groot/riofs: provide a stable top-dir to Walk

Signed-off-by: Sebastien Binet <binet@cern.ch>

groot/rcmd/merge.go

@@ -109,12 +109,15 @@ func (cmd *mergeCmd) mergeTasksFrom(o *riofs.File, fname string) ([]task, error)
 	}
 	defer f.Close()
 
+	// handle relative/absolute path
+	top := stdpath.Join(f.Name(), ".")
+
 	var tsks []task
 	err = riofs.Walk(f, func(path string, obj root.Object, err error) error {
 		if err != nil {
 			return err
 		}
-		name := path[len(f.Name()):]
+		name := path[len(top):]
 		if name == "" {
 			return nil
 		}

groot/riofs/walk.go

@@ -23,7 +23,20 @@ var SkipDir = errors.New("riofs: skip this directory") //lint:ignore ST1012 EOF-
 //
 // If an object exists with multiple cycle values, only the latest one is considered.
 func Walk(dir Directory, walkFn WalkFunc) error {
-	err := walk(dir.(root.Named).Name(), dir.(root.Object), walkFn)
+	// prepare a "stable" top directory.
+	// depending on whether the dir is rooted in a file that was created
+	// with an absolute path, the call to Name() may return a path like:
+	//   ./data/file.root
+	// the first call to walkFn will be given "./data/file.root" as a 'path'
+	// argument.
+	// but the subsequent calls (walking through directories' hierarchy) will
+	// be given "data/file.root/dir11", instead of the probably expected
+	// "./data/file.root/dir11".
+	//
+	// side-step this by providing directly the "stable" top directory in a
+	// more regularized form.
+	top := stdpath.Join(dir.(root.Named).Name(), ".")
+	err := walk(top, dir.(root.Object), walkFn)
 	if err == SkipDir {
 		return nil
 	}

groot/riofs/walk_test.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"go-hep.org/x/hep/groot/rbase"
 	"go-hep.org/x/hep/groot/rhist"
 	"go-hep.org/x/hep/groot/root"
@@ -403,6 +404,85 @@ func TestFileOf(t *testing.T) {
 	}
 }
 
+func TestWalk(t *testing.T) {
+	tmp, err := os.MkdirTemp("", "groot-riofs-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmp)
+
+	err = os.MkdirAll(stdpath.Join(tmp, "data"), 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("could not get working directory: %+v", err)
+	}
+	defer os.Chdir(pwd)
+
+	err = os.Chdir(tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fname := "./data/file.root"
+
+	f, err := Create(fname)
+	if err != nil {
+		t.Fatalf("could not create ROOT file: %+v", err)
+	}
+	defer f.Close()
+
+	err = os.Chdir(pwd)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rd := Dir(f)
+
+	display := func() string {
+		o := new(strings.Builder)
+		err := Walk(f, func(path string, obj root.Object, err error) error {
+			fmt.Fprintf(o, "%s (%s)\n", path, obj.Class())
+			return nil
+		})
+		if err != nil {
+			return fmt.Errorf("could not display file content: %w", err).Error()
+		}
+		return o.String()
+	}
+
+	for _, name := range []string{
+		"dir1/dir11/dir111",
+		"dir1/dir12/dir121",
+		"dir2/dir21",
+		"dir2/dir22",
+	} {
+		_, err = rd.Mkdir(name)
+		if err != nil {
+			t.Fatalf("could not create dir %q: %+v", name, err)
+		}
+	}
+
+	got := display()
+	want := `data/file.root (TFile)
+data/file.root/dir1 (TDirectoryFile)
+data/file.root/dir1/dir11 (TDirectoryFile)
+data/file.root/dir1/dir11/dir111 (TDirectoryFile)
+data/file.root/dir1/dir12 (TDirectoryFile)
+data/file.root/dir1/dir12/dir121 (TDirectoryFile)
+data/file.root/dir2 (TDirectoryFile)
+data/file.root/dir2/dir21 (TDirectoryFile)
+data/file.root/dir2/dir22 (TDirectoryFile)
+`
+	if got != want {
+		diff := cmp.Diff(want, got)
+		t.Fatalf("invalid Walk display: -- (-ref +got)\n%s", diff)
+	}
+}
+
 type unknownDirImpl struct{}
 
 func (dir *unknownDirImpl) Get(namecycle string) (root.Object, error) { panic("not implemented") }