1 files changed, 116 insertions, 0 deletions
diff --git a/src/go/doc/headscan.go b/src/go/doc/headscan.go
new file mode 100644
index 0000000..28cb84f
--- /dev/null
+++ b/src/go/doc/headscan.go
@@ -0,0 +1,116 @@
+// Copyright 2011 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.
+
+//go:build ignore
+// +build ignore
+
+/*
+	The headscan command extracts comment headings from package files;
+	it is used to detect false positives which may require an adjustment
+	to the comment formatting heuristics in comment.go.
+
+	Usage: headscan [-root root_directory]
+
+	By default, the $GOROOT/src directory is scanned.
+*/
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/doc"
+	"go/parser"
+	"go/token"
+	"internal/lazyregexp"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+var (
+	root    = flag.String("root", filepath.Join(runtime.GOROOT(), "src"), "root of filesystem tree to scan")
+	verbose = flag.Bool("v", false, "verbose mode")
+)
+
+// ToHTML in comment.go assigns a (possibly blank) ID to each heading
+var html_h = lazyregexp.New(`<h3 id="[^"]*">`)
+
+const html_endh = "</h3>\n"
+
+func isGoFile(fi fs.FileInfo) bool {
+	return strings.HasSuffix(fi.Name(), ".go") &&
+		!strings.HasSuffix(fi.Name(), "_test.go")
+}
+
+func appendHeadings(list []string, comment string) []string {
+	var buf bytes.Buffer
+	doc.ToHTML(&buf, comment, nil)
+	for s := buf.String(); ; {
+		loc := html_h.FindStringIndex(s)
+		if len(loc) == 0 {
+			break
+		}
+		i := loc[1]
+		j := strings.Index(s, html_endh)
+		if j < 0 {
+			list = append(list, s[i:]) // incorrect HTML
+			break
+		}
+		list = append(list, s[i:j])
+		s = s[j+len(html_endh):]
+	}
+	return list
+}
+
+func main() {
+	flag.Parse()
+	fset := token.NewFileSet()
+	nheadings := 0
+	err := filepath.WalkDir(*root, func(path string, info fs.DirEntry, err error) error {
+		if !info.IsDir() {
+			return nil
+		}
+		pkgs, err := parser.ParseDir(fset, path, isGoFile, parser.ParseComments)
+		if err != nil {
+			if *verbose {
+				fmt.Fprintln(os.Stderr, err)
+			}
+			return nil
+		}
+		for _, pkg := range pkgs {
+			d := doc.New(pkg, path, doc.Mode(0))
+			list := appendHeadings(nil, d.Doc)
+			for _, d := range d.Consts {
+				list = appendHeadings(list, d.Doc)
+			}
+			for _, d := range d.Types {
+				list = appendHeadings(list, d.Doc)
+			}
+			for _, d := range d.Vars {
+				list = appendHeadings(list, d.Doc)
+			}
+			for _, d := range d.Funcs {
+				list = appendHeadings(list, d.Doc)
+			}
+			if len(list) > 0 {
+				// directories may contain multiple packages;
+				// print path and package name
+				fmt.Printf("%s (package %s)\n", path, pkg.Name)
+				for _, h := range list {
+					fmt.Printf("\t%s\n", h)
+				}
+				nheadings += len(list)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	fmt.Println(nheadings, "headings found")
+}