Documentation
¶
Overview ¶
Package printer implements printing of AST nodes.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Fprint ¶
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.
Example ¶
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)
Types ¶
type CommentedNode ¶
type CommentedNode struct {
Node any // *ast.File, or ast.Expr, ast.Decl, ast.Spec, or ast.Stmt
Comments []*ast.CommentGroup
}
A CommentedNode bundles an AST node and corresponding comments. It may be provided as argument to any of the Fprint functions.
type Config ¶
type Config struct {
Mode Mode // default: 0
Tabwidth int // default: 8
Indent int // default: 0 (all code is indented at least by this much)
}
A Config node controls the output of Fprint.
func (*Config) Fprint ¶
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.
Source Files