Fix resolving links in sharded directories on gateway

path/resolver/resolver.go

@@ -69,25 +69,46 @@ func (r *Resolver) ResolveToLastNode(ctx context.Context, fpath path.Path) (ipld
 	}
 
 	for len(p) > 0 {
-		val, rest, err := nd.Resolve(p)
+		lnk, rest, err := r.ResolveOnce(ctx, r.DAG, nd, p)
+
+		// Note: have to drop the error here as `ResolveOnce` doesn't handle 'leaf'
+		// paths (so e.g. for `echo '{"foo":123}' | ipfs dag put` we wouldn't be
+		// able to resolve `zdpu[...]/foo`)
+		if lnk == nil {
+			break
+		}
+
 		if err != nil {
 			return nil, nil, err
 		}
 
-		switch val := val.(type) {
-		case *ipld.Link:
-			next, err := val.GetNode(ctx, r.DAG)
-			if err != nil {
-				return nil, nil, err
-			}
-			nd = next
-			p = rest
-		default:
-			return nd, p, nil
+		next, err := lnk.GetNode(ctx, r.DAG)
+		if err != nil {
+			return nil, nil, err
 		}
+		nd = next
+		p = rest
+	}
+
+	if len(p) == 0 {
+		return nd, nil, nil
 	}
 
-	return nd, nil, nil
+	// Confirm the path exists within the object
+	val, rest, err := nd.Resolve(p)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if len(rest) > 0 {
+		return nil, nil, errors.New("path failed to resolve fully")
+	}
+	switch val.(type) {
+	case *ipld.Link:
+		return nil, nil, errors.New("inconsistent ResolveOnce / nd.Resolve")
+	default:
+		return nd, p, nil
+	}
 }
 
 // ResolvePath fetches the node for given path. It returns the last item

test/sharness/t0260-sharding.sh

@@ -76,6 +76,15 @@ test_expect_success "'ipfs ls --resolve-type=false' admits missing block" '
   test_cmp sharded_out missing_out
 '
 
+test_launch_ipfs_daemon
+
+test_expect_success "gateway can resolve sharded dirs" '
+  echo 100 > expected &&
+  curl -sfo actual "http://127.0.0.1:$GWAY_PORT/ipfs/$SHARDED/file100" &&
+  test_cmp expected actual
+'
+
+test_kill_ipfs_daemon
 
 test_add_large_dir_v1() {
   exphash="$1"