Fix unused dependencies on type filters for buf generate (#3695)

Author: emcfarlane

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Fix use of deprecated flag `--include-types` for `buf generate`.
 - Add `--against-registry` flag to `buf breaking` that runs breaking checks against the latest
   commit on the default branch of the corresponding module in the registry.
+- Fix type filter with unused image dependencies for `buf generate`.
 
 ## [v1.50.1] - 2025-03-10
 

private/bufpkg/bufimage/bufimageutil/bufimageutil.go

@@ -244,7 +244,6 @@ func ImageFilteredByTypesWithOptions(image bufimage.Image, types []string, opts
 		if !ok {
 			continue
 		}
-		includedFiles = append(includedFiles, imageFile)
 		imageFileDescriptor := imageFile.FileDescriptorProto()
 
 		importsRequired := closure.imports[imageFile.Path()]
@@ -365,6 +364,20 @@ func ImageFilteredByTypesWithOptions(image bufimage.Image, types []string, opts
 			}
 			imageFileDescriptor.SourceCodeInfo.Location = imageFileDescriptor.SourceCodeInfo.Location[:i]
 		}
+		imageFile, err = bufimage.NewImageFile(
+			imageFileDescriptor,
+			imageFile.FullName(),
+			imageFile.CommitID(),
+			imageFile.ExternalPath(),
+			imageFile.LocalPath(),
+			imageFile.IsImport(),
+			imageFile.IsSyntaxUnspecified(),
+			nil, // There are no unused dependencies.
+		)
+		if err != nil {
+			return nil, err
+		}
+		includedFiles = append(includedFiles, imageFile)
 	}
 	return bufimage.NewImage(includedFiles)
 }

private/bufpkg/bufimage/bufimageutil/bufimageutil_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/bufbuild/buf/private/bufpkg/bufmodule"
 	"github.com/bufbuild/buf/private/bufpkg/bufmodule/bufmoduletesting"
 	"github.com/bufbuild/buf/private/pkg/protoencoding"
+	"github.com/bufbuild/buf/private/pkg/slicesext"
 	"github.com/bufbuild/buf/private/pkg/slogtestext"
 	"github.com/bufbuild/buf/private/pkg/storage"
 	"github.com/bufbuild/buf/private/pkg/storage/storageos"
@@ -161,6 +162,11 @@ func TestSourceCodeInfo(t *testing.T) {
 	runSourceCodeInfoTest(t, "foo.bar", "all.txtar")
 }
 
+func TestUnusedDeps(t *testing.T) {
+	t.Parallel()
+	runDiffTest(t, "testdata/unuseddeps", []string{"a.A"}, "a.txtar")
+}
+
 func TestTransitivePublic(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
@@ -264,16 +270,23 @@ func runDiffTest(t *testing.T, testdataDir string, typenames []string, expectedF
 	assert.NotNil(t, image)
 	assert.True(t, imageIsDependencyOrdered(filteredImage), "image files not in dependency order")
 
+	// Convert the filtered image back to a proto image and then back to an image to ensure that the
+	// image is still valid after filtering.
+	protoImage, err := bufimage.ImageToProtoImage(filteredImage)
+	require.NoError(t, err)
+	filteredImage, err = bufimage.NewImageForProto(protoImage)
+	require.NoError(t, err)
+
 	// We may have filtered out custom options from the set in the step above. However, the options messages
 	// still contain extension fields that refer to the custom options, as a result of building the image.
 	// So we serialize and then de-serialize, and use only the filtered results to parse extensions. That
 	// way, the result will omit custom options that aren't present in the filtered set (as they will be
 	// considered unrecognized fields).
-	data, err := protoencoding.NewWireMarshaler().Marshal(bufimage.ImageToFileDescriptorSet(filteredImage))
-	require.NoError(t, err)
-	fileDescriptorSet := &descriptorpb.FileDescriptorSet{}
-	err = protoencoding.NewWireUnmarshaler(filteredImage.Resolver()).Unmarshal(data, fileDescriptorSet)
-	require.NoError(t, err)
+	fileDescriptorSet := &descriptorpb.FileDescriptorSet{
+		File: slicesext.Map(filteredImage.Files(), func(imageFile bufimage.ImageFile) *descriptorpb.FileDescriptorProto {
+			return imageFile.FileDescriptorProto()
+		}),
+	}
 
 	files, err := protodesc.NewFiles(fileDescriptorSet)
 	require.NoError(t, err)

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

@@ -0,0 +1,7 @@
+syntax = "proto3";
+package a;
+import "b.proto";
+import "c.proto";
+message A{
+	b.B b = 1;
+}

private/bufpkg/bufimage/bufimageutil/testdata/unuseddeps/a.txtar

@@ -0,0 +1,12 @@
+-- a.proto --
+syntax = "proto3";
+package a;
+import "b.proto";
+message A {
+  b.B b = 1;
+}
+-- b.proto --
+syntax = "proto3";
+package b;
+message B {
+}

private/bufpkg/bufimage/bufimageutil/testdata/unuseddeps/ab.txtar

@@ -0,0 +1,5 @@
+-- a.proto --
+syntax = "proto3";
+package a;
+message A {
+}

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

@@ -0,0 +1,4 @@
+syntax = "proto3";
+package b;
+import "c.proto";
+message B {}

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

@@ -0,0 +1,3 @@
+syntax = "proto3";
+package c;
+message C {}