fix(overlay): stabilize explicitly tagged folded scalars and strengthen tests

Author: AshGodfrey

overlay/foldedscalar.go

@@ -26,8 +26,8 @@ func stabilizeFoldedScalars(node *yaml.Node) {
 		return
 	}
 
-	if node.Kind == yaml.ScalarNode && node.Style == yaml.FoldedStyle && hasMoreIndentedLine(node.Value) {
-		node.Style = yaml.LiteralStyle
+	if node.Kind == yaml.ScalarNode && node.Style&yaml.FoldedStyle != 0 && hasMoreIndentedLine(node.Value) {
+		node.Style = node.Style&^yaml.FoldedStyle | yaml.LiteralStyle
 	}
 
 	for _, child := range node.Content {

overlay/foldedscalar_test.go

@@ -79,6 +79,50 @@ func TestApplyToSurvivesRepeatedApplies(t *testing.T) {
 	}
 }
 
+func TestApplyToStrictSurvivesRepeatedApplies(t *testing.T) {
+	t.Parallel()
+
+	o := &Overlay{
+		Version: "1.0.0",
+		Info:    Info{Title: "Test", Version: "1.0.0"},
+		Actions: []Action{
+			{
+				Target: "$.title",
+				Update: yaml.Node{Kind: yaml.ScalarNode, Tag: "!!str", Value: "Updated"},
+			},
+		},
+	}
+
+	doc := "title: Original\n" + foldedWithMoreIndentedLine
+	want := decodeDescription(t, doc)
+
+	for i := range 30 {
+		var node yaml.Node
+		require.NoError(t, yaml.Unmarshal([]byte(doc), &node))
+		_, err := o.ApplyToStrict(&node)
+		require.NoError(t, err)
+
+		out, err := yaml.Marshal(&node)
+		require.NoError(t, err)
+
+		doc = string(out)
+		assert.Equal(t, want, decodeDescription(t, doc), "value changed after %d applies", i+1)
+	}
+}
+
+func TestStabilizeFoldedScalarsHandlesExplicitTags(t *testing.T) {
+	t.Parallel()
+
+	doc := "description: !!str >-\n  a\n   b\n"
+	want := decodeDescription(t, doc)
+
+	for i := range 5 {
+		doc = roundTrip(t, doc, true)
+		assert.Equal(t, want, decodeDescription(t, doc), "value changed after %d round trips", i+1)
+	}
+	assert.Contains(t, doc, "!!str", "explicit tag should be preserved")
+}
+
 func TestStabilizeFoldedScalarsSurvivesRepeatedRoundTrips(t *testing.T) {
 	t.Parallel()
 
@@ -105,16 +149,19 @@ func TestStabilizeFoldedScalarsLeavesStableStylesAlone(t *testing.T) {
 	t.Parallel()
 
 	tests := []struct {
-		name string
-		doc  string
+		name  string
+		doc   string
+		style string
 	}{
 		{
-			name: "folded scalar with no more-indented line",
-			doc:  "description: >-\n  one line\n  another line\n",
+			name:  "folded scalar with no more-indented line",
+			doc:   "description: >-\n  one line\n  another line\n",
+			style: ">-",
 		},
 		{
-			name: "literal scalar with more-indented line",
-			doc:  "description: |-\n  one line\n   more indented\n",
+			name:  "literal scalar with more-indented line",
+			doc:   "description: |-\n  one line\n   more indented\n",
+			style: "|-",
 		},
 		{
 			name: "plain scalar",
@@ -128,10 +175,17 @@ func TestStabilizeFoldedScalarsLeavesStableStylesAlone(t *testing.T) {
 
 			want := decodeDescription(t, tt.doc)
 
-			doc := tt.doc
+			doc := roundTrip(t, tt.doc, true)
+			assert.Equal(t, want, decodeDescription(t, doc))
+			if tt.style != "" {
+				assert.Contains(t, doc, tt.style, "original style should be preserved")
+			}
+
 			for range 5 {
-				doc = roundTrip(t, doc, true)
-				assert.Equal(t, want, decodeDescription(t, doc))
+				next := roundTrip(t, doc, true)
+				assert.Equal(t, doc, next, "representation should be a fixed point")
+				assert.Equal(t, want, decodeDescription(t, next))
+				doc = next
 			}
 		})
 	}