Add build targets for Java lite runtime. (#3288)

* Add a protobuf_java_lite target for lite runtime.

* Add a cc_binary for javalite plugin.

* Add proto_lang_toolchain for Java lite.

BUILD

@@ -539,13 +539,100 @@ internal_gen_well_known_protos_java(
     srcs = WELL_KNOWN_PROTOS,
 )
 
+java_library(
+    name = "protobuf_java_lite",
+    srcs = [
+        "java/core/src/main/java/com/google/protobuf/AbstractMessageLite.java",
+        "java/core/src/main/java/com/google/protobuf/AbstractProtobufList.java",
+        "java/core/src/main/java/com/google/protobuf/AbstractParser.java",
+        "java/core/src/main/java/com/google/protobuf/BooleanArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/ByteBufferWriter.java",
+        "java/core/src/main/java/com/google/protobuf/ByteOutput.java",
+        "java/core/src/main/java/com/google/protobuf/ByteString.java",
+        "java/core/src/main/java/com/google/protobuf/CodedInputStream.java",
+        "java/core/src/main/java/com/google/protobuf/CodedOutputStream.java",
+        "java/core/src/main/java/com/google/protobuf/DoubleArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/ExperimentalApi.java",
+        "java/core/src/main/java/com/google/protobuf/ExtensionLite.java",
+        "java/core/src/main/java/com/google/protobuf/ExtensionRegistryFactory.java",
+        "java/core/src/main/java/com/google/protobuf/ExtensionRegistryLite.java",
+        "java/core/src/main/java/com/google/protobuf/FieldSet.java",
+        "java/core/src/main/java/com/google/protobuf/FloatArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java",
+        "java/core/src/main/java/com/google/protobuf/IntArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/Internal.java",
+        "java/core/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java",
+        "java/core/src/main/java/com/google/protobuf/LazyField.java",
+        "java/core/src/main/java/com/google/protobuf/LazyFieldLite.java",
+        "java/core/src/main/java/com/google/protobuf/LazyStringArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/LazyStringList.java",
+        "java/core/src/main/java/com/google/protobuf/LongArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/MapEntryLite.java",
+        "java/core/src/main/java/com/google/protobuf/MapFieldLite.java",
+        "java/core/src/main/java/com/google/protobuf/MessageLite.java",
+        "java/core/src/main/java/com/google/protobuf/MessageLiteOrBuilder.java",
+        "java/core/src/main/java/com/google/protobuf/MessageLiteToString.java",
+        "java/core/src/main/java/com/google/protobuf/MutabilityOracle.java",
+        "java/core/src/main/java/com/google/protobuf/NioByteString.java",
+        "java/core/src/main/java/com/google/protobuf/Parser.java",
+        "java/core/src/main/java/com/google/protobuf/ProtobufArrayList.java",
+        "java/core/src/main/java/com/google/protobuf/ProtocolStringList.java",
+        "java/core/src/main/java/com/google/protobuf/RopeByteString.java",
+        "java/core/src/main/java/com/google/protobuf/SmallSortedMap.java",
+        "java/core/src/main/java/com/google/protobuf/TextFormatEscaper.java",
+        "java/core/src/main/java/com/google/protobuf/UninitializedMessageException.java",
+        "java/core/src/main/java/com/google/protobuf/UnknownFieldSetLite.java",
+        "java/core/src/main/java/com/google/protobuf/UnsafeUtil.java",
+        "java/core/src/main/java/com/google/protobuf/UnmodifiableLazyStringList.java",
+        "java/core/src/main/java/com/google/protobuf/Utf8.java",
+        "java/core/src/main/java/com/google/protobuf/WireFormat.java",
+    ],
+    visibility = ["//visibility:public"],
+)
+
+cc_binary(
+    name = "protoc_gen_javalite",
+    srcs = ["src/google/protobuf/compiler/java/java_lite_main.cc"],
+    linkopts = LINK_OPTS,
+    visibility = ["//visibility:public"],
+    deps = [":protoc_lib"],
+)
+
 java_library(
     name = "protobuf_java",
-    srcs = glob([
-        "java/core/src/main/java/com/google/protobuf/*.java",
-    ]) + [
+    srcs = [
+        "java/core/src/main/java/com/google/protobuf/AbstractMessage.java",
+        "java/core/src/main/java/com/google/protobuf/BlockingRpcChannel.java",
+        "java/core/src/main/java/com/google/protobuf/BlockingService.java",
+        "java/core/src/main/java/com/google/protobuf/Descriptors.java",
+        "java/core/src/main/java/com/google/protobuf/DynamicMessage.java",
+        "java/core/src/main/java/com/google/protobuf/Extension.java",
+        "java/core/src/main/java/com/google/protobuf/ExtensionRegistry.java",
+        "java/core/src/main/java/com/google/protobuf/GeneratedMessage.java",
+        "java/core/src/main/java/com/google/protobuf/MapEntry.java",
+        "java/core/src/main/java/com/google/protobuf/MapField.java",
+        "java/core/src/main/java/com/google/protobuf/Message.java",
+        "java/core/src/main/java/com/google/protobuf/MessageOrBuilder.java",
+        "java/core/src/main/java/com/google/protobuf/MessageReflection.java",
+        "java/core/src/main/java/com/google/protobuf/ProtocolMessageEnum.java",
+        "java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java",
+        "java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilderV3.java",
+        "java/core/src/main/java/com/google/protobuf/RpcCallback.java",
+        "java/core/src/main/java/com/google/protobuf/RpcChannel.java",
+        "java/core/src/main/java/com/google/protobuf/RpcController.java",
+        "java/core/src/main/java/com/google/protobuf/RpcUtil.java",
+        "java/core/src/main/java/com/google/protobuf/Service.java",
+        "java/core/src/main/java/com/google/protobuf/ServiceException.java",
+        "java/core/src/main/java/com/google/protobuf/SingleFieldBuilder.java",
+        "java/core/src/main/java/com/google/protobuf/SingleFieldBuilderV3.java",
+        "java/core/src/main/java/com/google/protobuf/TextFormat.java",
+        "java/core/src/main/java/com/google/protobuf/TextFormatParseInfoTree.java",
+        "java/core/src/main/java/com/google/protobuf/TextFormatParseLocation.java",
+        "java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java",
+        "java/core/src/main/java/com/google/protobuf/UnsafeByteOperations.java",
         ":gen_well_known_protos_java",
     ],
+    deps = [":protobuf_java_lite"],
     visibility = ["//visibility:public"],
 )
 
@@ -772,3 +859,11 @@ proto_lang_toolchain(
     runtime = ":protobuf_java",
     visibility = ["//visibility:public"],
 )
+
+proto_lang_toolchain(
+    name = "javalite_toolchain",
+    command_line = "--$(PLUGIN_OUT)=$(OUT)",
+    plugin = ":protoc_gen_javalite",
+    runtime = ":protobuf_java_lite",
+    visibility = ["//visibility:public"],
+)

src/google/protobuf/compiler/java/java_message_lite.cc

@@ -392,6 +392,7 @@ void ImmutableMessageLiteGenerator::Generate(io::Printer* printer) {
 
   printer->Print(
     "}\n"
+    "// fall through\n"
     "case GET_DEFAULT_INSTANCE: {\n"
     "  return DEFAULT_INSTANCE;\n"
     "}\n"