feat: Add EvalSymlinks to fix link related tests

eval_symlink.go

@@ -0,0 +1,12 @@
+package fs
+
+// evalSymlinks returns the path name after the evaluation of any symbolic
+// links.
+// The original implementation can be referenced to filepath.EvalSymlinks,
+// but it will return the current path other then ENOENT error while walkSymlinks.
+// If path is relative the result will be relative to the current directory,
+// unless one of the components is an absolute symbolic link.
+// EvalSymlinks calls Clean on the result.
+func evalSymlinks(path string) (string, error) {
+	return evalSymlink(path)
+}

eval_symlink_test.go

@@ -0,0 +1,61 @@
+package fs
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEvalSymlinks(t *testing.T) {
+	tmpDir := t.TempDir()
+	t.Log(tmpDir)
+	cases := []struct {
+		name        string
+		path        string
+		lpath       string
+		target      string
+		targetExist bool
+		expected    string
+	}{
+		{"symlink point to an existing target", filepath.Join(tmpDir, "lna"), "", filepath.Join(tmpDir, "a"), true, filepath.Join(tmpDir, "a")},
+		{"symlink point to an non-existent target", filepath.Join(tmpDir, "lnb"), "", filepath.Join(tmpDir, "b"), false, filepath.Join(tmpDir, "b")},
+		{"symlink point to another symlink", filepath.Join(tmpDir, "lnd"), filepath.Join(tmpDir, "lnc"), filepath.Join(tmpDir, "c"), false, filepath.Join(tmpDir, "c")},
+		{"symlink point to an relative target", filepath.Join(tmpDir, "lle"), "", tmpDir + "/./e", false, filepath.Join(tmpDir, "e")},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.targetExist {
+				err := os.MkdirAll(tt.target, 0755)
+				if err != nil {
+					t.Log(err.Error())
+				}
+			}
+
+			if tt.lpath != "" {
+				err := os.Symlink(tt.target, tt.lpath)
+				if err != nil {
+					t.Log(err.Error())
+				}
+				err = os.Symlink(tt.lpath, tt.path)
+				if err != nil {
+					t.Log(err.Error())
+				}
+			} else {
+				err := os.Symlink(tt.target, tt.path)
+				if err != nil {
+					t.Log(err.Error())
+				}
+			}
+
+			actualTarget, err := evalSymlinks(tt.path)
+			if err != nil {
+				t.Log(err.Error())
+			}
+
+			assert.Equal(t, tt.expected, actualTarget)
+		})
+	}
+}

go.mod

@@ -3,7 +3,7 @@ module github.com/beyondstorage/go-service-fs/v3
 go 1.15
 
 require (
-	github.com/beyondstorage/go-integration-test/v4 v4.2.1-0.20210728064741-17203b58d96c
+	github.com/beyondstorage/go-integration-test/v4 v4.3.0
 	github.com/beyondstorage/go-storage/v4 v4.4.1-0.20210730075750-6e541b87ea46
 	github.com/qingstor/go-mime v0.1.0
 	github.com/stretchr/testify v1.7.0

go.sum

@@ -1,7 +1,7 @@
 github.com/Xuanwo/templateutils v0.1.0 h1:WpkWOqQtIQ2vAIpJLa727DdN8WtxhUkkbDGa6UhntJY=
 github.com/Xuanwo/templateutils v0.1.0/go.mod h1:OdE0DJ+CJxDBq6psX5DPV+gOZi8bhuHuVUpPCG++Wb8=
-github.com/beyondstorage/go-integration-test/v4 v4.2.1-0.20210728064741-17203b58d96c h1:bYh9zp/ZFg6fLdAL2vpO+JMX8aOCWQzA4jEeG4OZr1w=
-github.com/beyondstorage/go-integration-test/v4 v4.2.1-0.20210728064741-17203b58d96c/go.mod h1:HKgzemQZpxoHBL49JYEUnLTb5eteUhzcvmmPL7EDT/Y=
+github.com/beyondstorage/go-integration-test/v4 v4.3.0 h1:WZ95f78RKlHpvft8zHcMaoa2aaTF/jzlzINhMD0EMHY=
+github.com/beyondstorage/go-integration-test/v4 v4.3.0/go.mod h1:HKgzemQZpxoHBL49JYEUnLTb5eteUhzcvmmPL7EDT/Y=
 github.com/beyondstorage/go-storage/v4 v4.4.0/go.mod h1:mc9VzBImjXDg1/1sLfta2MJH79elfM6m47ZZvZ+q/Uw=
 github.com/beyondstorage/go-storage/v4 v4.4.1-0.20210730075750-6e541b87ea46 h1:sUmtn3cWgpjetIv/lSzZ6AA9GnzvxPjalTvRY1ZDzOg=
 github.com/beyondstorage/go-storage/v4 v4.4.1-0.20210730075750-6e541b87ea46/go.mod h1:mc9VzBImjXDg1/1sLfta2MJH79elfM6m47ZZvZ+q/Uw=

storage.go

@@ -336,9 +336,7 @@ func (s *Storage) stat(ctx context.Context, path string, opt pairStorageStat) (o
 	if fi.Mode()&os.ModeSymlink != 0 {
 		o.Mode |= ModeLink
 
-		// FIXME: `filepath.EvalSymlinks(rp)` can't get the target exactly when target is not a exists file,
-		// so we have temporarily used os.ReadLink instead.
-		target, err := os.Readlink(rp)
+		target, err := evalSymlinks(rp)
 		if err != nil {
 			return nil, err
 		}

symlink.go

@@ -0,0 +1,189 @@
+package fs
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"runtime"
+	"syscall"
+)
+
+func isSlash(c uint8) bool {
+	return c == '\\' || c == '/'
+}
+
+func volumeNameLen(path string) int {
+	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
+}
+
+func walkSymlinks(path string) (string, error) {
+	volLen := volumeNameLen(path)
+	pathSeparator := string(os.PathSeparator)
+
+	if volLen < len(path) && os.IsPathSeparator(path[volLen]) {
+		volLen++
+	}
+	vol := path[:volLen]
+	dest := vol
+	linksWalked := 0
+	var i = 0
+	for start, end := volLen, volLen; start < len(path); start = end {
+		for start < len(path) && os.IsPathSeparator(path[start]) {
+			start++
+		}
+		end = start
+		for end < len(path) && !os.IsPathSeparator(path[end]) {
+			end++
+		}
+
+		// On Windows, "." can be a symlink.
+		// We look it up, and use the value if it is absolute.
+		// If not, we just return ".".
+		isWindowsDot := runtime.GOOS == "windows" && path[volumeNameLen(path):] == "."
+
+		// The next path component is in path[start:end].
+		if end == start {
+			// No more path components.
+			break
+		} else if path[start:end] == "." && !isWindowsDot {
+			// Ignore path component ".".
+			continue
+		} else if path[start:end] == ".." {
+			// Back up to previous component if possible.
+			// Note that volLen includes any leading slash.
+
+			// Set r to the index of the last slash in dest,
+			// after the volume.
+			var r int
+			for r = len(dest) - 1; r >= volLen; r-- {
+				if os.IsPathSeparator(dest[r]) {
+					break
+				}
+			}
+			if r < volLen || dest[r+1:] == ".." {
+				// Either path has no slashes
+				// (it's empty or just "C:")
+				// or it ends in a ".." we had to keep.
+				// Either way, keep this "..".
+				if len(dest) > volLen {
+					dest += pathSeparator
+				}
+				dest += ".."
+			} else {
+				// Discard everything since the last slash.
+				dest = dest[:r]
+			}
+			continue
+		}
+
+		// Ordinary path component. Add it to result.
+
+		if len(dest) > volumeNameLen(dest) && !os.IsPathSeparator(dest[len(dest)-1]) {
+			dest += pathSeparator
+		}
+
+		dest += path[start:end]
+
+		// Resolve symlink.
+
+		i++
+
+		fi, err := os.Lstat(dest)
+		if err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				return filepath.Clean(dest + path[end:]), nil
+			}
+			return "", err
+		}
+
+		if fi.Mode()&os.ModeSymlink == 0 {
+			if !fi.Mode().IsDir() && end < len(path) {
+				return "", syscall.ENOTDIR
+			}
+			continue
+		}
+
+		// Found symlink.
+
+		linksWalked++
+		if linksWalked > 255 {
+			return "", errors.New("EvalSymlinks: too many links")
+		}
+
+		link, err := os.Readlink(dest)
+		if err != nil {
+			return "", err
+		}
+
+		if isWindowsDot && !filepath.IsAbs(link) {
+			// On Windows, if "." is a relative symlink,
+			// just return ".".
+			break
+		}
+
+		path = link + path[end:]
+
+		v := volumeNameLen(link)
+		if v > 0 {
+			// Symlink to drive name is an absolute path.
+			if v < len(link) && os.IsPathSeparator(link[v]) {
+				v++
+			}
+			vol = link[:v]
+			dest = vol
+			end = len(vol)
+		} else if len(link) > 0 && os.IsPathSeparator(link[0]) {
+			// Symlink to absolute path.
+			dest = link[:1]
+			end = 1
+		} else {
+			// Symlink to relative path; replace last
+			// path component in dest.
+			var r int
+			for r = len(dest) - 1; r >= volLen; r-- {
+				if os.IsPathSeparator(dest[r]) {
+					break
+				}
+			}
+			if r < volLen {
+				dest = vol
+			} else {
+				dest = dest[:r]
+			}
+			end = 0
+		}
+	}
+	return filepath.Clean(dest), nil
+}

symlink_unix.go

@@ -0,0 +1,7 @@
+// +build !windows
+
+package fs
+
+func evalSymlink(path string) (string, error) {
+	return walkSymlinks(path)
+}