test(tag): handle nil tags in slices and getters

Author: linkdata

element_test.go

@@ -84,6 +84,10 @@ func (a testApplyGetterAll) JawsInit(elem *Element) error {
 	return a.initErr
 }
 
+type testNilTagGetter struct{}
+
+func (testNilTagGetter) JawsGetTag(tag.Context) any { return nil }
+
 func TestElement_helpers(t *testing.T) {
 	is := newTestHelper(t)
 	rq := newTestRequest(t)
@@ -501,6 +505,31 @@ func TestElement_ApplyGetter_NonComparableHandler(t *testing.T) {
 	}
 }
 
+func TestElement_ApplyGetter_NilTagGetter(t *testing.T) {
+	rq := newTestRequest(t)
+	defer rq.Close()
+
+	e := rq.NewElement(&testUi{s: "foo"})
+	gotTag, attrs, err := e.ApplyGetter(testNilTagGetter{})
+	if gotTag != nil {
+		t.Fatalf("expected nil tag, got %#v", gotTag)
+	}
+	if len(attrs) != 0 {
+		t.Fatalf("expected no attrs, got %#v", attrs)
+	}
+	if err != nil {
+		t.Fatalf("ApplyGetter returned error: %v", err)
+	}
+	if got := rq.TagsOf(e); len(got) != 0 {
+		t.Fatalf("expected nil tag getter to not tag element, got %v", got)
+	}
+
+	e.Tag(nil)
+	if got := rq.TagsOf(e); len(got) != 0 {
+		t.Fatalf("expected explicit nil tag to be ignored, got %v", got)
+	}
+}
+
 func TestElement_ApplyParams_NonComparableHandler(t *testing.T) {
 	rq := newTestRequest(t)
 	defer rq.Close()

lib/tag/tag.go

@@ -102,6 +102,15 @@ func addActiveTags(result []any, active []any) ([]any, error) {
 	return result, nil
 }
 
+func hasNonNilTag(tags []any) bool {
+	for _, tag := range tags {
+		if tag != nil {
+			return true
+		}
+	}
+	return false
+}
+
 func expand(depth int, ctx Context, tag any, result []any, active []any) ([]any, error) {
 	if depth > 10 || len(result) > 100 {
 		return result, ErrTooManyTags
@@ -128,6 +137,9 @@ func expand(depth int, ctx Context, tag any, result []any, active []any) ([]any,
 		}
 		return expand(depth+1, ctx, data.JawsGetTag(ctx), result, append(active, data))
 	case []any:
+		if !hasNonNilTag(data) {
+			return result, nil
+		}
 		if idx := findActiveIndex(active, data); idx >= 0 {
 			return addActiveTags(result, active[idx:])
 		}

lib/tag/tag_test.go

@@ -132,6 +132,11 @@ func TestTagExpand(t *testing.T) {
 			tag:  []any{Tag("a"), &av},
 			want: []any{Tag("a"), &av},
 		},
+		{
+			name: "[]any nils",
+			tag:  []any{nil, nil},
+			want: nil,
+		},
 		{
 			name: "error",
 			tag:  boom,