Improve marker resolution performance

by not connecting the file where we retrieve marker information. That is
an unnecessary step which can be expensive (for example the Xtext
language server rebuilds the source) and causes timeouts on
checkMarkerResoultion

org.eclipse.lsp4e/src/org/eclipse/lsp4e/LanguageServiceAccessor.java

@@ -144,11 +144,20 @@ public boolean isActive() {
 
 	public static @NonNull List<CompletableFuture<LanguageServer>> getInitializedLanguageServers(@NonNull IFile file,
 			@Nullable Predicate<ServerCapabilities> request) throws IOException {
+			return getInitializedLanguageServers(file, request, true);
+	}
+
+	public static @NonNull List<CompletableFuture<LanguageServer>> getInitializedLanguageServers(@NonNull IFile file,
+			@Nullable Predicate<ServerCapabilities> request, boolean connectFile) throws IOException {
 		synchronized (startedServers) {
 			Collection<LanguageServerWrapper> wrappers = getLSWrappers(file, request);
 			return wrappers.stream().map(wrapper -> wrapper.getInitializedServer().thenApplyAsync(server -> {
 				try {
-					wrapper.connect(file, null);
+					if (connectFile) {
+						wrapper.connect(file, null);
+					} else {
+						wrapper.start();
+					}
 				} catch (IOException e) {
 					LanguageServerPlugin.logError(e);
 				}
@@ -229,9 +238,30 @@ public static CompletableFuture<LanguageServer> getInitializedLanguageServer(@No
 			@NonNull LanguageServerDefinition lsDefinition,
 			Predicate<ServerCapabilities> capabilitiesPredicate)
 			throws IOException {
+		return getInitializedLanguageServer(file, lsDefinition, capabilitiesPredicate, true);
+	}
+
+	/**
+	 * Get the requested language server instance for the given file. Starts the language server if not already started.
+	 * @param file
+	 * @param lsDefinition
+	 * @param capabilitiesPredicate a predicate to check capabilities
+	 * @param connectFile if the file should be connected
+	 * @return a LanguageServer for the given file, which is defined with provided server ID and conforms to specified request.
+	 *  If {@code capabilitesPredicate} does not test positive for the server's capabilities, {@code null} is returned.
+	 */
+	public static CompletableFuture<LanguageServer> getInitializedLanguageServer(@NonNull IFile file,
+			@NonNull LanguageServerDefinition lsDefinition,
+			Predicate<ServerCapabilities> capabilitiesPredicate,
+			boolean connectFile)
+			throws IOException {
 		LanguageServerWrapper wrapper = getLSWrapper(file.getProject(), lsDefinition, file.getFullPath());
 		if (capabilitiesComply(wrapper, capabilitiesPredicate)) {
-			wrapper.connect(file, null);
+			if (connectFile) {
+				wrapper.connect(file, null);
+			} else {
+				wrapper.start();
+			}
 			return wrapper.getInitializedServer();
 		}
 		return null;

org.eclipse.lsp4e/src/org/eclipse/lsp4e/operations/codeactions/LSPCodeActionMarkerResolution.java

@@ -155,7 +155,7 @@ private List<CompletableFuture<LanguageServer>> getLanguageServerFutures(@NonNul
 				CompletableFuture<LanguageServer> serverFuture = LanguageServiceAccessor
 						.getInitializedLanguageServer(file, definition,
 								serverCapabilities -> serverCapabilities == null
-										|| providesCodeActions(serverCapabilities));
+										|| providesCodeActions(serverCapabilities), false);
 				if (serverFuture != null) {
 					languageServerFutures.add(serverFuture);
 				}
@@ -174,7 +174,7 @@ private List<CompletableFuture<LanguageServer>> getLanguageServerFutures(@NonNul
 							return true;
 						}
 						return false;
-					}));
+					}, false));
 		}
 		return languageServerFutures;
 	}