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