lib/fs: Evaluate root when watching not on fs creation (fixes #5043) (#5105)

lib/fs/basicfs.go

@@ -25,8 +25,7 @@ var (
 // The BasicFilesystem implements all aspects by delegating to package os.
 // All paths are relative to the root and cannot (should not) escape the root directory.
 type BasicFilesystem struct {
-	root                 string
-	rootSymlinkEvaluated string
+	root string
 }
 
 func newBasicFilesystem(root string) *BasicFilesystem {
@@ -36,7 +35,8 @@ func newBasicFilesystem(root string) *BasicFilesystem {
 	// C:\somedir\ ->  C:\somedir\\   ->  C:\somedir
 	// This way in the tests, we get away without OS specific separators
 	// in the test configs.
-	root = filepath.Dir(root + string(filepath.Separator))
+	sep := string(filepath.Separator)
+	root = filepath.Dir(root + sep)
 
 	// Attempt tilde expansion; leave unchanged in case of error
 	if path, err := ExpandTilde(root); err == nil {
@@ -53,34 +53,17 @@ func newBasicFilesystem(root string) *BasicFilesystem {
 		}
 	}
 
-	rootSymlinkEvaluated, err := filepath.EvalSymlinks(root)
-	if err != nil {
-		rootSymlinkEvaluated = root
-	}
-
-	return &BasicFilesystem{
-		root:                 adjustRoot(root),
-		rootSymlinkEvaluated: adjustRoot(rootSymlinkEvaluated),
-	}
-}
-
-func adjustRoot(root string) string {
 	// Attempt to enable long filename support on Windows. We may still not
 	// have an absolute path here if the previous steps failed.
 	if runtime.GOOS == "windows" {
-		if filepath.IsAbs(root) && !strings.HasPrefix(root, `\\`) {
-			root = `\\?\` + root
-		}
-		return root
+		root = longFilenameSupport(root)
+	} else if !strings.HasSuffix(root, sep) {
+		// If we're not on Windows, we want the path to end with a slash to
+		// penetrate symlinks. On Windows, paths must not end with a slash.
+		root = root + sep
 	}
 
-	// If we're not on Windows, we want the path to end with a slash to
-	// penetrate symlinks. On Windows, paths must not end with a slash.
-	if root[len(root)-1] != filepath.Separator {
-		root = root + string(filepath.Separator)
-	}
-
-	return root
+	return &BasicFilesystem{root}
 }
 
 // rooted expands the relative path to the full path that is then used with os
@@ -91,14 +74,6 @@ func (f *BasicFilesystem) rooted(rel string) (string, error) {
 	return rooted(rel, f.root)
 }
 
-// rootedSymlinkEvaluated does the same as rooted, but the returned path will not
-// contain any symlinks.  package. If the relative path somehow causes the final
-// path to escape the root directory, this returns an error, to prevent accessing
-// files that are not in the shared directory.
-func (f *BasicFilesystem) rootedSymlinkEvaluated(rel string) (string, error) {
-	return rooted(rel, f.rootSymlinkEvaluated)
-}
-
 func rooted(rel, root string) (string, error) {
 	// The root must not be empty.
 	if root == "" {
@@ -138,10 +113,6 @@ func (f *BasicFilesystem) unrooted(path string) string {
 	return rel(path, f.root)
 }
 
-func (f *BasicFilesystem) unrootedSymlinkEvaluated(path string) string {
-	return rel(path, f.rootSymlinkEvaluated)
-}
-
 func rel(path, prefix string) string {
 	return strings.TrimPrefix(strings.TrimPrefix(path, prefix), string(PathSeparator))
 }
@@ -372,3 +343,13 @@ func (e fsFileInfo) IsRegular() bool {
 	// Must use fsFileInfo.Mode() because it may apply magic.
 	return e.Mode()&ModeType == 0
 }
+
+// longFilenameSupport adds the necessary prefix to the path to enable long
+// filename support on windows if necessary.
+// This does NOT check the current system, i.e. will also take effect on unix paths.
+func longFilenameSupport(path string) string {
+	if filepath.IsAbs(path) && !strings.HasPrefix(path, `\\`) {
+		return `\\?\` + path
+	}
+	return path
+}