cmd/go/internal/fsys: add Glob

Glob is needed for //go:embed processing.

Also change TestReadDir to be deterministic
and print more output about failures.

Change-Id: Ie22a9c5b32bda753579ff98cec1d28e3244c4e06
Reviewed-on: https://go-review.googlesource.com/c/go/+/264538
Trust: Russ Cox <[email protected]>
Trust: Jay Conrod <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>

Author: rsc

src/cmd/go/internal/fsys/fsys.go

@@ -10,6 +10,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 	"sort"
 	"strings"
 	"time"
@@ -514,3 +515,165 @@ func (f fakeDir) Mode() fs.FileMode  { return fs.ModeDir | 0500 }
 func (f fakeDir) ModTime() time.Time { return time.Unix(0, 0) }
 func (f fakeDir) IsDir() bool        { return true }
 func (f fakeDir) Sys() interface{}   { return nil }
+
+// Glob is like filepath.Glob but uses the overlay file system.
+func Glob(pattern string) (matches []string, err error) {
+	// Check pattern is well-formed.
+	if _, err := filepath.Match(pattern, ""); err != nil {
+		return nil, err
+	}
+	if !hasMeta(pattern) {
+		if _, err = lstat(pattern); err != nil {
+			return nil, nil
+		}
+		return []string{pattern}, nil
+	}
+
+	dir, file := filepath.Split(pattern)
+	volumeLen := 0
+	if runtime.GOOS == "windows" {
+		volumeLen, dir = cleanGlobPathWindows(dir)
+	} else {
+		dir = cleanGlobPath(dir)
+	}
+
+	if !hasMeta(dir[volumeLen:]) {
+		return glob(dir, file, nil)
+	}
+
+	// Prevent infinite recursion. See issue 15879.
+	if dir == pattern {
+		return nil, filepath.ErrBadPattern
+	}
+
+	var m []string
+	m, err = Glob(dir)
+	if err != nil {
+		return
+	}
+	for _, d := range m {
+		matches, err = glob(d, file, matches)
+		if err != nil {
+			return
+		}
+	}
+	return
+}
+
+// cleanGlobPath prepares path for glob matching.
+func cleanGlobPath(path string) string {
+	switch path {
+	case "":
+		return "."
+	case string(filepath.Separator):
+		// do nothing to the path
+		return path
+	default:
+		return path[0 : len(path)-1] // chop off trailing separator
+	}
+}
+
+func volumeNameLen(path string) int {
+	isSlash := func(c uint8) bool {
+		return c == '\\' || c == '/'
+	}
+	if len(path) < 2 {
+		return 0
+	}
+	// with drive letter
+	c := path[0]
+	if path[1] == ':' && ('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
+		return 2
+	}
+	// is it UNC? https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
+	if l := len(path); l >= 5 && isSlash(path[0]) && isSlash(path[1]) &&
+		!isSlash(path[2]) && path[2] != '.' {
+		// first, leading `\\` and next shouldn't be `\`. its server name.
+		for n := 3; n < l-1; n++ {
+			// second, next '\' shouldn't be repeated.
+			if isSlash(path[n]) {
+				n++
+				// third, following something characters. its share name.
+				if !isSlash(path[n]) {
+					if path[n] == '.' {
+						break
+					}
+					for ; n < l; n++ {
+						if isSlash(path[n]) {
+							break
+						}
+					}
+					return n
+				}
+				break
+			}
+		}
+	}
+	return 0
+}
+
+// cleanGlobPathWindows is windows version of cleanGlobPath.
+func cleanGlobPathWindows(path string) (prefixLen int, cleaned string) {
+	vollen := volumeNameLen(path)
+	switch {
+	case path == "":
+		return 0, "."
+	case vollen+1 == len(path) && os.IsPathSeparator(path[len(path)-1]): // /, \, C:\ and C:/
+		// do nothing to the path
+		return vollen + 1, path
+	case vollen == len(path) && len(path) == 2: // C:
+		return vollen, path + "." // convert C: into C:.
+	default:
+		if vollen >= len(path) {
+			vollen = len(path) - 1
+		}
+		return vollen, path[0 : len(path)-1] // chop off trailing separator
+	}
+}
+
+// glob searches for files matching pattern in the directory dir
+// and appends them to matches. If the directory cannot be
+// opened, it returns the existing matches. New matches are
+// added in lexicographical order.
+func glob(dir, pattern string, matches []string) (m []string, e error) {
+	m = matches
+	fi, err := Stat(dir)
+	if err != nil {
+		return // ignore I/O error
+	}
+	if !fi.IsDir() {
+		return // ignore I/O error
+	}
+
+	list, err := ReadDir(dir)
+	if err != nil {
+		return // ignore I/O error
+	}
+
+	var names []string
+	for _, info := range list {
+		names = append(names, info.Name())
+	}
+	sort.Strings(names)
+
+	for _, n := range names {
+		matched, err := filepath.Match(pattern, n)
+		if err != nil {
+			return m, err
+		}
+		if matched {
+			m = append(m, filepath.Join(dir, n))
+		}
+	}
+	return
+}
+
+// hasMeta reports whether path contains any of the magic characters
+// recognized by filepath.Match.
+func hasMeta(path string) bool {
+	magicChars := `*?[`
+	if runtime.GOOS != "windows" {
+		magicChars = `*?[\`
+	}
+	return strings.ContainsAny(path, magicChars)
+}