parse and print comments from go source file.

gcmt.go

package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"os"
	"path/filepath"
	"strings"
	"sync"
)

func printUsage() {
	_, _ = fmt.Fprintf(os.Stderr, "Usage: %s <directory>\n", os.Args[0])
}

func printError(err error) {
	_, _ = fmt.Fprintf(os.Stderr, "error: %v", err)
	fmt.Fprintln(os.Stderr)
	fmt.Fprintln(os.Stderr)
	printUsage()

	os.Exit(1)
}

func main() {
	if len(os.Args) < 2 {
		printError(fmt.Errorf("<directory> must be given"))
	}

	base := os.Args[1]
	if fi, err := os.Stat(base); os.IsNotExist(err) {
		printError(err)
	} else if !fi.IsDir() {
		printError(fmt.Errorf("%s is not directory", base))
	}

	directories := map[string]struct{}{}
	err := filepath.Walk(base, func(path string, fi os.FileInfo, err error) error {
		if fi.IsDir() {
			return nil
		}
		if !strings.HasSuffix(fi.Name(), ".go") {
			return nil
		}

		d := filepath.Dir(path)
		if _, found := directories[d]; found {
			return nil
		}

		directories[d] = struct{}{}

		return nil
	})
	if err != nil {
		printError(err)
	}

	var wg sync.WaitGroup
	wg.Add(len(directories))

	ch := make(chan func())
	for d := range directories {
		go func(d string) {
			if f, err := parse(d, base); err != nil {
				printError(err)

				os.Exit(1)
			} else {
				ch <- f
			}

			wg.Done()
		}(d)
	}

	go func() {
		wg.Wait()

		close(ch)
	}()

	var i int
	for f := range ch {
		f()
		i++
	}

	os.Exit(0)
}

func parse(directory, base string) (func(), error) {
	fset := token.NewFileSet()
	packages, err := parser.ParseDir(
		fset,
		directory,
		func(os.FileInfo) bool {
			return true
		},
		parser.ParseComments,
	)
	if err != nil {
		return nil, err
	}

	return func() {
		print(packages, fset, base)
	}, nil
}

func print(packages map[string]*ast.Package, fset *token.FileSet, base string) {
	for _, p := range packages {
		for filename, f := range p.Files {
			for _, cg := range f.Comments {
				for _, c := range cg.List {
					s := strings.Replace(c.Text, "\n", " ", -1)

					rel, _ := filepath.Rel(base, filename)
					fmt.Fprintf(
						os.Stdout,
						"%s:%d: %s\n",
						rel,
						fset.Position(c.Pos()).Line,
						strings.TrimSpace(s),
					)
				}
			}
		}
	}
}