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Source file src/go/printer/example_test.go

Documentation: go/printer

  // Copyright 2012 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 printer_test
  
  import (
  	"bytes"
  	"fmt"
  	"go/ast"
  	"go/parser"
  	"go/printer"
  	"go/token"
  	"strings"
  	"testing"
  )
  
  // Dummy test function so that godoc does not use the entire file as example.
  func Test(*testing.T) {}
  
  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 ExampleFprint() {
  	// 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", "ExampleFprint")
  
  	// 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.Replace(s, "\n\t", "\n", -1))
  
  	// Print the cleaned-up body text to stdout.
  	fmt.Println(s)
  
  	// output:
  	// funcAST, fset := parseFunc("example_test.go", "ExampleFprint")
  	//
  	// var buf bytes.Buffer
  	// printer.Fprint(&buf, fset, funcAST.Body)
  	//
  	// s := buf.String()
  	// s = s[1 : len(s)-1]
  	// s = strings.TrimSpace(strings.Replace(s, "\n\t", "\n", -1))
  	//
  	// fmt.Println(s)
  }
  

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