reflect/protoregistry: permit conflicting file names

Remove the requirement that all registered files have unique names.

Files.FindFileByPath now returns an error if multiple files match
the path. Files.RangeFiles iterates over all files, including ones with
the same name.

Unlike descriptor names, file names are not part of any of the wire
encodings. Conflicts in file names only affect file lookups by path,
which is an uncommon operation.

The Files.RegisterFile documentation already states (inaccurately),
"It is permitted for multiple files to have the same file path."
This change brings the behavior of RegisterFile in line with the
documentation.

Fixes golang/protobuf#1122

Change-Id: I2750e35736fd34def23fa6ab6d6a829095a65a26
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/321531
Trust: Damien Neil <dneil@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

reflect/protoregistry/registry.go

@@ -94,7 +94,8 @@ type Files struct {
 	// Note that enum values are in the top-level since that are in the same
 	// scope as the parent enum.
 	descsByName map[protoreflect.FullName]interface{}
-	filesByPath map[string]protoreflect.FileDescriptor
+	filesByPath map[string][]protoreflect.FileDescriptor
+	numFiles    int
 }
 
 type packageDescriptor struct {
@@ -117,17 +118,11 @@ func (r *Files) RegisterFile(file protoreflect.FileDescriptor) error {
 		r.descsByName = map[protoreflect.FullName]interface{}{
 			"": &packageDescriptor{},
 		}
-		r.filesByPath = make(map[string]protoreflect.FileDescriptor)
+		r.filesByPath = make(map[string][]protoreflect.FileDescriptor)
 	}
 	path := file.Path()
-	if prev := r.filesByPath[path]; prev != nil {
+	if len(r.filesByPath[path]) > 0 {
 		r.checkGenProtoConflict(path)
-		err := errors.New("file %q is already registered", file.Path())
-		err = amendErrorWithCaller(err, prev, file)
-		if r == GlobalFiles && ignoreConflict(file, err) {
-			err = nil
-		}
-		return err
 	}
 
 	for name := file.Package(); name != ""; name = name.Parent() {
@@ -168,7 +163,8 @@ func (r *Files) RegisterFile(file protoreflect.FileDescriptor) error {
 	rangeTopLevelDescriptors(file, func(d protoreflect.Descriptor) {
 		r.descsByName[d.FullName()] = d
 	})
-	r.filesByPath[path] = file
+	r.filesByPath[path] = append(r.filesByPath[path], file)
+	r.numFiles++
 	return nil
 }
 
@@ -308,6 +304,7 @@ func (s *nameSuffix) Pop() (name protoreflect.Name) {
 // FindFileByPath looks up a file by the path.
 //
 // This returns (nil, NotFound) if not found.
+// This returns an error if multiple files have the same path.
 func (r *Files) FindFileByPath(path string) (protoreflect.FileDescriptor, error) {
 	if r == nil {
 		return nil, NotFound
@@ -316,13 +313,19 @@ func (r *Files) FindFileByPath(path string) (protoreflect.FileDescriptor, error)
 		globalMutex.RLock()
 		defer globalMutex.RUnlock()
 	}
-	if fd, ok := r.filesByPath[path]; ok {
-		return fd, nil
+	fds := r.filesByPath[path]
+	switch len(fds) {
+	case 0:
+		return nil, NotFound
+	case 1:
+		return fds[0], nil
+	default:
+		return nil, errors.New("multiple files named %q", path)
 	}
-	return nil, NotFound
 }
 
-// NumFiles reports the number of registered files.
+// NumFiles reports the number of registered files,
+// including duplicate files with the same name.
 func (r *Files) NumFiles() int {
 	if r == nil {
 		return 0
@@ -331,10 +334,11 @@ func (r *Files) NumFiles() int {
 		globalMutex.RLock()
 		defer globalMutex.RUnlock()
 	}
-	return len(r.filesByPath)
+	return r.numFiles
 }
 
 // RangeFiles iterates over all registered files while f returns true.
+// If multiple files have the same name, RangeFiles iterates over all of them.
 // The iteration order is undefined.
 func (r *Files) RangeFiles(f func(protoreflect.FileDescriptor) bool) {
 	if r == nil {
@@ -344,9 +348,11 @@ func (r *Files) RangeFiles(f func(protoreflect.FileDescriptor) bool) {
 		globalMutex.RLock()
 		defer globalMutex.RUnlock()
 	}
-	for _, file := range r.filesByPath {
-		if !f(file) {
-			return
+	for _, files := range r.filesByPath {
+		for _, file := range files {
+			if !f(file) {
+				return
+			}
 		}
 	}
 }

reflect/protoregistry/registry_test.go

@@ -55,6 +55,7 @@ func TestFiles(t *testing.T) {
 		testFindPath struct {
 			inPath    string
 			wantFiles []file
+			wantErr   string
 		}
 	)
 
@@ -68,7 +69,7 @@ func TestFiles(t *testing.T) {
 		files: []testFile{
 			{inFile: mustMakeFile(`syntax:"proto2" name:"test1.proto" package:"foo.bar"`)},
 			{inFile: mustMakeFile(`syntax:"proto2" name:"foo/bar/test.proto" package:"my.test"`)},
-			{inFile: mustMakeFile(`syntax:"proto2" name:"foo/bar/test.proto" package:"foo.bar.baz"`), wantErr: "already registered"},
+			{inFile: mustMakeFile(`syntax:"proto2" name:"foo/bar/test.proto" package:"foo.bar.baz"`)},
 			{inFile: mustMakeFile(`syntax:"proto2" name:"test2.proto" package:"my.test.package"`)},
 			{inFile: mustMakeFile(`syntax:"proto2" name:"weird" package:"foo.bar"`)},
 			{inFile: mustMakeFile(`syntax:"proto2" name:"foo/bar/baz/../test.proto" package:"my.test"`)},
@@ -103,17 +104,16 @@ func TestFiles(t *testing.T) {
 		}},
 
 		findPaths: []testFindPath{{
-			inPath: "nothing",
+			inPath:  "nothing",
+			wantErr: "not found",
 		}, {
 			inPath: "weird",
 			wantFiles: []file{
 				{"weird", "foo.bar"},
 			},
 		}, {
-			inPath: "foo/bar/test.proto",
-			wantFiles: []file{
-				{"foo/bar/test.proto", "my.test"},
-			},
+			inPath:  "foo/bar/test.proto",
+			wantErr: `multiple files named "foo/bar/test.proto"`,
 		}},
 	}, {
 		// Test when new enum conflicts with existing package.
@@ -315,9 +315,13 @@ func TestFiles(t *testing.T) {
 
 			for _, tc := range tt.findPaths {
 				var gotFiles []file
-				if fd, err := files.FindFileByPath(tc.inPath); err == nil {
+				fd, gotErr := files.FindFileByPath(tc.inPath)
+				if gotErr == nil {
 					gotFiles = append(gotFiles, file{fd.Path(), fd.Package()})
 				}
+				if ((gotErr == nil) != (tc.wantErr == "")) || !strings.Contains(fmt.Sprint(gotErr), tc.wantErr) {
+					t.Errorf("FindFileByPath(%v) = %v, want %v", tc.inPath, gotErr, tc.wantErr)
+				}
 				if diff := cmp.Diff(tc.wantFiles, gotFiles, sortFiles); diff != "" {
 					t.Errorf("FindFileByPath(%v) mismatch (-want +got):\n%v", tc.inPath, diff)
 				}