walker: add callback to inform about leaving a directory

internal/dump/common.go

@@ -70,7 +70,7 @@ func sendNodes(ctx context.Context, repo restic.Repository, root *restic.Node, c
 		return nil
 	}
 
-	err := walker.Walk(ctx, repo, *root.Subtree, func(_ restic.ID, nodepath string, node *restic.Node, err error) error {
+	err := walker.Walk(ctx, repo, *root.Subtree, walker.WalkVisitor{ProcessNode: func(_ restic.ID, nodepath string, node *restic.Node, err error) error {
 		if err != nil {
 			return err
 		}
@@ -91,7 +91,7 @@ func sendNodes(ctx context.Context, repo restic.Repository, root *restic.Node, c
 		}
 
 		return nil
-	})
+	}})
 
 	return err
 }

internal/walker/walker.go

@@ -23,12 +23,20 @@ var ErrSkipNode = errors.New("skip this node")
 // tree are skipped.
 type WalkFunc func(parentTreeID restic.ID, path string, node *restic.Node, nodeErr error) (err error)
 
+type WalkVisitor struct {
+	// If the node is a `dir`, it will be entered afterwards unless `ErrSkipNode`
+	// was returned. This function is mandatory
+	ProcessNode WalkFunc
+	// Optional callback
+	LeaveDir func(path string)
+}
+
 // Walk calls walkFn recursively for each node in root. If walkFn returns an
 // error, it is passed up the call stack. The trees in ignoreTrees are not
 // walked. If walkFn ignores trees, these are added to the set.
-func Walk(ctx context.Context, repo restic.BlobLoader, root restic.ID, walkFn WalkFunc) error {
+func Walk(ctx context.Context, repo restic.BlobLoader, root restic.ID, visitor WalkVisitor) error {
 	tree, err := restic.LoadTree(ctx, repo, root)
-	err = walkFn(root, "/", nil, err)
+	err = visitor.ProcessNode(root, "/", nil, err)
 
 	if err != nil {
 		if err == ErrSkipNode {
@@ -37,13 +45,13 @@ func Walk(ctx context.Context, repo restic.BlobLoader, root restic.ID, walkFn Wa
 		return err
 	}
 
-	return walk(ctx, repo, "/", root, tree, walkFn)
+	return walk(ctx, repo, "/", root, tree, visitor)
 }
 
 // walk recursively traverses the tree, ignoring subtrees when the ID of the
 // subtree is in ignoreTrees. If err is nil and ignore is true, the subtree ID
 // will be added to ignoreTrees by walk.
-func walk(ctx context.Context, repo restic.BlobLoader, prefix string, parentTreeID restic.ID, tree *restic.Tree, walkFn WalkFunc) (err error) {
+func walk(ctx context.Context, repo restic.BlobLoader, prefix string, parentTreeID restic.ID, tree *restic.Tree, visitor WalkVisitor) (err error) {
 	sort.Slice(tree.Nodes, func(i, j int) bool {
 		return tree.Nodes[i].Name < tree.Nodes[j].Name
 	})
@@ -56,7 +64,7 @@ func walk(ctx context.Context, repo restic.BlobLoader, prefix string, parentTree
 		}
 
 		if node.Type != "dir" {
-			err := walkFn(parentTreeID, p, node, nil)
+			err := visitor.ProcessNode(parentTreeID, p, node, nil)
 			if err != nil {
 				if err == ErrSkipNode {
 					// skip the remaining entries in this tree
@@ -74,18 +82,22 @@ func walk(ctx context.Context, repo restic.BlobLoader, prefix string, parentTree
 		}
 
 		subtree, err := restic.LoadTree(ctx, repo, *node.Subtree)
-		err = walkFn(parentTreeID, p, node, err)
+		err = visitor.ProcessNode(parentTreeID, p, node, err)
 		if err != nil {
 			if err == ErrSkipNode {
 				continue
 			}
 		}
 
-		err = walk(ctx, repo, p, *node.Subtree, subtree, walkFn)
+		err = walk(ctx, repo, p, *node.Subtree, subtree, visitor)
 		if err != nil {
 			return err
 		}
 	}
 
+	if visitor.LeaveDir != nil {
+		visitor.LeaveDir(prefix)
+	}
+
 	return nil
 }

internal/walker/walker_test.go

@@ -406,7 +406,7 @@ func TestWalker(t *testing.T) {
 					defer cancel()
 
 					fn, last := check(t)
-					err := Walk(ctx, repo, root, fn)
+					err := Walk(ctx, repo, root, WalkVisitor{ProcessNode: fn})
 					if err != nil {
 						t.Error(err)
 					}