printer
原文：https://pkg.go.dev/go/printer@go1.23.0
Package printer implements printing of AST nodes.
Package printer 实现 AST 节点的打印。
常量
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变量
This section is empty.
函数
func Fprint
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| func Fprint(output io.Writer, fset *token.FileSet, node any) error
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Fprint “pretty-prints” an AST node to output. It calls Config.Fprint with default settings. Note that gofmt uses tabs for indentation but spaces for alignment; use format.Node (package go/format) for output that matches gofmt.
Fprint 将 AST 节点“漂亮地打印”到输出。它使用默认设置调用 Config.Fprint。请注意，gofmt 使用制表符进行缩进，但使用空格进行对齐；使用 format.Node（包 go/format）以获得与 gofmt 匹配的输出。
Fprint Example
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| package main
import (
"bytes"
"fmt"
"go/ast"
"go/parser"
"go/printer"
"go/token"
"strings"
)
func parseFunc(filename, functionname string) (fun *ast.FuncDecl, fset *token.FileSet) {
fset = token.NewFileSet()
if file, err := parser.ParseFile(fset, filename, nil, 0); err == nil {
for _, d := range file.Decls {
if f, ok := d.(*ast.FuncDecl); ok && f.Name.Name == functionname {
fun = f
return
}
}
}
panic("function not found")
}
func printSelf() {
// Parse source file and extract the AST without comments for
// this function, with position information referring to the
// file set fset.
funcAST, fset := parseFunc("example_test.go", "printSelf")
// Print the function body into buffer buf.
// The file set is provided to the printer so that it knows
// about the original source formatting and can add additional
// line breaks where they were present in the source.
var buf bytes.Buffer
printer.Fprint(&buf, fset, funcAST.Body)
// Remove braces {} enclosing the function body, unindent,
// and trim leading and trailing white space.
s := buf.String()
s = s[1 : len(s)-1]
s = strings.TrimSpace(strings.ReplaceAll(s, "\n\t", "\n"))
// Print the cleaned-up body text to stdout.
fmt.Println(s)
}
func main() {
printSelf()
}
Output:
funcAST, fset := parseFunc("example_test.go", "printSelf")
var buf bytes.Buffer
printer.Fprint(&buf, fset, funcAST.Body)
s := buf.String()
s = s[1 : len(s)-1]
s = strings.TrimSpace(strings.ReplaceAll(s, "\n\t", "\n"))
fmt.Println(s)
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类型
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| type CommentedNode struct {
Node any // *ast.File, or ast.Expr, ast.Decl, ast.Spec, or ast.Stmt
Comments []*ast.CommentGroup
}
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A CommentedNode bundles an AST node and corresponding comments. It may be provided as argument to any of the Fprint functions.
CommentedNode 捆绑了一个 AST 节点和相应的注释。它可以作为任何 Fprint 函数的参数提供。
type Config
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| type Config struct {
Mode Mode // default: 0
Tabwidth int // default: 8
Indent int // default: 0 (all code is indented at least by this much)
}
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A Config node controls the output of Fprint.
Config 节点控制 Fprint 的输出。
(*Config) Fprint
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| func (cfg *Config) Fprint(output io.Writer, fset *token.FileSet, node any) error
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Fprint “pretty-prints” an AST node to output for a given configuration cfg. Position information is interpreted relative to the file set fset. The node type must be *ast.File, *CommentedNode, []ast.Decl, []ast.Stmt, or assignment-compatible to ast.Expr, ast.Decl, ast.Spec, or ast.Stmt.
Fprint “漂亮地打印”一个 AST 节点，以针对给定配置 cfg 输出。位置信息相对于文件集 fset 解释。节点类型必须是 *ast.File、*CommentedNode、[]ast.Decl、[]ast.Stmt 或与 ast.Expr、ast.Decl、ast.Spec 或 ast.Stmt 兼容的赋值。
type Mode
A Mode value is a set of flags (or 0). They control printing.
Mode 值是一组标志（或 0）。它们控制打印。
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| const (
RawFormat Mode = 1 << iota // do not use a tabwriter; if set, UseSpaces is ignored
TabIndent // use tabs for indentation independent of UseSpaces
UseSpaces // use spaces instead of tabs for alignment
SourcePos // emit //line directives to preserve original source positions
)
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