Fix the NPE when there is message field type of google.protobuf.Empty

protoc-cli/src/main/java/io/ballerina/protoc/builder/stub/Field.java

@@ -137,7 +137,7 @@ public Field build() {
 
         private Builder(DescriptorProtos.FieldDescriptorProto fieldDescriptor, String fieldType) {
             this.fieldDescriptor = fieldDescriptor;
-            this.type = fieldType;
+            this.type = fieldType != null ? fieldType : "empty:Empty";
         }
     }
 

protoc-cli/src/main/java/module-info.java

@@ -28,4 +28,5 @@
     requires info.picocli;
     requires org.slf4j;
     requires org.apache.commons.lang3;
+    requires protobuf.java;
 }

tooling-tests/src/test/java/io/ballerina/protoc/tools/ToolingUnaryTest.java

@@ -96,4 +96,11 @@ public void testUnaryHelloWorldTimestamp() {
                 "helloWorldTimestamp_pb.bal", "helloworld_service.bal",
                 "helloworld_client.bal", "tool_test_unary_10");
     }
+
+    @Test
+    public void testUnaryWithEmptyFieldMessage() {
+        assertGeneratedSources("unary", "emptyFieldMessage.proto",
+                "emptyFieldMessage_pb.bal", "testservice_service.bal",
+                "testservice_client.bal", "tool_test_unary_11");
+    }
 }

tooling-tests/src/test/resources/test-src/generated-sources/tool_test_unary_11/emptyFieldMessage_pb.bal

@@ -0,0 +1,119 @@
+import ballerina/grpc;
+import ballerina/protobuf;
+import ballerina/protobuf.types.empty;
+
+public const string EMPTYFIELDMESSAGE_DESC = "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";
+
+public isolated client class TestServiceClient {
+    *grpc:AbstractClientEndpoint;
+
+    private final grpc:Client grpcClient;
+
+    public isolated function init(string url, *grpc:ClientConfiguration config) returns grpc:Error? {
+        self.grpcClient = check new (url, config);
+        check self.grpcClient.initStub(self, EMPTYFIELDMESSAGE_DESC);
+    }
+
+    isolated remote function TestRPC(RequestMessage|ContextRequestMessage req) returns ResponseMessage|grpc:Error {
+        map<string|string[]> headers = {};
+        RequestMessage message;
+        if req is ContextRequestMessage {
+            message = req.content;
+            headers = req.headers;
+        } else {
+            message = req;
+        }
+        var payload = check self.grpcClient->executeSimpleRPC("test.TestService/TestRPC", message, headers);
+        [anydata, map<string|string[]>] [result, _] = payload;
+        return <ResponseMessage>result;
+    }
+
+    isolated remote function TestRPCContext(RequestMessage|ContextRequestMessage req) returns ContextResponseMessage|grpc:Error {
+        map<string|string[]> headers = {};
+        RequestMessage message;
+        if req is ContextRequestMessage {
+            message = req.content;
+            headers = req.headers;
+        } else {
+            message = req;
+        }
+        var payload = check self.grpcClient->executeSimpleRPC("test.TestService/TestRPC", message, headers);
+        [anydata, map<string|string[]>] [result, respHeaders] = payload;
+        return {content: <ResponseMessage>result, headers: respHeaders};
+    }
+}
+
+public isolated client class TestServiceResponseMessageCaller {
+    private final grpc:Caller caller;
+
+    public isolated function init(grpc:Caller caller) {
+        self.caller = caller;
+    }
+
+    public isolated function getId() returns int {
+        return self.caller.getId();
+    }
+
+    isolated remote function sendResponseMessage(ResponseMessage response) returns grpc:Error? {
+        return self.caller->send(response);
+    }
+
+    isolated remote function sendContextResponseMessage(ContextResponseMessage response) returns grpc:Error? {
+        return self.caller->send(response);
+    }
+
+    isolated remote function sendError(grpc:Error response) returns grpc:Error? {
+        return self.caller->sendError(response);
+    }
+
+    isolated remote function complete() returns grpc:Error? {
+        return self.caller->complete();
+    }
+
+    public isolated function isCancelled() returns boolean {
+        return self.caller.isCancelled();
+    }
+}
+
+public type ContextRequestMessage record {|
+    RequestMessage content;
+    map<string|string[]> headers;
+|};
+
+public type ContextResponseMessage record {|
+    ResponseMessage content;
+    map<string|string[]> headers;
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type RequestMessage record {|
+    OptionalComplexType[] req = [];
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type OptionalComplexType record {|
+    ComplexType complex_value = {};
+    empty:Empty none = {};
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type ResponseMessage record {|
+    OptionalString[] resp = [];
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type OptionalString record {|
+    string name = "";
+    empty:Empty none = {};
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type ComplexType record {|
+    int:Unsigned32 foo = 0;
+    TestEnum bar = ENTRY_ONE;
+|};
+
+public enum TestEnum {
+    ENTRY_ONE, ENTRY_TWO
+}
+

tooling-tests/src/test/resources/test-src/generated-sources/tool_test_unary_11/emptyFieldMessage_pb_client.bal

@@ -0,0 +1,87 @@
+import ballerina/grpc;
+import ballerina/protobuf;
+import ballerina/protobuf.types.empty;
+
+public const string EMPTYFIELDMESSAGE_DESC = "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";
+
+public isolated client class TestServiceClient {
+    *grpc:AbstractClientEndpoint;
+
+    private final grpc:Client grpcClient;
+
+    public isolated function init(string url, *grpc:ClientConfiguration config) returns grpc:Error? {
+        self.grpcClient = check new (url, config);
+        check self.grpcClient.initStub(self, EMPTYFIELDMESSAGE_DESC);
+    }
+
+    isolated remote function TestRPC(RequestMessage|ContextRequestMessage req) returns ResponseMessage|grpc:Error {
+        map<string|string[]> headers = {};
+        RequestMessage message;
+        if req is ContextRequestMessage {
+            message = req.content;
+            headers = req.headers;
+        } else {
+            message = req;
+        }
+        var payload = check self.grpcClient->executeSimpleRPC("test.TestService/TestRPC", message, headers);
+        [anydata, map<string|string[]>] [result, _] = payload;
+        return <ResponseMessage>result;
+    }
+
+    isolated remote function TestRPCContext(RequestMessage|ContextRequestMessage req) returns ContextResponseMessage|grpc:Error {
+        map<string|string[]> headers = {};
+        RequestMessage message;
+        if req is ContextRequestMessage {
+            message = req.content;
+            headers = req.headers;
+        } else {
+            message = req;
+        }
+        var payload = check self.grpcClient->executeSimpleRPC("test.TestService/TestRPC", message, headers);
+        [anydata, map<string|string[]>] [result, respHeaders] = payload;
+        return {content: <ResponseMessage>result, headers: respHeaders};
+    }
+}
+
+public type ContextRequestMessage record {|
+    RequestMessage content;
+    map<string|string[]> headers;
+|};
+
+public type ContextResponseMessage record {|
+    ResponseMessage content;
+    map<string|string[]> headers;
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type RequestMessage record {|
+    OptionalComplexType[] req = [];
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type OptionalComplexType record {|
+    ComplexType complex_value = {};
+    empty:Empty none = {};
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type ResponseMessage record {|
+    OptionalString[] resp = [];
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type OptionalString record {|
+    string name = "";
+    empty:Empty none = {};
+|};
+
+@protobuf:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+public type ComplexType record {|
+    int:Unsigned32 foo = 0;
+    TestEnum bar = ENTRY_ONE;
+|};
+
+public enum TestEnum {
+    ENTRY_ONE, ENTRY_TWO
+}
+

tooling-tests/src/test/resources/test-src/generated-sources/tool_test_unary_11/testservice_client.bal

@@ -0,0 +1,10 @@
+import ballerina/io;
+
+TestServiceClient ep = check new ("http://localhost:9090");
+
+public function main() returns error? {
+    RequestMessage testRPCRequest = {req: [{complex_value: {foo: 1, bar: "ENTRY_ONE"}, none: {}}]};
+    ResponseMessage testRPCResponse = check ep->TestRPC(testRPCRequest);
+    io:println(testRPCResponse);
+}
+

tooling-tests/src/test/resources/test-src/generated-sources/tool_test_unary_11/testservice_service.bal

@@ -0,0 +1,11 @@
+import ballerina/grpc;
+
+listener grpc:Listener ep = new (9090);
+
+@grpc:Descriptor {value: EMPTYFIELDMESSAGE_DESC}
+service "TestService" on ep {
+
+    remote function TestRPC(RequestMessage value) returns ResponseMessage|error {
+    }
+}
+

tooling-tests/src/test/resources/test-src/proto-files/unary/emptyFieldMessage.proto

@@ -0,0 +1,55 @@
+/*
+ *  Copyright (c) 2024, WSO2 LLC. (http://www.wso2.org).
+ *
+ *  WSO2 LLC. licenses this file to you 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 test;
+
+import "google/protobuf/empty.proto";
+
+service TestService {
+    rpc TestRPC(RequestMessage) returns (ResponseMessage);
+}
+
+enum TestEnum {
+    ENTRY_ONE = 0;
+    ENTRY_TWO = 1;
+}
+
+message ComplexType {
+    uint32 foo = 1;
+    TestEnum bar = 2;
+}
+
+message OptionalComplexType {
+    ComplexType complex_value = 1;
+    google.protobuf.Empty none = 2;
+}
+
+message OptionalString {
+    string name = 1;
+    google.protobuf.Empty none = 2;
+}
+
+message RequestMessage {
+    repeated OptionalComplexType req = 1;
+}
+
+message ResponseMessage {
+    repeated OptionalString resp = 1;
+}