fix: Use a single Gson instance which knows about the Either type

Author: FlorianKroiss

org.eclipse.lsp4e/src/org/eclipse/lsp4e/LanguageServerWrapper.java

@@ -18,7 +18,7 @@
  *******************************************************************************/
 package org.eclipse.lsp4e;
 
-import static org.eclipse.lsp4e.internal.NullSafetyHelper.*;
+import static org.eclipse.lsp4e.internal.NullSafetyHelper.castNonNull;
 
 import java.io.BufferedReader;
 import java.io.File;
@@ -119,6 +119,7 @@
 import org.eclipse.lsp4j.jsonrpc.Launcher;
 import org.eclipse.lsp4j.jsonrpc.MessageConsumer;
 import org.eclipse.lsp4j.jsonrpc.ResponseErrorException;
+import org.eclipse.lsp4j.jsonrpc.json.adapters.EitherTypeAdapter;
 import org.eclipse.lsp4j.jsonrpc.messages.Either;
 import org.eclipse.lsp4j.jsonrpc.messages.Message;
 import org.eclipse.lsp4j.jsonrpc.messages.ResponseErrorCode;
@@ -130,6 +131,7 @@
 import com.google.common.base.Functions;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import com.google.gson.JsonObject;
 
 public class LanguageServerWrapper {
@@ -251,6 +253,10 @@ synchronized void close() {
 		}
 	}
 
+	private static final Gson GSON = new GsonBuilder()
+			.registerTypeAdapterFactory(new EitherTypeAdapter.Factory())
+			.create();
+
 	public final LanguageServerDefinition serverDefinition;
 	public final @Nullable IProject initialProject;
 	protected Map<URI, DocumentContentSynchronizer> connectedDocuments;
@@ -1173,7 +1179,7 @@ public void registerCapability(RegistrationParams params) {
 				break;
 			case "workspace/executeCommand": //$NON-NLS-1$
 				try {
-					ExecuteCommandOptions executeCommandOptions = castNonNull(new Gson().fromJson((JsonObject) reg.getRegisterOptions(),
+					ExecuteCommandOptions executeCommandOptions = castNonNull(GSON.fromJson((JsonObject) reg.getRegisterOptions(),
 							ExecuteCommandOptions.class));
 					List<String> newCommands = executeCommandOptions.getCommands();
 					if (!newCommands.isEmpty()) {
@@ -1212,7 +1218,7 @@ public void registerCapability(RegistrationParams params) {
 			case "textDocument/completion": { //$NON-NLS-1$
 				CompletionOptions previous = serverCapabilities.getCompletionProvider();
 				try {
-					final var completionOpts = new Gson().fromJson((JsonObject) reg.getRegisterOptions(),
+					final var completionOpts = GSON.fromJson((JsonObject) reg.getRegisterOptions(),
 							CompletionOptions.class);
 					serverCapabilities.setCompletionProvider(completionOpts);
 					addRegistration(reg, () -> serverCapabilities.setCompletionProvider(previous));
@@ -1255,8 +1261,9 @@ public void registerCapability(RegistrationParams params) {
 			return null;
 		if (registerOptions instanceof DidChangeWatchedFilesRegistrationOptions direct)
 			return direct;
-		if (registerOptions instanceof JsonObject jsonObject)
-			return new Gson().fromJson(jsonObject, DidChangeWatchedFilesRegistrationOptions.class);
+		if (registerOptions instanceof JsonObject jsonObject) {
+			return GSON.fromJson(jsonObject, DidChangeWatchedFilesRegistrationOptions.class);
+		}
 		return null;
 	}