Wrap primitive and array parameter into an array as in JSON-RPC 2.0

org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/json/adapters/MessageTypeAdapter.java

@@ -15,6 +15,7 @@
 import java.io.IOException;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
 
@@ -42,6 +43,7 @@
 import com.google.gson.JsonSyntaxException;
 import com.google.gson.TypeAdapter;
 import com.google.gson.TypeAdapterFactory;
+import com.google.gson.internal.Primitives;
 import com.google.gson.reflect.TypeToken;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
@@ -266,12 +268,19 @@ protected Object parseParams(JsonReader in, String method) throws IOException, J
 			List<Object> parameters = new ArrayList<Object>(parameterTypes.length);
 			int index = 0;
 			in.beginArray();
+			boolean wrappedArray = in.peek() == JsonToken.BEGIN_ARRAY;
+			if(wrappedArray) {
+				in.beginArray();
+			}
 			while (in.hasNext()) {
 				Type parameterType = index < parameterTypes.length ? parameterTypes[index] : null;
 				Object parameter = fromJson(in, parameterType);
 				parameters.add(parameter);
 				index++;
 			}
+			if(wrappedArray) {
+				in.endArray();
+			}
 			in.endArray();
 			while (index < parameterTypes.length) {
 				parameters.add(null);
@@ -420,7 +429,7 @@ public void write(JsonWriter out, Message message) throws IOException {
 			if (params == null)
 				writeNullValue(out);
 			else
-				gson.toJson(params, params.getClass(), out);
+				handleParameter(out, params);
 		} else if (message instanceof ResponseMessage) {
 			ResponseMessage responseMessage = (ResponseMessage) message;
 			out.name("id");
@@ -445,12 +454,24 @@ public void write(JsonWriter out, Message message) throws IOException {
 			if (params == null)
 				writeNullValue(out);
 			else
-				gson.toJson(params, params.getClass(), out);
+				handleParameter(out, params);
 		}
 
 		out.endObject();
 	}
 
+	protected void handleParameter(JsonWriter out, Object params) {
+		if(Collection.class.isInstance(params)
+				|| params.getClass().isArray()
+				|| params instanceof String
+				|| Primitives.isPrimitive(getClass())
+				|| Primitives.isWrapperType(params.getClass())) {
+			gson.toJson(List.of(params), List.class, out);
+		} else {
+			gson.toJson(params, params.getClass(), out);
+		}
+	}
+
 	protected void writeId(JsonWriter out, Either<String, Number> id) throws IOException {
 		if (id == null)
 			writeNullValue(out);

org.eclipse.lsp4j.jsonrpc/src/test/java/org/eclipse/lsp4j/jsonrpc/test/json/MessageJsonHandlerTest.java

@@ -138,7 +138,7 @@ public void testSerializeEmptyList() {
 		message.setMethod("foo");
 		message.setParams(Collections.EMPTY_LIST);
 		String json = handler.serialize(message);
-		Assert.assertEquals("{\"jsonrpc\":\"2.0\",\"method\":\"foo\",\"params\":[]}", json);
+		Assert.assertEquals("{\"jsonrpc\":\"2.0\",\"method\":\"foo\",\"params\":[[]]}", json);
 	}
 
 	@Test
@@ -151,7 +151,7 @@ public void testSerializeImmutableList() {
 		list.add("b");
 		message.setParams(Collections.unmodifiableList(list));
 		String json = handler.serialize(message);
-		Assert.assertEquals("{\"jsonrpc\":\"2.0\",\"method\":\"foo\",\"params\":[\"a\",\"b\"]}", json);
+		Assert.assertEquals("{\"jsonrpc\":\"2.0\",\"method\":\"foo\",\"params\":[[\"a\",\"b\"]]}", json);
 	}
 
 	@SuppressWarnings({ "unchecked" })
@@ -437,7 +437,7 @@ public void testRawMultiParamsParsing_03() {
 		RequestMessage message = (RequestMessage) handler.parseMessage("{\"jsonrpc\":\"2.0\","
 				+ "\"id\":\"2\",\n"
 				+ "\"method\":\"foo\",\n"
-				+ "\"params\": [[\"foo\", \"bar\"], [1, 2], {\"uri\": \"dummy://mymodel.mydsl\"}]\n"
+				+ "\"params\": [[[\"foo\", \"bar\"], [1, 2], {\"uri\": \"dummy://mymodel.mydsl\"}]]\n"
 				+ "}");
 		Assert.assertTrue("" + message.getParams().getClass(), message.getParams() instanceof List);
 
@@ -462,7 +462,7 @@ public void testRawMultiParamsParsing_04() {
 		RequestMessage message = (RequestMessage) handler.parseMessage("{\"jsonrpc\":\"2.0\","
 				+ "\"id\":\"2\",\n"
 				+ "\"method\":\"foo\",\n"
-				+ "\"params\": [[\"foo\", \"bar\"], [1, 2]]\n"
+				+ "\"params\": [[[\"foo\", \"bar\"], [1, 2]]]\n"
 				+ "}");
 		Assert.assertTrue("" + message.getParams().getClass(), message.getParams() instanceof List);
 
@@ -792,13 +792,41 @@ public void testParamUnwrap_JsonRpc2_0() {
 		var request = new RequestMessage();
 		request.setId(1);
 		request.setMethod(handler.getMethodProvider().resolveMethod(null));
-		request.setParams(new boolean[] { true }); // fake wrapped primitive [true] for JsonRpc 2.0
+		request.setParams(true); // fake wrapped primitive [true] for JsonRpc 2.0
 
 		RequestMessage message = (RequestMessage) handler.parseMessage(request.toString());
 
 		// Check parse - unwrap primitive
 		assertEquals(true, message.getParams());
+	}
+
+	@Test
+	public void testParamWrap_JsonRpc2_0() {
+		MessageJsonHandler handler = createSimpleRequestHandler(String.class, Boolean.class);
+
+		var request = new RequestMessage();
+		request.setMethod(handler.getMethodProvider().resolveMethod(null));
+		request.setParams(true);
+
+		// Check serialize - wrap primitive
+		assertEquals("{\"jsonrpc\":\"2.0\",\"id\":null,\"method\":\"testMethod\",\"params\":[true]}", handler.serialize(request));
 
+		request.setParams(Boolean.TRUE);
+		// Check serialize - wrap primitive wrapper
+		assertEquals("{\"jsonrpc\":\"2.0\",\"id\":null,\"method\":\"testMethod\",\"params\":[true]}", handler.serialize(request));
+	}
+
+	@Test
+	public void testParamWrapString_JsonRpc2_0() {
+		MessageJsonHandler handler = createSimpleRequestHandler(String.class, String.class);
+
+		var request = new RequestMessage();
+		request.setMethod(handler.getMethodProvider().resolveMethod(null));
+		request.setParams("some string");
+
+		// Check serialize - wrap primitive
+		assertEquals("{\"jsonrpc\":\"2.0\",\"id\":null,\"method\":\"testMethod\",\"params\":[\"some string\"]}",
+				handler.serialize(request));
 	}
 
 	@Test
@@ -818,6 +846,23 @@ public void testArrayParamUnwrap_JsonRpc2_0() {
 
 	}
 
+	@Test
+	public void testArrayParamWrap_JsonRpc2_0() {
+		MessageJsonHandler handler = createSimpleRequestHandler(String.class, new TypeToken<List<Boolean>>() {
+		}.getType());
+
+		var request = new RequestMessage();
+		request.setMethod(handler.getMethodProvider().resolveMethod(null));
+		request.setParams(new Boolean[] { true, false });
+		// Check serialize - wrap primitive wrapper
+		assertEquals("{\"jsonrpc\":\"2.0\",\"id\":null,\"method\":\"testMethod\",\"params\":[[true,false]]}",
+				handler.serialize(request));
+		request.setParams(List.of(true, false));
+		// Check serialize - wrap primitive wrapper
+		assertEquals("{\"jsonrpc\":\"2.0\",\"id\":null,\"method\":\"testMethod\",\"params\":[[true,false]]}",
+				handler.serialize(request));
+	}
+
 	@Test
 	public void testMultiParamUnwrap_JsonRpc2_0() {
 		MessageJsonHandler handler = createSimpleRequestHandler(String.class, Boolean.class, String.class);