fix: overwrite attribute values when not mergeable

merger/merger.go

@@ -108,11 +108,22 @@ const UnstableInsertIndexKey = "_gazelle_insert_index"
 // be modified.
 func MergeFile(oldFile *rule.File, emptyRules, genRules []*rule.Rule, phase Phase, kinds map[string]rule.KindInfo, aliasedKinds map[string]string) {
 	getMergeAttrs := func(r *rule.Rule) map[string]bool {
-		if phase == PreResolve {
-			return kinds[r.Kind()].MergeableAttrs
-		} else {
-			return kinds[r.Kind()].ResolveAttrs
+		kind := kinds[r.Kind()]
+
+		mergeableAttrs := map[string]bool{
+			// Name and visibility are uniquely managed by gazelle.
+			"name":       false,
+			"visibility": false,
 		}
+
+		// All attributes managed by gazelle, marking only the current merge attributes
+		// with a truthy value.
+		combineMergeAttrs(mergeableAttrs, kind.MergeableAttrs, phase == PreResolve)
+		combineMergeAttrs(mergeableAttrs, kind.ResolveAttrs, phase == PostResolve)
+		combineMergeAttrs(mergeableAttrs, kind.NonEmptyAttrs, false)
+		combineMergeAttrs(mergeableAttrs, kind.SubstituteAttrs, false)
+
+		return mergeableAttrs
 	}
 
 	// Merge empty rules into the file and delete any rules which become empty.
@@ -174,6 +185,12 @@ func MergeFile(oldFile *rule.File, emptyRules, genRules []*rule.Rule, phase Phas
 	}
 }
 
+func combineMergeAttrs(dst map[string]bool, src map[string]bool, value bool) {
+	for k, _ := range src {
+		dst[k] = value || dst[k]
+	}
+}
+
 // substituteRule replaces local labels (those beginning with ":", referring to
 // targets in the same package) according to a substitution map. This is used
 // to update generated rules before merging when the corresponding existing

rule/merge.go

@@ -41,6 +41,10 @@ import (
 // marked with a "# keep" comment, values in the attribute not marked with
 // a "# keep" comment will be dropped. If the attribute is empty afterward,
 // it will be deleted.
+//
+// If src has an attribute not present in 'mergeable' and the attribute
+// does not exist or is not marked with a "# keep" comment, values in the
+// dst attribute will be overwritten.
 func MergeRules(src, dst *Rule, mergeable map[string]bool, filename string) {
 	if dst.ShouldKeep() {
 		return
@@ -63,9 +67,20 @@ func MergeRules(src, dst *Rule, mergeable map[string]bool, filename string) {
 
 	// Merge attributes from src into dst.
 	for key, srcAttr := range src.attrs {
-		if dstAttr, ok := dst.attrs[key]; !ok {
+		// Always set properties that are not yet set.
+		dstAttr, dstAttrExists := dst.attrs[key]
+		if !dstAttrExists {
 			dst.SetAttr(key, srcAttr.expr.RHS)
-		} else if mergeable[key] && !ShouldKeep(dstAttr.expr) {
+			continue
+		}
+
+		// Do not overwrite attributes marked with "# keep".
+		if ShouldKeep(dstAttr.expr) {
+			continue
+		}
+
+		if attrMergeable, attrKnown := mergeable[key]; attrMergeable {
+			// Merge mergeable attributes.
 			if mergedValue, err := mergeAttrValues(&srcAttr, &dstAttr); err != nil {
 				start, end := dstAttr.expr.RHS.Span()
 				log.Printf("%s:%d.%d-%d.%d: could not merge expression", filename, start.Line, start.LineRune, end.Line, end.LineRune)
@@ -74,6 +89,9 @@ func MergeRules(src, dst *Rule, mergeable map[string]bool, filename string) {
 			} else {
 				dst.SetAttr(key, mergedValue)
 			}
+		} else if !attrKnown {
+			// Overwrite unknown attributes.
+			dst.SetAttr(key, srcAttr.expr.RHS)
 		}
 	}
 

rule/merge_test.go

@@ -16,6 +16,7 @@ limitations under the License.
 package rule_test
 
 import (
+	"reflect"
 	"testing"
 
 	"github.com/bazelbuild/bazel-gazelle/rule"
@@ -44,7 +45,7 @@ func TestMergeRules_WithSortedStringAttr(t *testing.T) {
 		sortedStringAttrVal := rule.SortedStrings{"@qux", "//foo:bar", "//foo:baz"}
 		src.SetAttr(sortedStringAttrKey, sortedStringAttrVal)
 		dst := rule.NewRule("go_library", "go_default_library")
-		rule.MergeRules(src, dst, map[string]bool{}, "")
+		rule.MergeRules(src, dst, map[string]bool{"deps": true}, "")
 
 		valExpr, ok := dst.Attr(sortedStringAttrKey).(*bzl.ListExpr)
 		if !ok {
@@ -106,7 +107,7 @@ func TestMergeRules_WithUnsortedStringAttr(t *testing.T) {
 		sortedStringAttrVal := rule.UnsortedStrings{"@qux", "//foo:bar", "//foo:baz"}
 		src.SetAttr(sortedStringAttrKey, sortedStringAttrVal)
 		dst := rule.NewRule("go_library", "go_default_library")
-		rule.MergeRules(src, dst, map[string]bool{}, "")
+		rule.MergeRules(src, dst, map[string]bool{"deps": true}, "")
 
 		valExpr, ok := dst.Attr(sortedStringAttrKey).(*bzl.ListExpr)
 		if !ok {
@@ -147,3 +148,63 @@ func TestMergeRules_WithUnsortedStringAttr(t *testing.T) {
 		}
 	})
 }
+
+func TestMergeRules_WithUnmanagedAttr(t *testing.T) {
+	t.Run("unknown string attributes overwrite attributes in non-empty rule", func(t *testing.T) {
+		src := rule.NewRule("go_library", "go_default_library")
+		unknownStringAttrKey := "unknown_attr"
+		overwrittenAttrVal := rule.UnsortedStrings{"@qux", "//foo:bar", "//foo:baz"}
+		src.SetAttr(unknownStringAttrKey, "foobar")
+		dst := rule.NewRule("go_library", "go_default_library")
+		dst.SetAttr(unknownStringAttrKey, overwrittenAttrVal)
+		rule.MergeRules(src, dst, map[string]bool{}, "")
+
+		valExpr, ok := dst.Attr(unknownStringAttrKey).(*bzl.StringExpr)
+		if !ok {
+			t.Fatalf("unknown attributes (%q) are overwritten: got %v; want *bzl.StringExpr",
+				unknownStringAttrKey, reflect.TypeOf(dst.Attr(unknownStringAttrKey)))
+		}
+
+		expected := "foobar"
+		if valExpr.Value != expected {
+			t.Fatalf("unknown attributes (%q) are overwritten: got %v; want %v",
+				unknownStringAttrKey, valExpr.Value, expected)
+		}
+	})
+
+	t.Run("known string attributes do NOT overwrite attributes in non-empty rule", func(t *testing.T) {
+		src := rule.NewRule("go_library", "go_default_library")
+		unknownStringAttrKey := "unknown_attr"
+		knownStringAttrKey := "knownAttrName"
+		overwrittenAttrVal := "original"
+		src.SetAttr(unknownStringAttrKey, "foobar")
+		src.SetAttr(knownStringAttrKey, "foobar")
+		dst := rule.NewRule("go_library", "go_default_library")
+		dst.SetAttr(unknownStringAttrKey, overwrittenAttrVal)
+		dst.SetAttr(knownStringAttrKey, overwrittenAttrVal)
+		rule.MergeRules(src, dst, map[string]bool{knownStringAttrKey: false}, "")
+
+		// The unknown + overwritten attribute
+		unknownValExpr, ok := dst.Attr(unknownStringAttrKey).(*bzl.StringExpr)
+		if !ok {
+			t.Fatalf("unknown attributes (%q) are overwritten: got %v; want *bzl.StringExpr",
+				unknownStringAttrKey, reflect.TypeOf(dst.Attr(unknownStringAttrKey)))
+		}
+		expected := "foobar"
+		if unknownValExpr.Value != expected {
+			t.Fatalf("unknown attributes (%q) are overwritten: got %v; want %v",
+				unknownStringAttrKey, unknownValExpr.Value, expected)
+		}
+
+		// The known but non-mergeable attributes
+		knownValExpr, ok := dst.Attr(knownStringAttrKey).(*bzl.StringExpr)
+		if !ok {
+			t.Fatalf("known attributes (%q) are NOT overwritten: got %v; want *bzl.StringExpr",
+				knownStringAttrKey, reflect.TypeOf(dst.Attr(knownStringAttrKey)))
+		}
+		if knownValExpr.Value != overwrittenAttrVal {
+			t.Fatalf("known attributes (%q) are NOT overwritten: got %v; want %v",
+				knownStringAttrKey, knownValExpr.Value, overwrittenAttrVal)
+		}
+	})
+}