Fix exclude filter behavior with empty image file (#3819)

Author: doriable

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Add `CSR` category to breaking rules.
 - Add support for local bufplugins for `protoc-gen-buf-breaking` and `protoc-gen-buf-lint`.
 - Add RISC-V (64-bit) binaries for Linux to releases.
+- Fix type filtering on `buf generate` for empty files, files with no declared types.
 
 ## [v1.53.0] - 2025-04-21
 

private/bufpkg/bufimage/bufimageutil/bufimageutil.go

@@ -450,10 +450,9 @@ func (t *transitiveClosure) addElement(
 
 	switch typedDescriptor := descriptor.(type) {
 	case *descriptorpb.FileDescriptorProto:
-		typeNames, ok := imageIndex.FileTypes[typedDescriptor.GetName()]
-		if !ok {
-			return fmt.Errorf("missing %q", typedDescriptor.GetName())
-		}
+		// If the file we are attempting to include is empty (has no types defined), it is still
+		// valid for inclusion.
+		typeNames := imageIndex.FileTypes[typedDescriptor.GetName()]
 		// A file includes all elements. The types are resolved in the image index
 		// to ensure all nested types are included.
 		for _, typeName := range typeNames {

private/bufpkg/bufimage/bufimageutil/bufimageutil_test.go

@@ -504,6 +504,18 @@ func TestDependencies(t *testing.T) {
 	})
 }
 
+func TestEmptyFiles(t *testing.T) {
+	t.Parallel()
+	t.Run("include_empty_file", func(t *testing.T) {
+		t.Parallel()
+		runDiffTest(t, "testdata/empty", "empty.include.txtar", WithIncludeTypes("include"))
+	})
+	t.Run("exclude_empty_file", func(t *testing.T) {
+		t.Parallel()
+		runDiffTest(t, "testdata/empty", "empty.exclude.txtar", WithExcludeTypes("include"))
+	})
+}
+
 func getImage(ctx context.Context, logger *slog.Logger, testdataDir string, options ...bufimage.BuildImageOption) (storage.ReadWriteBucket, bufimage.Image, error) {
 	bucket, err := storageos.NewProvider().NewReadWriteBucket(testdataDir)
 	if err != nil {

private/bufpkg/bufimage/bufimageutil/testdata/empty/a.proto

@@ -0,0 +1,2 @@
+syntax = "proto3";
+package include;

private/bufpkg/bufimage/bufimageutil/testdata/empty/b.proto

@@ -0,0 +1,3 @@
+syntax = "proto3";
+
+import "a.proto";

private/bufpkg/bufimage/bufimageutil/testdata/empty/c.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+package pkg;
+
+import "a.proto";
+
+message Foo {
+  string name = 1;
+}

private/bufpkg/bufimage/bufimageutil/testdata/empty/d.proto

@@ -0,0 +1,4 @@
+syntax = "proto3";
+package pkg;
+
+import "google/protobuf/any.proto";

private/bufpkg/bufimage/bufimageutil/testdata/empty/empty.exclude.txtar

@@ -0,0 +1,11 @@
+-- b.proto --
+syntax = "proto3";
+-- c.proto --
+syntax = "proto3";
+package pkg;
+message Foo {
+  string name = 1;
+}
+-- d.proto --
+syntax = "proto3";
+package pkg;

private/bufpkg/bufimage/bufimageutil/testdata/empty/empty.include.txtar

@@ -0,0 +1,3 @@
+-- a.proto --
+syntax = "proto3";
+package include;