proto: refactor merge tests

Use protobuild to generate test messages, both to simplify generating
proto2/proto3/extension variants of each test where appropriate and
to make it easier to test alternative message generators in the future.

Add various additional merge tests.

Change-Id: I4ba3ce232304e1d8325543680e2b6aae61de7364
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/219146
Reviewed-by: Joe Tsai <joetsai@google.com>

internal/protobuild/build.go

@@ -144,6 +144,8 @@ func fieldValue(fd pref.FieldDescriptor, v interface{}) pref.Value {
 		case pref.EnumKind:
 			v = fd.Enum().Values().ByName(pref.Name(o)).Number()
 		}
+	case []byte:
+		return pref.ValueOf(append([]byte{}, o...))
 	}
 	return pref.ValueOf(v)
 }

proto/testmessages_test.go

@@ -45,6 +45,22 @@ func makeMessages(in protobuild.Message, messages ...proto.Message) []proto.Mess
 	return messages
 }
 
+func templateMessages(messages ...proto.Message) []protoreflect.MessageType {
+	if len(messages) == 0 {
+		messages = []proto.Message{
+			(*testpb.TestAllTypes)(nil),
+			(*test3pb.TestAllTypes)(nil),
+			(*testpb.TestAllExtensions)(nil),
+		}
+	}
+	var out []protoreflect.MessageType
+	for _, m := range messages {
+		out = append(out, m.ProtoReflect().Type())
+	}
+	return out
+
+}
+
 var testValidMessages = []testProto{
 	{
 		desc:          "basic scalar types",

proto/weak_test.go

@@ -9,6 +9,7 @@ import (
 
 	"google.golang.org/protobuf/internal/encoding/pack"
 	"google.golang.org/protobuf/internal/flags"
+	"google.golang.org/protobuf/internal/protobuild"
 	"google.golang.org/protobuf/proto"
 
 	testpb "google.golang.org/protobuf/internal/testprotos/test"
@@ -19,6 +20,7 @@ func init() {
 	if flags.ProtoLegacy {
 		testValidMessages = append(testValidMessages, testWeakValidMessages...)
 		testInvalidMessages = append(testInvalidMessages, testWeakInvalidMessages...)
+		testMerges = append(testMerges, testWeakMerges...)
 	}
 }
 
@@ -65,6 +67,36 @@ var testWeakInvalidMessages = []testProto{
 	},
 }
 
+var testWeakMerges = []testMerge{
+	{
+		desc: "clone weak message",
+		src: protobuild.Message{
+			"weak_message1": protobuild.Message{
+				"a": 1,
+			},
+		},
+		types: []proto.Message{&testpb.TestWeak{}},
+	}, {
+		desc: "merge weak message",
+		dst: protobuild.Message{
+			"weak_message1": protobuild.Message{
+				"a": 1,
+			},
+		},
+		src: protobuild.Message{
+			"weak_message1": protobuild.Message{
+				"a": 2,
+			},
+		},
+		want: protobuild.Message{
+			"weak_message1": protobuild.Message{
+				"a": 2,
+			},
+		},
+		types: []proto.Message{&testpb.TestWeak{}},
+	},
+}
+
 func TestWeakNil(t *testing.T) {
 	if !flags.ProtoLegacy {
 		t.SkipNow()