Adds some proto3 java tests for Empty (square#1645)

wire-protoc-compatibility-tests/src/main/proto/squareup/proto3/java/alltypes/all_empty.proto

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2020 Square Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+syntax = "proto3";
+package squareup.proto3.java.alltypes;
+
+import "google/protobuf/empty.proto";
+
+message AllEmpty {
+  google.protobuf.Empty empty = 1;
+
+  repeated google.protobuf.Empty rep_empty = 201;
+
+  oneof choice {
+    google.protobuf.Empty oneof_empty = 402;
+  }
+
+  map<int32, google.protobuf.Empty> map_int32_empty = 501;
+}

wire-protoc-compatibility-tests/src/test/java/com/squareup/wire/EmptyRoundTripTest.kt

@@ -20,6 +20,7 @@ import org.assertj.core.api.Assertions.assertThat
 import org.junit.Test
 import squareup.proto3.kotlin.alltypes.AllEmptyOuterClass
 import squareup.proto3.kotlin.alltypes.AllEmpty as AllEmptyK
+import squareup.proto3.java.alltypes.AllEmpty as AllEmptyJ
 
 class EmptyRoundTripTest {
   @Test fun empty() {
@@ -42,18 +43,30 @@ class EmptyRoundTripTest {
         .setOneofEmpty(Empty.newBuilder().build())
         .build()
 
-    val wireMessage = AllEmptyK(
+    val wireMessageJava = AllEmptyJ.Builder()
+        .empty(Unit)
+        .rep_empty(listOf(Unit, Unit))
+        .map_int32_empty(mapOf(1 to Unit))
+        .oneof_empty(Unit)
+        .build()
+
+    val wireMessageKotlin = AllEmptyK(
         empty = Unit,
         rep_empty = listOf(Unit, Unit),
         map_int32_empty = mapOf(1 to Unit),
         oneof_empty = Unit
     )
 
     val googleMessageBytes = googleMessage.toByteArray()
-    val wireMessageBytes = AllEmptyK.ADAPTER.encode(wireMessage)
-    assertThat(AllEmptyOuterClass.AllEmpty.parseFrom(wireMessageBytes)).isEqualTo(googleMessage)
-    assertThat(AllEmptyK.ADAPTER.decode(wireMessageBytes)).isEqualTo(wireMessage)
-    assertThat(AllEmptyK.ADAPTER.decode(googleMessageBytes)).isEqualTo(wireMessage)
-    assertThat(AllEmptyK.ADAPTER.encodedSize(wireMessage)).isEqualTo(googleMessageBytes.size)
+    val wireMessageJavaBytes = AllEmptyJ.ADAPTER.encode(wireMessageJava)
+    assertThat(AllEmptyOuterClass.AllEmpty.parseFrom(wireMessageJavaBytes)).isEqualTo(googleMessage)
+    assertThat(AllEmptyJ.ADAPTER.decode(wireMessageJavaBytes)).isEqualTo(wireMessageJava)
+    assertThat(AllEmptyJ.ADAPTER.decode(googleMessageBytes)).isEqualTo(wireMessageJava)
+    assertThat(AllEmptyJ.ADAPTER.encodedSize(wireMessageJava)).isEqualTo(googleMessageBytes.size)
+    val wireMessageKotlinBytes = AllEmptyK.ADAPTER.encode(wireMessageKotlin)
+    assertThat(AllEmptyOuterClass.AllEmpty.parseFrom(wireMessageKotlinBytes)).isEqualTo(googleMessage)
+    assertThat(AllEmptyK.ADAPTER.decode(wireMessageKotlinBytes)).isEqualTo(wireMessageKotlin)
+    assertThat(AllEmptyK.ADAPTER.decode(googleMessageBytes)).isEqualTo(wireMessageKotlin)
+    assertThat(AllEmptyK.ADAPTER.encodedSize(wireMessageKotlin)).isEqualTo(googleMessageBytes.size)
   }
 }