Move code to walk with symlinks to the utils module

tools/utils/paths.go

@@ -3,6 +3,7 @@
 package utils
 
 import (
+	"io/fs"
 	"os"
 	"os/user"
 	"path/filepath"
@@ -87,3 +88,78 @@ func ConfigDir() string {
 
 	return config_dir
 }
+
+type Walk_callback func(path, abspath string, d fs.DirEntry, err error) error
+
+func transform_symlink(path string) string {
+	if q, err := filepath.EvalSymlinks(path); err == nil {
+		return q
+	}
+	return path
+}
+
+func needs_symlink_recurse(path string, d fs.DirEntry) bool {
+	if d.Type()&os.ModeSymlink == os.ModeSymlink {
+		if s, serr := os.Stat(path); serr == nil && s.IsDir() {
+			return true
+		}
+	}
+	return false
+}
+
+type transformed_walker struct {
+	seen               map[string]bool
+	real_callback      Walk_callback
+	transform_func     func(string) string
+	needs_recurse_func func(string, fs.DirEntry) bool
+}
+
+var sep = string(os.PathSeparator)
+
+func (self *transformed_walker) walk(dirpath string) error {
+	resolved_path := self.transform_func(dirpath)
+	if self.seen[resolved_path] {
+		return nil
+	}
+	self.seen[resolved_path] = true
+
+	c := func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			// Happens if ReadDir on d failed, skip it in that case
+			return fs.SkipDir
+		}
+		rpath, err := filepath.Rel(resolved_path, path)
+		if err != nil {
+			return err
+		}
+		// we cant use filepath.Join here as it calls Clean() which can alter dirpath if it contains .. or . etc.
+		path_based_on_original_dir := dirpath
+		if !strings.HasSuffix(dirpath, sep) {
+			path_based_on_original_dir += sep
+		}
+		path_based_on_original_dir += rpath
+		if self.needs_recurse_func(path, d) {
+			err = self.walk(path_based_on_original_dir)
+		} else {
+			err = self.real_callback(path_based_on_original_dir, path, d, err)
+		}
+		return err
+	}
+
+	return filepath.WalkDir(resolved_path, c)
+}
+
+// Walk, recursing into symlinks that point to directories. Ignores directories
+// that could not be read.
+func WalkWithSymlink(dirpath string, callback Walk_callback, transformers ...func(string) string) error {
+
+	transform := func(path string) string {
+		for _, t := range transformers {
+			path = t(path)
+		}
+		return transform_symlink(path)
+	}
+	sw := transformed_walker{
+		seen: make(map[string]bool), real_callback: callback, transform_func: transform, needs_recurse_func: needs_symlink_recurse}
+	return sw.walk(dirpath)
+}