`,       // Type definition.
			`func \(unexportedType\) ExportedMethod\(\) bool`,
			`func \(unexportedType\) unexportedMethod\(\) bool`,
			`ExportedTypedConstant_unexported unexportedType = iota`,
			`const unexportedTypedConstant unexportedType = 1`,
		},
		nil,
	},

	// Interface.
	{
		"interface type",
		[]string{p, `ExportedInterface`},
		[]string{
			`Comment about exported interface`, // Include comment.
			`type ExportedInterface interface`, // Interface definition.
			`Comment before exported method.\n.*//\n.*//	// Code block showing how to use ExportedMethod\n.*//	func DoSomething\(\) error {\n.*//		ExportedMethod\(\)\n.*//		return nil\n.*//	}\n.*//.*\n.*ExportedMethod\(\)` +
				`.*Comment on line with exported method`,
			`io.Reader.*Comment on line with embedded Reader`,
			`error.*Comment on line with embedded error`,
			`Has unexported methods`,
		},
		[]string{
			`unexportedField`,               // No unexported field.
			`Comment about exported method`, // No comment about exported method.
			`unexportedMethod`,              // No unexported method.
			`unexportedTypedConstant`,       // No unexported constant.
		},
	},
	// Interface -u with unexported methods.
	{
		"interface type with unexported methods and -u",
		[]string{"-u", p, `ExportedInterface`},
		[]string{
			`Comment about exported interface`, // Include comment.
			`type ExportedInterface interface`, // Interface definition.
			`Comment before exported method.\n.*//\n.*//	// Code block showing how to use ExportedMethod\n.*//	func DoSomething\(\) error {\n.*//		ExportedMethod\(\)\n.*//		return nil\n.*//	}\n.*//.*\n.*ExportedMethod\(\)` + `.*Comment on line with exported method`,
			`unexportedMethod\(\).*Comment on line with unexported method`,
			`io.Reader.*Comment on line with embedded Reader`,
			`error.*Comment on line with embedded error`,
		},
		[]string{
			`Has unexported methods`,
		},
	},

	// Interface method.
	{
		"interface method",
		[]string{p, `ExportedInterface.ExportedMethod`},
		[]string{
			`Comment before exported method.\n.*//\n.*//	// Code block showing how to use ExportedMethod\n.*//	func DoSomething\(\) error {\n.*//		ExportedMethod\(\)\n.*//		return nil\n.*//	}\n.*//.*\n.*ExportedMethod\(\)` +
				`.*Comment on line with exported method`,
		},
		[]string{
			`Comment about exported interface`,
		},
	},
	// Interface method at package level.
	{
		"interface method at package level",
		[]string{p, `ExportedMethod`},
		[]string{
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`Comment about exported method`,
		},
		[]string{
			`Comment before exported method.*\n.*ExportedMethod\(\)` +
				`.*Comment on line with exported method`,
		},
	},

	// Method.
	{
		"method",
		[]string{p, `ExportedType.ExportedMethod`},
		[]string{
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`Comment about exported method`,
		},
		nil,
	},
	// Method  with -u.
	{
		"method with -u",
		[]string{"-u", p, `ExportedType.unexportedMethod`},
		[]string{
			`func \(ExportedType\) unexportedMethod\(a int\) bool`,
			`Comment about unexported method`,
		},
		nil,
	},
	// Method with -src.
	{
		"method with -src",
		[]string{"-src", p, `ExportedType.ExportedMethod`},
		[]string{
			`func \(ExportedType\) ExportedMethod\(a int\) bool`,
			`Comment about exported method`,
			`return true != true`,
		},
		nil,
	},

	// Field.
	{
		"field",
		[]string{p, `ExportedType.ExportedField`},
		[]string{
			`type ExportedType struct`,
			`ExportedField int`,
			`Comment before exported field`,
			`Comment on line with exported field`,
			`other fields elided`,
		},
		nil,
	},

	// Field with -u.
	{
		"method with -u",
		[]string{"-u", p, `ExportedType.unexportedField`},
		[]string{
			`unexportedField int`,
			`Comment on line with unexported field`,
		},
		nil,
	},

	// Field of struct with only one field.
	{
		"single-field struct",
		[]string{p, `ExportedStructOneField.OnlyField`},
		[]string{`the only field`},
		[]string{`other fields elided`},
	},

	// Case matching off.
	{
		"case matching off",
		[]string{p, `casematch`},
		[]string{
			`CaseMatch`,
			`Casematch`,
		},
		nil,
	},

	// Case matching on.
	{
		"case matching on",
		[]string{"-c", p, `Casematch`},
		[]string{
			`Casematch`,
		},
		[]string{
			`CaseMatch`,
		},
	},

	// Merging comments with -src.
	{
		"merge comments with -src A",
		[]string{"-src", p + "/merge", `A`},
		[]string{
			`A doc`,
			`func A`,
			`A comment`,
		},
		[]string{
			`Package A doc`,
			`Package B doc`,
			`B doc`,
			`B comment`,
			`B doc`,
		},
	},
	{
		"merge comments with -src B",
		[]string{"-src", p + "/merge", `B`},
		[]string{
			`B doc`,
			`func B`,
			`B comment`,
		},
		[]string{
			`Package A doc`,
			`Package B doc`,
			`A doc`,
			`A comment`,
			`A doc`,
		},
	},

	// No dups with -u. Issue 21797.
	{
		"case matching on, no dups",
		[]string{"-u", p, `duplicate`},
		[]string{
			`Duplicate`,
			`duplicate`,
		},
		[]string{
			"\\)\n+const", // This will appear if the const decl appears twice.
		},
	},
	{
		"non-imported: pkg.sym",
		[]string{"nested.Foo"},
		[]string{"Foo struct"},
		nil,
	},
	{
		"non-imported: pkg only",
		[]string{"nested"},
		[]string{"Foo struct"},
		nil,
	},
	{
		"non-imported: pkg sym",
		[]string{"nested", "Foo"},
		[]string{"Foo struct"},
		nil,
	},
	{
		"formatted doc on function",
		[]string{p, "ExportedFormattedDoc"},
		[]string{
			`func ExportedFormattedDoc\(a int\) bool`,
			`    Comment about exported function with formatting\.

    Example

        fmt\.Println\(FormattedDoc\(\)\)

    Text after pre-formatted block\.`,
		},
		nil,
	},
	{
		"formatted doc on type field",
		[]string{p, "ExportedFormattedType.ExportedField"},
		[]string{
			`type ExportedFormattedType struct`,
			`    // Comment before exported field with formatting\.
    //[ ]
    // Example
    //[ ]
    //     a\.ExportedField = 123
    //[ ]
    // Text after pre-formatted block\.`,
			`ExportedField int`,
		},
		nil,
	},
}

func TestDoc(t *testing.T) {
	maybeSkip(t)
	defer log.SetOutput(log.Writer())
	for _, test := range tests {
		var b bytes.Buffer
		var flagSet flag.FlagSet
		var logbuf bytes.Buffer
		log.SetOutput(&logbuf)
		err := do(&b, &flagSet, test.args)
		if err != nil {
			t.Fatalf("%s %v: %s\n", test.name, test.args, err)
		}
		if logbuf.Len() > 0 {
			t.Errorf("%s %v: unexpected log messages:\n%s", test.name, test.args, logbuf.Bytes())
		}
		output := b.Bytes()
		failed := false
		for j, yes := range test.yes {
			re, err := regexp.Compile(yes)
			if err != nil {
				t.Fatalf("%s.%d: compiling %#q: %s", test.name, j, yes, err)
			}
			if !re.Match(output) {
				t.Errorf("%s.%d: no match for %s %#q", test.name, j, test.args, yes)
				failed = true
			}
		}
		for j, no := range test.no {
			re, err := regexp.Compile(no)
			if err != nil {
				t.Fatalf("%s.%d: compiling %#q: %s", test.name, j, no, err)
			}
			if re.Match(output) {
				t.Errorf("%s.%d: incorrect match for %s %#q", test.name, j, test.args, no)
				failed = true
			}
		}
		if bytes.Count(output, []byte("TYPES\n")) > 1 {
			t.Fatalf("%s: repeating headers", test.name)
		}
		if failed {
			t.Logf("\n%s", output)
		}
	}
}

// Test the code to try multiple packages. Our test case is
//
//	go doc rand.Float64
//
// This needs to find math/rand.Float64; however crypto/rand, which doesn't
// have the symbol, usually appears first in the directory listing.
func TestMultiplePackages(t *testing.T) {
	if testing.Short() {
		t.Skip("scanning file system takes too long")
	}
	maybeSkip(t)
	var b bytes.Buffer // We don't care about the output.
	// Make sure crypto/rand does not have the symbol.
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"crypto/rand.float64"})
		if err == nil {
			t.Errorf("expected error from crypto/rand.float64")
		} else if !strings.Contains(err.Error(), "no symbol float64") {
			t.Errorf("unexpected error %q from crypto/rand.float64", err)
		}
	}
	// Make sure math/rand does have the symbol.
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"math/rand.float64"})
		if err != nil {
			t.Errorf("unexpected error %q from math/rand.float64", err)
		}
	}
	// Try the shorthand.
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"rand.float64"})
		if err != nil {
			t.Errorf("unexpected error %q from rand.float64", err)
		}
	}
	// Now try a missing symbol. We should see both packages in the error.
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"rand.doesnotexit"})
		if err == nil {
			t.Errorf("expected error from rand.doesnotexit")
		} else {
			errStr := err.Error()
			if !strings.Contains(errStr, "no symbol") {
				t.Errorf("error %q should contain 'no symbol", errStr)
			}
			if !strings.Contains(errStr, "crypto/rand") {
				t.Errorf("error %q should contain crypto/rand", errStr)
			}
			if !strings.Contains(errStr, "math/rand") {
				t.Errorf("error %q should contain math/rand", errStr)
			}
		}
	}
}

// Test the code to look up packages when given two args. First test case is
//
//	go doc binary BigEndian
//
// This needs to find encoding/binary.BigEndian, which means
// finding the package encoding/binary given only "binary".
// Second case is
//
//	go doc rand Float64
//
// which again needs to find math/rand and not give up after crypto/rand,
// which has no such function.
func TestTwoArgLookup(t *testing.T) {
	if testing.Short() {
		t.Skip("scanning file system takes too long")
	}
	maybeSkip(t)
	var b bytes.Buffer // We don't care about the output.
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"binary", "BigEndian"})
		if err != nil {
			t.Errorf("unexpected error %q from binary BigEndian", err)
		}
	}
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"rand", "Float64"})
		if err != nil {
			t.Errorf("unexpected error %q from rand Float64", err)
		}
	}
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"bytes", "Foo"})
		if err == nil {
			t.Errorf("expected error from bytes Foo")
		} else if !strings.Contains(err.Error(), "no symbol Foo") {
			t.Errorf("unexpected error %q from bytes Foo", err)
		}
	}
	{
		var flagSet flag.FlagSet
		err := do(&b, &flagSet, []string{"nosuchpackage", "Foo"})
		if err == nil {
			// actually present in the user's filesystem
		} else if !strings.Contains(err.Error(), "no such package") {
			t.Errorf("unexpected error %q from nosuchpackage Foo", err)
		}
	}
}

// Test the code to look up packages when the first argument starts with "./".
// Our test case is in effect "cd src/text; doc ./template". This should get
// text/template but before Issue 23383 was fixed would give html/template.
func TestDotSlashLookup(t *testing.T) {
	if testing.Short() {
		t.Skip("scanning file system takes too long")
	}
	maybeSkip(t)
	where, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}
	defer func() {
		if err := os.Chdir(where); err != nil {
			t.Fatal(err)
		}
	}()
	if err := os.Chdir(filepath.Join(buildCtx.GOROOT, "src", "text")); err != nil {
		t.Fatal(err)
	}
	var b bytes.Buffer
	var flagSet flag.FlagSet
	err = do(&b, &flagSet, []string{"./template"})
	if err != nil {
		t.Errorf("unexpected error %q from ./template", err)
	}
	// The output should contain information about the text/template package.
	const want = `package template // import "text/template"`
	output := b.String()
	if !strings.HasPrefix(output, want) {
		t.Fatalf("wrong package: %.*q...", len(want), output)
	}
}

// Test that we don't print spurious package clauses
// when there should be no output at all. Issue 37969.
func TestNoPackageClauseWhenNoMatch(t *testing.T) {
	maybeSkip(t)
	var b bytes.Buffer
	var flagSet flag.FlagSet
	err := do(&b, &flagSet, []string{"template.ZZZ"})
	// Expect an error.
	if err == nil {
		t.Error("expect an error for template.zzz")
	}
	// And the output should not contain any package clauses.
	const dontWant = `package template // import `
	output := b.String()
	if strings.Contains(output, dontWant) {
		t.Fatalf("improper package clause printed:\n%s", output)
	}
}

type trimTest struct {
	path   string
	prefix string
	result string
	ok     bool
}

var trimTests = []trimTest{
	{"", "", "", true},
	{"/usr/gopher", "/usr/gopher", "/usr/gopher", true},
	{"/usr/gopher/bar", "/usr/gopher", "bar", true},
	{"/usr/gopherflakes", "/usr/gopher", "/usr/gopherflakes", false},
	{"/usr/gopher/bar", "/usr/zot", "/usr/gopher/bar", false},
}

func TestTrim(t *testing.T) {
	for _, test := range trimTests {
		result, ok := trim(test.path, test.prefix)
		if ok != test.ok {
			t.Errorf("%s %s expected %t got %t", test.path, test.prefix, test.ok, ok)
			continue
		}
		if result != test.result {
			t.Errorf("%s %s expected %q got %q", test.path, test.prefix, test.result, result)
			continue
		}
	}
}

=== “main.go”

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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Doc (usually run as go doc) accepts zero, one or two arguments.
//
// Zero arguments:
//
//	go doc
//
// Show the documentation for the package in the current directory.
//
// One argument:
//
//	go doc <pkg>
//	go doc <sym>[.<methodOrField>]
//	go doc [<pkg>.]<sym>[.<methodOrField>]
//	go doc [<pkg>.][<sym>.]<methodOrField>
//
// The first item in this list that succeeds is the one whose documentation
// is printed. If there is a symbol but no package, the package in the current
// directory is chosen. However, if the argument begins with a capital
// letter it is always assumed to be a symbol in the current directory.
//
// Two arguments:
//
//	go doc <pkg> <sym>[.<methodOrField>]
//
// Show the documentation for the package, symbol, and method or field. The
// first argument must be a full package path. This is similar to the
// command-line usage for the godoc command.
//
// For commands, unless the -cmd flag is present "go doc command"
// shows only the package-level docs for the package.
//
// The -src flag causes doc to print the full source code for the symbol, such
// as the body of a struct, function or method.
//
// The -all flag causes doc to print all documentation for the package and
// all its visible symbols. The argument must identify a package.
//
// For complete documentation, run "go help doc".
package main

import (
	"bytes"
	"flag"
	"fmt"
	"go/build"
	"go/token"
	"io"
	"log"
	"os"
	"path"
	"path/filepath"
	"strings"
)

var (
	unexported bool // -u flag
	matchCase  bool // -c flag
	showAll    bool // -all flag
	showCmd    bool // -cmd flag
	showSrc    bool // -src flag
	short      bool // -short flag
)

// usage is a replacement usage function for the flags package.
func usage() {
	fmt.Fprintf(os.Stderr, "Usage of [go] doc:\n")
	fmt.Fprintf(os.Stderr, "\tgo doc\n")
	fmt.Fprintf(os.Stderr, "\tgo doc <pkg>\n")
	fmt.Fprintf(os.Stderr, "\tgo doc <sym>[.<methodOrField>]\n")
	fmt.Fprintf(os.Stderr, "\tgo doc [<pkg>.]<sym>[.<methodOrField>]\n")
	fmt.Fprintf(os.Stderr, "\tgo doc [<pkg>.][<sym>.]<methodOrField>\n")
	fmt.Fprintf(os.Stderr, "\tgo doc <pkg> <sym>[.<methodOrField>]\n")
	fmt.Fprintf(os.Stderr, "For more information run\n")
	fmt.Fprintf(os.Stderr, "\tgo help doc\n\n")
	fmt.Fprintf(os.Stderr, "Flags:\n")
	flag.PrintDefaults()
	os.Exit(2)
}

func main() {
	log.SetFlags(0)
	log.SetPrefix("doc: ")
	dirsInit()
	err := do(os.Stdout, flag.CommandLine, os.Args[1:])
	if err != nil {
		log.Fatal(err)
	}
}

// do is the workhorse, broken out of main to make testing easier.
func do(writer io.Writer, flagSet *flag.FlagSet, args []string) (err error) {
	flagSet.Usage = usage
	unexported = false
	matchCase = false
	flagSet.BoolVar(&unexported, "u", false, "show unexported symbols as well as exported")
	flagSet.BoolVar(&matchCase, "c", false, "symbol matching honors case (paths not affected)")
	flagSet.BoolVar(&showAll, "all", false, "show all documentation for package")
	flagSet.BoolVar(&showCmd, "cmd", false, "show symbols with package docs even if package is a command")
	flagSet.BoolVar(&showSrc, "src", false, "show source code for symbol")
	flagSet.BoolVar(&short, "short", false, "one-line representation for each symbol")
	flagSet.Parse(args)
	var paths []string
	var symbol, method string
	// Loop until something is printed.
	dirs.Reset()
	for i := 0; ; i++ {
		buildPackage, userPath, sym, more := parseArgs(flagSet.Args())
		if i > 0 && !more { // Ignore the "more" bit on the first iteration.
			return failMessage(paths, symbol, method)
		}
		if buildPackage == nil {
			return fmt.Errorf("no such package: %s", userPath)
		}

		// The builtin package needs special treatment: its symbols are lower
		// case but we want to see them, always.
		if buildPackage.ImportPath == "builtin" {
			unexported = true
		}

		symbol, method = parseSymbol(sym)
		pkg := parsePackage(writer, buildPackage, userPath)
		paths = append(paths, pkg.prettyPath())

		defer func() {
			pkg.flush()
			e := recover()
			if e == nil {
				return
			}
			pkgError, ok := e.(PackageError)
			if ok {
				err = pkgError
				return
			}
			panic(e)
		}()

		// We have a package.
		if showAll && symbol == "" {
			pkg.allDoc()
			return
		}

		switch {
		case symbol == "":
			pkg.packageDoc() // The package exists, so we got some output.
			return
		case method == "":
			if pkg.symbolDoc(symbol) {
				return
			}
		default:
			if pkg.methodDoc(symbol, method) {
				return
			}
			if pkg.fieldDoc(symbol, method) {
				return
			}
		}
	}
}

// failMessage creates a nicely formatted error message when there is no result to show.
func failMessage(paths []string, symbol, method string) error {
	var b bytes.Buffer
	if len(paths) > 1 {
		b.WriteString("s")
	}
	b.WriteString(" ")
	for i, path := range paths {
		if i > 0 {
			b.WriteString(", ")
		}
		b.WriteString(path)
	}
	if method == "" {
		return fmt.Errorf("no symbol %s in package%s", symbol, &b)
	}
	return fmt.Errorf("no method or field %s.%s in package%s", symbol, method, &b)
}

// parseArgs analyzes the arguments (if any) and returns the package
// it represents, the part of the argument the user used to identify
// the path (or "" if it's the current package) and the symbol
// (possibly with a .method) within that package.
// parseSymbol is used to analyze the symbol itself.
// The boolean final argument reports whether it is possible that
// there may be more directories worth looking at. It will only
// be true if the package path is a partial match for some directory
// and there may be more matches. For example, if the argument
// is rand.Float64, we must scan both crypto/rand and math/rand
// to find the symbol, and the first call will return crypto/rand, true.
func parseArgs(args []string) (pkg *build.Package, path, symbol string, more bool) {
	wd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	if len(args) == 0 {
		// Easy: current directory.
		return importDir(wd), "", "", false
	}
	arg := args[0]
	// We have an argument. If it is a directory name beginning with . or ..,
	// use the absolute path name. This discriminates "./errors" from "errors"
	// if the current directory contains a non-standard errors package.
	if isDotSlash(arg) {
		arg = filepath.Join(wd, arg)
	}
	switch len(args) {
	default:
		usage()
	case 1:
		// Done below.
	case 2:
		// Package must be findable and importable.
		pkg, err := build.Import(args[0], wd, build.ImportComment)
		if err == nil {
			return pkg, args[0], args[1], false
		}
		for {
			packagePath, ok := findNextPackage(arg)
			if !ok {
				break
			}
			if pkg, err := build.ImportDir(packagePath, build.ImportComment); err == nil {
				return pkg, arg, args[1], true
			}
		}
		return nil, args[0], args[1], false
	}
	// Usual case: one argument.
	// If it contains slashes, it begins with either a package path
	// or an absolute directory.
	// First, is it a complete package path as it is? If so, we are done.
	// This avoids confusion over package paths that have other
	// package paths as their prefix.
	var importErr error
	if filepath.IsAbs(arg) {
		pkg, importErr = build.ImportDir(arg, build.ImportComment)
		if importErr == nil {
			return pkg, arg, "", false
		}
	} else {
		pkg, importErr = build.Import(arg, wd, build.ImportComment)
		if importErr == nil {
			return pkg, arg, "", false
		}
	}
	// Another disambiguator: If the argument starts with an upper
	// case letter, it can only be a symbol in the current directory.
	// Kills the problem caused by case-insensitive file systems
	// matching an upper case name as a package name.
	if !strings.ContainsAny(arg, `/\`) && token.IsExported(arg) {
		pkg, err := build.ImportDir(".", build.ImportComment)
		if err == nil {
			return pkg, "", arg, false
		}
	}
	// If it has a slash, it must be a package path but there is a symbol.
	// It's the last package path we care about.
	slash := strings.LastIndex(arg, "/")
	// There may be periods in the package path before or after the slash
	// and between a symbol and method.
	// Split the string at various periods to see what we find.
	// In general there may be ambiguities but this should almost always
	// work.
	var period int
	// slash+1: if there's no slash, the value is -1 and start is 0; otherwise
	// start is the byte after the slash.
	for start := slash + 1; start < len(arg); start = period + 1 {
		period = strings.Index(arg[start:], ".")
		symbol := ""
		if period < 0 {
			period = len(arg)
		} else {
			period += start
			symbol = arg[period+1:]
		}
		// Have we identified a package already?
		pkg, err := build.Import(arg[0:period], wd, build.ImportComment)
		if err == nil {
			return pkg, arg[0:period], symbol, false
		}
		// See if we have the basename or tail of a package, as in json for encoding/json
		// or ivy/value for robpike.io/ivy/value.
		pkgName := arg[:period]
		for {
			path, ok := findNextPackage(pkgName)
			if !ok {
				break
			}
			if pkg, err = build.ImportDir(path, build.ImportComment); err == nil {
				return pkg, arg[0:period], symbol, true
			}
		}
		dirs.Reset() // Next iteration of for loop must scan all the directories again.
	}
	// If it has a slash, we've failed.
	if slash >= 0 {
		// build.Import should always include the path in its error message,
		// and we should avoid repeating it. Unfortunately, build.Import doesn't
		// return a structured error. That can't easily be fixed, since it
		// invokes 'go list' and returns the error text from the loaded package.
		// TODO(golang.org/issue/34750): load using golang.org/x/tools/go/packages
		// instead of go/build.
		importErrStr := importErr.Error()
		if strings.Contains(importErrStr, arg[:period]) {
			log.Fatal(importErrStr)
		} else {
			log.Fatalf("no such package %s: %s", arg[:period], importErrStr)
		}
	}
	// Guess it's a symbol in the current directory.
	return importDir(wd), "", arg, false
}

// dotPaths lists all the dotted paths legal on Unix-like and
// Windows-like file systems. We check them all, as the chance
// of error is minute and even on Windows people will use ./
// sometimes.
var dotPaths = []string{
	`./`,
	`../`,
	`.\`,
	`..\`,
}

// isDotSlash reports whether the path begins with a reference
// to the local . or .. directory.
func isDotSlash(arg string) bool {
	if arg == "." || arg == ".." {
		return true
	}
	for _, dotPath := range dotPaths {
		if strings.HasPrefix(arg, dotPath) {
			return true
		}
	}
	return false
}

// importDir is just an error-catching wrapper for build.ImportDir.
func importDir(dir string) *build.Package {
	pkg, err := build.ImportDir(dir, build.ImportComment)
	if err != nil {
		log.Fatal(err)
	}
	return pkg
}

// parseSymbol breaks str apart into a symbol and method.
// Both may be missing or the method may be missing.
// If present, each must be a valid Go identifier.
func parseSymbol(str string) (symbol, method string) {
	if str == "" {
		return
	}
	elem := strings.Split(str, ".")
	switch len(elem) {
	case 1:
	case 2:
		method = elem[1]
	default:
		log.Printf("too many periods in symbol specification")
		usage()
	}
	symbol = elem[0]
	return
}

// isExported reports whether the name is an exported identifier.
// If the unexported flag (-u) is true, isExported returns true because
// it means that we treat the name as if it is exported.
func isExported(name string) bool {
	return unexported || token.IsExported(name)
}

// findNextPackage returns the next full file name path that matches the
// (perhaps partial) package path pkg. The boolean reports if any match was found.
func findNextPackage(pkg string) (string, bool) {
	if filepath.IsAbs(pkg) {
		if dirs.offset == 0 {
			dirs.offset = -1
			return pkg, true
		}
		return "", false
	}
	if pkg == "" || token.IsExported(pkg) { // Upper case symbol cannot be a package name.
		return "", false
	}
	pkg = path.Clean(pkg)
	pkgSuffix := "/" + pkg
	for {
		d, ok := dirs.Next()
		if !ok {
			return "", false
		}
		if d.importPath == pkg || strings.HasSuffix(d.importPath, pkgSuffix) {
			return d.dir, true
		}
	}
}

var buildCtx = build.Default

// splitGopath splits $GOPATH into a list of roots.
func splitGopath() []string {
	return filepath.SplitList(buildCtx.GOPATH)
}

=== “pkg.go”

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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bufio"
	"bytes"
	"fmt"
	"go/ast"
	"go/build"
	"go/doc"
	"go/format"
	"go/parser"
	"go/printer"
	"go/token"
	"io"
	"io/fs"
	"log"
	"path/filepath"
	"strings"
	"unicode"
	"unicode/utf8"
)

const (
	punchedCardWidth = 80
	indent           = "    "
)

type Package struct {
	writer      io.Writer    // Destination for output.
	name        string       // Package name, json for encoding/json.
	userPath    string       // String the user used to find this package.
	pkg         *ast.Package // Parsed package.
	file        *ast.File    // Merged from all files in the package
	doc         *doc.Package
	build       *build.Package
	typedValue  map[*doc.Value]bool // Consts and vars related to types.
	constructor map[*doc.Func]bool  // Constructors.
	fs          *token.FileSet      // Needed for printing.
	buf         pkgBuffer
}

func (p *Package) ToText(w io.Writer, text, prefix, codePrefix string) {
	d := p.doc.Parser().Parse(text)
	pr := p.doc.Printer()
	pr.TextPrefix = prefix
	pr.TextCodePrefix = codePrefix
	w.Write(pr.Text(d))
}

// pkgBuffer is a wrapper for bytes.Buffer that prints a package clause the
// first time Write is called.
type pkgBuffer struct {
	pkg     *Package
	printed bool // Prevent repeated package clauses.
	bytes.Buffer
}

func (pb *pkgBuffer) Write(p []byte) (int, error) {
	pb.packageClause()
	return pb.Buffer.Write(p)
}

func (pb *pkgBuffer) packageClause() {
	if !pb.printed {
		pb.printed = true
		// Only show package clause for commands if requested explicitly.
		if pb.pkg.pkg.Name != "main" || showCmd {
			pb.pkg.packageClause()
		}
	}
}

type PackageError string // type returned by pkg.Fatalf.

func (p PackageError) Error() string {
	return string(p)
}

// prettyPath returns a version of the package path that is suitable for an
// error message. It obeys the import comment if present. Also, since
// pkg.build.ImportPath is sometimes the unhelpful "" or ".", it looks for a
// directory name in GOROOT or GOPATH if that happens.
func (pkg *Package) prettyPath() string {
	path := pkg.build.ImportComment
	if path == "" {
		path = pkg.build.ImportPath
	}
	if path != "." && path != "" {
		return path
	}
	// Convert the source directory into a more useful path.
	// Also convert everything to slash-separated paths for uniform handling.
	path = filepath.Clean(filepath.ToSlash(pkg.build.Dir))
	// Can we find a decent prefix?
	if buildCtx.GOROOT != "" {
		goroot := filepath.Join(buildCtx.GOROOT, "src")
		if p, ok := trim(path, filepath.ToSlash(goroot)); ok {
			return p
		}
	}
	for _, gopath := range splitGopath() {
		if p, ok := trim(path, filepath.ToSlash(gopath)); ok {
			return p
		}
	}
	return path
}

// trim trims the directory prefix from the path, paying attention
// to the path separator. If they are the same string or the prefix
// is not present the original is returned. The boolean reports whether
// the prefix is present. That path and prefix have slashes for separators.
func trim(path, prefix string) (string, bool) {
	if !strings.HasPrefix(path, prefix) {
		return path, false
	}
	if path == prefix {
		return path, true
	}
	if path[len(prefix)] == '/' {
		return path[len(prefix)+1:], true
	}
	return path, false // Textual prefix but not a path prefix.
}

// pkg.Fatalf is like log.Fatalf, but panics so it can be recovered in the
// main do function, so it doesn't cause an exit. Allows testing to work
// without running a subprocess. The log prefix will be added when
// logged in main; it is not added here.
func (pkg *Package) Fatalf(format string, args ...any) {
	panic(PackageError(fmt.Sprintf(format, args...)))
}

// parsePackage turns the build package we found into a parsed package
// we can then use to generate documentation.
func parsePackage(writer io.Writer, pkg *build.Package, userPath string) *Package {
	// include tells parser.ParseDir which files to include.
	// That means the file must be in the build package's GoFiles or CgoFiles
	// list only (no tag-ignored files, tests, swig or other non-Go files).
	include := func(info fs.FileInfo) bool {
		for _, name := range pkg.GoFiles {
			if name == info.Name() {
				return true
			}
		}
		for _, name := range pkg.CgoFiles {
			if name == info.Name() {
				return true
			}
		}
		return false
	}
	fset := token.NewFileSet()
	pkgs, err := parser.ParseDir(fset, pkg.Dir, include, parser.ParseComments)
	if err != nil {
		log.Fatal(err)
	}
	// Make sure they are all in one package.
	if len(pkgs) == 0 {
		log.Fatalf("no source-code package in directory %s", pkg.Dir)
	}
	if len(pkgs) > 1 {
		log.Fatalf("multiple packages in directory %s", pkg.Dir)
	}
	astPkg := pkgs[pkg.Name]

	// TODO: go/doc does not include typed constants in the constants
	// list, which is what we want. For instance, time.Sunday is of type
	// time.Weekday, so it is defined in the type but not in the
	// Consts list for the package. This prevents
	//	go doc time.Sunday
	// from finding the symbol. Work around this for now, but we
	// should fix it in go/doc.
	// A similar story applies to factory functions.
	mode := doc.AllDecls
	if showSrc {
		mode |= doc.PreserveAST // See comment for Package.emit.
	}
	docPkg := doc.New(astPkg, pkg.ImportPath, mode)
	typedValue := make(map[*doc.Value]bool)
	constructor := make(map[*doc.Func]bool)
	for _, typ := range docPkg.Types {
		docPkg.Consts = append(docPkg.Consts, typ.Consts...)
		docPkg.Vars = append(docPkg.Vars, typ.Vars...)
		docPkg.Funcs = append(docPkg.Funcs, typ.Funcs...)
		if isExported(typ.Name) {
			for _, value := range typ.Consts {
				typedValue[value] = true
			}
			for _, value := range typ.Vars {
				typedValue[value] = true
			}
			for _, fun := range typ.Funcs {
				// We don't count it as a constructor bound to the type
				// if the type itself is not exported.
				constructor[fun] = true
			}
		}
	}

	p := &Package{
		writer:      writer,
		name:        pkg.Name,
		userPath:    userPath,
		pkg:         astPkg,
		file:        ast.MergePackageFiles(astPkg, 0),
		doc:         docPkg,
		typedValue:  typedValue,
		constructor: constructor,
		build:       pkg,
		fs:          fset,
	}
	p.buf.pkg = p
	return p
}

func (pkg *Package) Printf(format string, args ...any) {
	fmt.Fprintf(&pkg.buf, format, args...)
}

func (pkg *Package) flush() {
	_, err := pkg.writer.Write(pkg.buf.Bytes())
	if err != nil {
		log.Fatal(err)
	}
	pkg.buf.Reset() // Not needed, but it's a flush.
}

var newlineBytes = []byte("\n\n") // We never ask for more than 2.

// newlines guarantees there are n newlines at the end of the buffer.
func (pkg *Package) newlines(n int) {
	for !bytes.HasSuffix(pkg.buf.Bytes(), newlineBytes[:n]) {
		pkg.buf.WriteRune('\n')
	}
}

// emit prints the node. If showSrc is true, it ignores the provided comment,
// assuming the comment is in the node itself. Otherwise, the go/doc package
// clears the stuff we don't want to print anyway. It's a bit of a magic trick.
func (pkg *Package) emit(comment string, node ast.Node) {
	if node != nil {
		var arg any = node
		if showSrc {
			// Need an extra little dance to get internal comments to appear.
			arg = &printer.CommentedNode{
				Node:     node,
				Comments: pkg.file.Comments,
			}
		}
		err := format.Node(&pkg.buf, pkg.fs, arg)
		if err != nil {
			log.Fatal(err)
		}
		if comment != "" && !showSrc {
			pkg.newlines(1)
			pkg.ToText(&pkg.buf, comment, indent, indent+indent)
			pkg.newlines(2) // Blank line after comment to separate from next item.
		} else {
			pkg.newlines(1)
		}
	}
}

// oneLineNode returns a one-line summary of the given input node.
func (pkg *Package) oneLineNode(node ast.Node) string {
	const maxDepth = 10
	return pkg.oneLineNodeDepth(node, maxDepth)
}

// oneLineNodeDepth returns a one-line summary of the given input node.
// The depth specifies the maximum depth when traversing the AST.
func (pkg *Package) oneLineNodeDepth(node ast.Node, depth int) string {
	const dotDotDot = "..."
	if depth == 0 {
		return dotDotDot
	}
	depth--

	switch n := node.(type) {
	case nil:
		return ""

	case *ast.GenDecl:
		// Formats const and var declarations.
		trailer := ""
		if len(n.Specs) > 1 {
			trailer = " " + dotDotDot
		}

		// Find the first relevant spec.
		typ := ""
		for i, spec := range n.Specs {
			valueSpec := spec.(*ast.ValueSpec) // Must succeed; we can't mix types in one GenDecl.

			// The type name may carry over from a previous specification in the
			// case of constants and iota.
			if valueSpec.Type != nil {
				typ = fmt.Sprintf(" %s", pkg.oneLineNodeDepth(valueSpec.Type, depth))
			} else if len(valueSpec.Values) > 0 {
				typ = ""
			}

			if !isExported(valueSpec.Names[0].Name) {
				continue
			}
			val := ""
			if i < len(valueSpec.Values) && valueSpec.Values[i] != nil {
				val = fmt.Sprintf(" = %s", pkg.oneLineNodeDepth(valueSpec.Values[i], depth))
			}
			return fmt.Sprintf("%s %s%s%s%s", n.Tok, valueSpec.Names[0], typ, val, trailer)
		}
		return ""

	case *ast.FuncDecl:
		// Formats func declarations.
		name := n.Name.Name
		recv := pkg.oneLineNodeDepth(n.Recv, depth)
		if len(recv) > 0 {
			recv = "(" + recv + ") "
		}
		fnc := pkg.oneLineNodeDepth(n.Type, depth)
		fnc = strings.TrimPrefix(fnc, "func")
		return fmt.Sprintf("func %s%s%s", recv, name, fnc)

	case *ast.TypeSpec:
		sep := " "
		if n.Assign.IsValid() {
			sep = " = "
		}
		tparams := pkg.formatTypeParams(n.TypeParams, depth)
		return fmt.Sprintf("type %s%s%s%s", n.Name.Name, tparams, sep, pkg.oneLineNodeDepth(n.Type, depth))

	case *ast.FuncType:
		var params []string
		if n.Params != nil {
			for _, field := range n.Params.List {
				params = append(params, pkg.oneLineField(field, depth))
			}
		}
		needParens := false
		var results []string
		if n.Results != nil {
			needParens = needParens || len(n.Results.List) > 1
			for _, field := range n.Results.List {
				needParens = needParens || len(field.Names) > 0
				results = append(results, pkg.oneLineField(field, depth))
			}
		}

		tparam := pkg.formatTypeParams(n.TypeParams, depth)
		param := joinStrings(params)
		if len(results) == 0 {
			return fmt.Sprintf("func%s(%s)", tparam, param)
		}
		result := joinStrings(results)
		if !needParens {
			return fmt.Sprintf("func%s(%s) %s", tparam, param, result)
		}
		return fmt.Sprintf("func%s(%s) (%s)", tparam, param, result)

	case *ast.StructType:
		if n.Fields == nil || len(n.Fields.List) == 0 {
			return "struct{}"
		}
		return "struct{ ... }"

	case *ast.InterfaceType:
		if n.Methods == nil || len(n.Methods.List) == 0 {
			return "interface{}"
		}
		return "interface{ ... }"

	case *ast.FieldList:
		if n == nil || len(n.List) == 0 {
			return ""
		}
		if len(n.List) == 1 {
			return pkg.oneLineField(n.List[0], depth)
		}
		return dotDotDot

	case *ast.FuncLit:
		return pkg.oneLineNodeDepth(n.Type, depth) + " { ... }"

	case *ast.CompositeLit:
		typ := pkg.oneLineNodeDepth(n.Type, depth)
		if len(n.Elts) == 0 {
			return fmt.Sprintf("%s{}", typ)
		}
		return fmt.Sprintf("%s{ %s }", typ, dotDotDot)

	case *ast.ArrayType:
		length := pkg.oneLineNodeDepth(n.Len, depth)
		element := pkg.oneLineNodeDepth(n.Elt, depth)
		return fmt.Sprintf("[%s]%s", length, element)

	case *ast.MapType:
		key := pkg.oneLineNodeDepth(n.Key, depth)
		value := pkg.oneLineNodeDepth(n.Value, depth)
		return fmt.Sprintf("map[%s]%s", key, value)

	case *ast.CallExpr:
		fnc := pkg.oneLineNodeDepth(n.Fun, depth)
		var args []string
		for _, arg := range n.Args {
			args = append(args, pkg.oneLineNodeDepth(arg, depth))
		}
		return fmt.Sprintf("%s(%s)", fnc, joinStrings(args))

	case *ast.UnaryExpr:
		return fmt.Sprintf("%s%s", n.Op, pkg.oneLineNodeDepth(n.X, depth))

	case *ast.Ident:
		return n.Name

	default:
		// As a fallback, use default formatter for all unknown node types.
		buf := new(bytes.Buffer)
		format.Node(buf, pkg.fs, node)
		s := buf.String()
		if strings.Contains(s, "\n") {
			return dotDotDot
		}
		return s
	}
}

func (pkg *Package) formatTypeParams(list *ast.FieldList, depth int) string {
	if list.NumFields() == 0 {
		return ""
	}
	var tparams []string
	for _, field := range list.List {
		tparams = append(tparams, pkg.oneLineField(field, depth))
	}
	return "[" + joinStrings(tparams) + "]"
}

// oneLineField returns a one-line summary of the field.
func (pkg *Package) oneLineField(field *ast.Field, depth int) string {
	var names []string
	for _, name := range field.Names {
		names = append(names, name.Name)
	}
	if len(names) == 0 {
		return pkg.oneLineNodeDepth(field.Type, depth)
	}
	return joinStrings(names) + " " + pkg.oneLineNodeDepth(field.Type, depth)
}

// joinStrings formats the input as a comma-separated list,
// but truncates the list at some reasonable length if necessary.
func joinStrings(ss []string) string {
	var n int
	for i, s := range ss {
		n += len(s) + len(", ")
		if n > punchedCardWidth {
			ss = append(ss[:i:i], "...")
			break
		}
	}
	return strings.Join(ss, ", ")
}

// allDoc prints all the docs for the package.
func (pkg *Package) allDoc() {
	pkg.Printf("") // Trigger the package clause; we know the package exists.
	pkg.ToText(&pkg.buf, pkg.doc.Doc, "", indent)
	pkg.newlines(1)

	printed := make(map[*ast.GenDecl]bool)

	hdr := ""
	printHdr := func(s string) {
		if hdr != s {
			pkg.Printf("\n%s\n\n", s)
			hdr = s
		}
	}

	// Constants.
	for _, value := range pkg.doc.Consts {
		// Constants and variables come in groups, and valueDoc prints
		// all the items in the group. We only need to find one exported symbol.
		for _, name := range value.Names {
			if isExported(name) && !pkg.typedValue[value] {
				printHdr("CONSTANTS")
				pkg.valueDoc(value, printed)
				break
			}
		}
	}

	// Variables.
	for _, value := range pkg.doc.Vars {
		// Constants and variables come in groups, and valueDoc prints
		// all the items in the group. We only need to find one exported symbol.
		for _, name := range value.Names {
			if isExported(name) && !pkg.typedValue[value] {
				printHdr("VARIABLES")
				pkg.valueDoc(value, printed)
				break
			}
		}
	}

	// Functions.
	for _, fun := range pkg.doc.Funcs {
		if isExported(fun.Name) && !pkg.constructor[fun] {
			printHdr("FUNCTIONS")
			pkg.emit(fun.Doc, fun.Decl)
		}
	}

	// Types.
	for _, typ := range pkg.doc.Types {
		if isExported(typ.Name) {
			printHdr("TYPES")
			pkg.typeDoc(typ)
		}
	}
}

// packageDoc prints the docs for the package (package doc plus one-liners of the rest).
func (pkg *Package) packageDoc() {
	pkg.Printf("") // Trigger the package clause; we know the package exists.
	if !short {
		pkg.ToText(&pkg.buf, pkg.doc.Doc, "", indent)
		pkg.newlines(1)
	}

	if pkg.pkg.Name == "main" && !showCmd {
		// Show only package docs for commands.
		return
	}

	if !short {
		pkg.newlines(2) // Guarantee blank line before the components.
	}

	pkg.valueSummary(pkg.doc.Consts, false)
	pkg.valueSummary(pkg.doc.Vars, false)
	pkg.funcSummary(pkg.doc.Funcs, false)
	pkg.typeSummary()
	if !short {
		pkg.bugs()
	}
}

// packageClause prints the package clause.
func (pkg *Package) packageClause() {
	if short {
		return
	}
	importPath := pkg.build.ImportComment
	if importPath == "" {
		importPath = pkg.build.ImportPath
	}

	// If we're using modules, the import path derived from module code locations wins.
	// If we did a file system scan, we knew the import path when we found the directory.
	// But if we started with a directory name, we never knew the import path.
	// Either way, we don't know it now, and it's cheap to (re)compute it.
	if usingModules {
		for _, root := range codeRoots() {
			if pkg.build.Dir == root.dir {
				importPath = root.importPath
				break
			}
			if strings.HasPrefix(pkg.build.Dir, root.dir+string(filepath.Separator)) {
				suffix := filepath.ToSlash(pkg.build.Dir[len(root.dir)+1:])
				if root.importPath == "" {
					importPath = suffix
				} else {
					importPath = root.importPath + "/" + suffix
				}
				break
			}
		}
	}

	pkg.Printf("package %s // import %q\n\n", pkg.name, importPath)
	if !usingModules && importPath != pkg.build.ImportPath {
		pkg.Printf("WARNING: package source is installed in %q\n", pkg.build.ImportPath)
	}
}

// valueSummary prints a one-line summary for each set of values and constants.
// If all the types in a constant or variable declaration belong to the same
// type they can be printed by typeSummary, and so can be suppressed here.
func (pkg *Package) valueSummary(values []*doc.Value, showGrouped bool) {
	var isGrouped map[*doc.Value]bool
	if !showGrouped {
		isGrouped = make(map[*doc.Value]bool)
		for _, typ := range pkg.doc.Types {
			if !isExported(typ.Name) {
				continue
			}
			for _, c := range typ.Consts {
				isGrouped[c] = true
			}
			for _, v := range typ.Vars {
				isGrouped[v] = true
			}
		}
	}

	for _, value := range values {
		if !isGrouped[value] {
			if decl := pkg.oneLineNode(value.Decl); decl != "" {
				pkg.Printf("%s\n", decl)
			}
		}
	}
}

// funcSummary prints a one-line summary for each function. Constructors
// are printed by typeSummary, below, and so can be suppressed here.
func (pkg *Package) funcSummary(funcs []*doc.Func, showConstructors bool) {
	for _, fun := range funcs {
		// Exported functions only. The go/doc package does not include methods here.
		if isExported(fun.Name) {
			if showConstructors || !pkg.constructor[fun] {
				pkg.Printf("%s\n", pkg.oneLineNode(fun.Decl))
			}
		}
	}
}

// typeSummary prints a one-line summary for each type, followed by its constructors.
func (pkg *Package) typeSummary() {
	for _, typ := range pkg.doc.Types {
		for _, spec := range typ.Decl.Specs {
			typeSpec := spec.(*ast.TypeSpec) // Must succeed.
			if isExported(typeSpec.Name.Name) {
				pkg.Printf("%s\n", pkg.oneLineNode(typeSpec))
				// Now print the consts, vars, and constructors.
				for _, c := range typ.Consts {
					if decl := pkg.oneLineNode(c.Decl); decl != "" {
						pkg.Printf(indent+"%s\n", decl)
					}
				}
				for _, v := range typ.Vars {
					if decl := pkg.oneLineNode(v.Decl); decl != "" {
						pkg.Printf(indent+"%s\n", decl)
					}
				}
				for _, constructor := range typ.Funcs {
					if isExported(constructor.Name) {
						pkg.Printf(indent+"%s\n", pkg.oneLineNode(constructor.Decl))
					}
				}
			}
		}
	}
}

// bugs prints the BUGS information for the package.
// TODO: Provide access to TODOs and NOTEs as well (very noisy so off by default)?
func (pkg *Package) bugs() {
	if pkg.doc.Notes["BUG"] == nil {
		return
	}
	pkg.Printf("\n")
	for _, note := range pkg.doc.Notes["BUG"] {
		pkg.Printf("%s: %v\n", "BUG", note.Body)
	}
}

// findValues finds the doc.Values that describe the symbol.
func (pkg *Package) findValues(symbol string, docValues []*doc.Value) (values []*doc.Value) {
	for _, value := range docValues {
		for _, name := range value.Names {
			if match(symbol, name) {
				values = append(values, value)
			}
		}
	}
	return
}

// findFuncs finds the doc.Funcs that describes the symbol.
func (pkg *Package) findFuncs(symbol string) (funcs []*doc.Func) {
	for _, fun := range pkg.doc.Funcs {
		if match(symbol, fun.Name) {
			funcs = append(funcs, fun)
		}
	}
	return
}

// findTypes finds the doc.Types that describes the symbol.
// If symbol is empty, it finds all exported types.
func (pkg *Package) findTypes(symbol string) (types []*doc.Type) {
	for _, typ := range pkg.doc.Types {
		if symbol == "" && isExported(typ.Name) || match(symbol, typ.Name) {
			types = append(types, typ)
		}
	}
	return
}

// findTypeSpec returns the ast.TypeSpec within the declaration that defines the symbol.
// The name must match exactly.
func (pkg *Package) findTypeSpec(decl *ast.GenDecl, symbol string) *ast.TypeSpec {
	for _, spec := range decl.Specs {
		typeSpec := spec.(*ast.TypeSpec) // Must succeed.
		if symbol == typeSpec.Name.Name {
			return typeSpec
		}
	}
	return nil
}

// symbolDoc prints the docs for symbol. There may be multiple matches.
// If symbol matches a type, output includes its methods factories and associated constants.
// If there is no top-level symbol, symbolDoc looks for methods that match.
func (pkg *Package) symbolDoc(symbol string) bool {
	found := false
	// Functions.
	for _, fun := range pkg.findFuncs(symbol) {
		// Symbol is a function.
		decl := fun.Decl
		pkg.emit(fun.Doc, decl)
		found = true
	}
	// Constants and variables behave the same.
	values := pkg.findValues(symbol, pkg.doc.Consts)
	values = append(values, pkg.findValues(symbol, pkg.doc.Vars)...)
	// A declaration like
	//	const ( c = 1; C = 2 )
	// could be printed twice if the -u flag is set, as it matches twice.
	// So we remember which declarations we've printed to avoid duplication.
	printed := make(map[*ast.GenDecl]bool)
	for _, value := range values {
		pkg.valueDoc(value, printed)
		found = true
	}
	// Types.
	for _, typ := range pkg.findTypes(symbol) {
		pkg.typeDoc(typ)
		found = true
	}
	if !found {
		// See if there are methods.
		if !pkg.printMethodDoc("", symbol) {
			return false
		}
	}
	return true
}

// valueDoc prints the docs for a constant or variable.
func (pkg *Package) valueDoc(value *doc.Value, printed map[*ast.GenDecl]bool) {
	if printed[value.Decl] {
		return
	}
	// Print each spec only if there is at least one exported symbol in it.
	// (See issue 11008.)
	// TODO: Should we elide unexported symbols from a single spec?
	// It's an unlikely scenario, probably not worth the trouble.
	// TODO: Would be nice if go/doc did this for us.
	specs := make([]ast.Spec, 0, len(value.Decl.Specs))
	var typ ast.Expr
	for _, spec := range value.Decl.Specs {
		vspec := spec.(*ast.ValueSpec)

		// The type name may carry over from a previous specification in the
		// case of constants and iota.
		if vspec.Type != nil {
			typ = vspec.Type
		}

		for _, ident := range vspec.Names {
			if showSrc || isExported(ident.Name) {
				if vspec.Type == nil && vspec.Values == nil && typ != nil {
					// This a standalone identifier, as in the case of iota usage.
					// Thus, assume the type comes from the previous type.
					vspec.Type = &ast.Ident{
						Name:    pkg.oneLineNode(typ),
						NamePos: vspec.End() - 1,
					}
				}

				specs = append(specs, vspec)
				typ = nil // Only inject type on first exported identifier
				break
			}
		}
	}
	if len(specs) == 0 {
		return
	}
	value.Decl.Specs = specs
	pkg.emit(value.Doc, value.Decl)
	printed[value.Decl] = true
}

// typeDoc prints the docs for a type, including constructors and other items
// related to it.
func (pkg *Package) typeDoc(typ *doc.Type) {
	decl := typ.Decl
	spec := pkg.findTypeSpec(decl, typ.Name)
	trimUnexportedElems(spec)
	// If there are multiple types defined, reduce to just this one.
	if len(decl.Specs) > 1 {
		decl.Specs = []ast.Spec{spec}
	}
	pkg.emit(typ.Doc, decl)
	pkg.newlines(2)
	// Show associated methods, constants, etc.
	if showAll {
		printed := make(map[*ast.GenDecl]bool)
		// We can use append here to print consts, then vars. Ditto for funcs and methods.
		values := typ.Consts
		values = append(values, typ.Vars...)
		for _, value := range values {
			for _, name := range value.Names {
				if isExported(name) {
					pkg.valueDoc(value, printed)
					break
				}
			}
		}
		funcs := typ.Funcs
		funcs = append(funcs, typ.Methods...)
		for _, fun := range funcs {
			if isExported(fun.Name) {
				pkg.emit(fun.Doc, fun.Decl)
				if fun.Doc == "" {
					pkg.newlines(2)
				}
			}
		}
	} else {
		pkg.valueSummary(typ.Consts, true)
		pkg.valueSummary(typ.Vars, true)
		pkg.funcSummary(typ.Funcs, true)
		pkg.funcSummary(typ.Methods, true)
	}
}

// trimUnexportedElems modifies spec in place to elide unexported fields from
// structs and methods from interfaces (unless the unexported flag is set or we
// are asked to show the original source).
func trimUnexportedElems(spec *ast.TypeSpec) {
	if unexported || showSrc {
		return
	}
	switch typ := spec.Type.(type) {
	case *ast.StructType:
		typ.Fields = trimUnexportedFields(typ.Fields, false)
	case *ast.InterfaceType:
		typ.Methods = trimUnexportedFields(typ.Methods, true)
	}
}

// trimUnexportedFields returns the field list trimmed of unexported fields.
func trimUnexportedFields(fields *ast.FieldList, isInterface bool) *ast.FieldList {
	what := "methods"
	if !isInterface {
		what = "fields"
	}

	trimmed := false
	list := make([]*ast.Field, 0, len(fields.List))
	for _, field := range fields.List {
		names := field.Names
		if len(names) == 0 {
			// Embedded type. Use the name of the type. It must be of the form ident or
			// pkg.ident (for structs and interfaces), or *ident or *pkg.ident (structs only).
			// Or a type embedded in a constraint.
			// Nothing else is allowed.
			ty := field.Type
			if se, ok := field.Type.(*ast.StarExpr); !isInterface && ok {
				// The form *ident or *pkg.ident is only valid on
				// embedded types in structs.
				ty = se.X
			}
			constraint := false
			switch ident := ty.(type) {
			case *ast.Ident:
				if isInterface && ident.Name == "error" && ident.Obj == nil {
					// For documentation purposes, we consider the builtin error
					// type special when embedded in an interface, such that it
					// always gets shown publicly.
					list = append(list, field)
					continue
				}
				names = []*ast.Ident{ident}
			case *ast.SelectorExpr:
				// An embedded type may refer to a type in another package.
				names = []*ast.Ident{ident.Sel}
			default:
				// An approximation or union or type
				// literal in an interface.
				constraint = true
			}
			if names == nil && !constraint {
				// Can only happen if AST is incorrect. Safe to continue with a nil list.
				log.Print("invalid program: unexpected type for embedded field")
			}
		}
		// Trims if any is unexported. Good enough in practice.
		ok := true
		for _, name := range names {
			if !isExported(name.Name) {
				trimmed = true
				ok = false
				break
			}
		}
		if ok {
			list = append(list, field)
		}
	}
	if !trimmed {
		return fields
	}
	unexportedField := &ast.Field{
		Type: &ast.Ident{
			// Hack: printer will treat this as a field with a named type.
			// Setting Name and NamePos to ("", fields.Closing-1) ensures that
			// when Pos and End are called on this field, they return the
			// position right before closing '}' character.
			Name:    "",
			NamePos: fields.Closing - 1,
		},
		Comment: &ast.CommentGroup{
			List: []*ast.Comment{{Text: fmt.Sprintf("// Has unexported %s.\n", what)}},
		},
	}
	return &ast.FieldList{
		Opening: fields.Opening,
		List:    append(list, unexportedField),
		Closing: fields.Closing,
	}
}

// printMethodDoc prints the docs for matches of symbol.method.
// If symbol is empty, it prints all methods for any concrete type
// that match the name. It reports whether it found any methods.
func (pkg *Package) printMethodDoc(symbol, method string) bool {
	types := pkg.findTypes(symbol)
	if types == nil {
		if symbol == "" {
			return false
		}
		pkg.Fatalf("symbol %s is not a type in package %s installed in %q", symbol, pkg.name, pkg.build.ImportPath)
	}
	found := false
	for _, typ := range types {
		if len(typ.Methods) > 0 {
			for _, meth := range typ.Methods {
				if match(method, meth.Name) {
					decl := meth.Decl
					pkg.emit(meth.Doc, decl)
					found = true
				}
			}
			continue
		}
		if symbol == "" {
			continue
		}
		// Type may be an interface. The go/doc package does not attach
		// an interface's methods to the doc.Type. We need to dig around.
		spec := pkg.findTypeSpec(typ.Decl, typ.Name)
		inter, ok := spec.Type.(*ast.InterfaceType)
		if !ok {
			// Not an interface type.
			continue
		}

		// Collect and print only the methods that match.
		var methods []*ast.Field
		for _, iMethod := range inter.Methods.List {
			// This is an interface, so there can be only one name.
			// TODO: Anonymous methods (embedding)
			if len(iMethod.Names) == 0 {
				continue
			}
			name := iMethod.Names[0].Name
			if match(method, name) {
				methods = append(methods, iMethod)
				found = true
			}
		}
		if found {
			pkg.Printf("type %s ", spec.Name)
			inter.Methods.List, methods = methods, inter.Methods.List
			err := format.Node(&pkg.buf, pkg.fs, inter)
			if err != nil {
				log.Fatal(err)
			}
			pkg.newlines(1)
			// Restore the original methods.
			inter.Methods.List = methods
		}
	}
	return found
}

// printFieldDoc prints the docs for matches of symbol.fieldName.
// It reports whether it found any field.
// Both symbol and fieldName must be non-empty or it returns false.
func (pkg *Package) printFieldDoc(symbol, fieldName string) bool {
	if symbol == "" || fieldName == "" {
		return false
	}
	types := pkg.findTypes(symbol)
	if types == nil {
		pkg.Fatalf("symbol %s is not a type in package %s installed in %q", symbol, pkg.name, pkg.build.ImportPath)
	}
	found := false
	numUnmatched := 0
	for _, typ := range types {
		// Type must be a struct.
		spec := pkg.findTypeSpec(typ.Decl, typ.Name)
		structType, ok := spec.Type.(*ast.StructType)
		if !ok {
			// Not a struct type.
			continue
		}
		for _, field := range structType.Fields.List {
			// TODO: Anonymous fields.
			for _, name := range field.Names {
				if !match(fieldName, name.Name) {
					numUnmatched++
					continue
				}
				if !found {
					pkg.Printf("type %s struct {\n", typ.Name)
				}
				if field.Doc != nil {
					// To present indented blocks in comments correctly, process the comment as
					// a unit before adding the leading // to each line.
					docBuf := new(bytes.Buffer)
					pkg.ToText(docBuf, field.Doc.Text(), "", indent)
					scanner := bufio.NewScanner(docBuf)
					for scanner.Scan() {
						fmt.Fprintf(&pkg.buf, "%s// %s\n", indent, scanner.Bytes())
					}
				}
				s := pkg.oneLineNode(field.Type)
				lineComment := ""
				if field.Comment != nil {
					lineComment = fmt.Sprintf("  %s", field.Comment.List[0].Text)
				}
				pkg.Printf("%s%s %s%s\n", indent, name, s, lineComment)
				found = true
			}
		}
	}
	if found {
		if numUnmatched > 0 {
			pkg.Printf("\n    // ... other fields elided ...\n")
		}
		pkg.Printf("}\n")
	}
	return found
}

// methodDoc prints the docs for matches of symbol.method.
func (pkg *Package) methodDoc(symbol, method string) bool {
	return pkg.printMethodDoc(symbol, method)
}

// fieldDoc prints the docs for matches of symbol.field.
func (pkg *Package) fieldDoc(symbol, field string) bool {
	return pkg.printFieldDoc(symbol, field)
}

// match reports whether the user's symbol matches the program's.
// A lower-case character in the user's string matches either case in the program's.
// The program string must be exported.
func match(user, program string) bool {
	if !isExported(program) {
		return false
	}
	if matchCase {
		return user == program
	}
	for _, u := range user {
		p, w := utf8.DecodeRuneInString(program)
		program = program[w:]
		if u == p {
			continue
		}
		if unicode.IsLower(u) && simpleFold(u) == simpleFold(p) {
			continue
		}
		return false
	}
	return program == ""
}

// simpleFold returns the minimum rune equivalent to r
// under Unicode-defined simple case folding.
func simpleFold(r rune) rune {
	for {
		r1 := unicode.SimpleFold(r)
		if r1 <= r {
			return r1 // wrapped around, found min
		}
		r = r1
	}
}

最后修改 March 10, 2024: 更新 (ddf4687)