Add check if WorkspaceFolders are supported or not

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/CommandServiceTest.java

@@ -76,6 +76,7 @@ public void testExecute() throws Exception {
 		initialize((InitializeParams it) -> {
 			ClientCapabilities clientCapabilities = new ClientCapabilities();
 			WorkspaceClientCapabilities workspaceClientCapabilities = new WorkspaceClientCapabilities();
+			workspaceClientCapabilities.setWorkspaceFolders(true);
 			workspaceClientCapabilities.setExecuteCommand(new ExecuteCommandCapabilities(true));
 			clientCapabilities.setWorkspace(workspaceClientCapabilities);
 			it.setCapabilities(clientCapabilities);

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/HierarchicalDocumentSymbolTest.java

@@ -12,13 +12,17 @@
 import org.eclipse.lsp4j.DocumentSymbolCapabilities;
 import org.eclipse.lsp4j.InitializeParams;
 import org.eclipse.lsp4j.TextDocumentClientCapabilities;
+import org.eclipse.lsp4j.WorkspaceClientCapabilities;
 import org.eclipse.xtext.testing.DocumentSymbolConfiguration;
 import org.eclipse.xtext.xbase.lib.Procedures.Procedure1;
 import org.junit.Test;
 
 public class HierarchicalDocumentSymbolTest extends AbstractTestLangLanguageServerTest {
 	private static final Procedure1<? super InitializeParams> INITIALIZER = (InitializeParams it) -> {
 		ClientCapabilities clientCapabilities = new ClientCapabilities();
+		WorkspaceClientCapabilities workspaceClientCapabilities = new WorkspaceClientCapabilities();
+		workspaceClientCapabilities.setWorkspaceFolders(true);
+		clientCapabilities.setWorkspace(workspaceClientCapabilities);
 		DocumentSymbolCapabilities documentSymbolCapabilities = new DocumentSymbolCapabilities();
 		documentSymbolCapabilities.setHierarchicalDocumentSymbolSupport(true);
 		TextDocumentClientCapabilities textDocumentClientCapabilities = new TextDocumentClientCapabilities();

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/PrepareRenameTest.java

@@ -210,6 +210,7 @@ private InitializeResult initializeWithPrepareSupport() {
 		return super.initialize((InitializeParams params) -> {
 			ClientCapabilities clientCapabilities = new ClientCapabilities();
 			WorkspaceClientCapabilities workspaceClientCapabilities = new WorkspaceClientCapabilities();
+			workspaceClientCapabilities.setWorkspaceFolders(true);
 			clientCapabilities.setWorkspace(workspaceClientCapabilities);
 			TextDocumentClientCapabilities textDocumentClientCapabilities = new TextDocumentClientCapabilities();
 			textDocumentClientCapabilities.setRename(new RenameCapabilities(true, false));

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/Rename2Test.java

@@ -97,6 +97,7 @@ protected InitializeResult initialize() {
 		return super.initialize((InitializeParams params) -> {
 			ClientCapabilities clientCapabilities = new ClientCapabilities();
 			WorkspaceClientCapabilities workspaceClientCapabilities = new WorkspaceClientCapabilities();
+			workspaceClientCapabilities.setWorkspaceFolders(true);
 			WorkspaceEditCapabilities workspaceEditCapabilities = new WorkspaceEditCapabilities();
 			workspaceEditCapabilities.setDocumentChanges(true);
 			workspaceClientCapabilities.setWorkspaceEdit(workspaceEditCapabilities);

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/Rename3Test.java

@@ -134,6 +134,7 @@ protected InitializeResult initialize() {
 		return super.initialize((InitializeParams params) -> {
 			ClientCapabilities clientCapabilities = new ClientCapabilities();
 			WorkspaceClientCapabilities workspaceClientCapabilities = new WorkspaceClientCapabilities();
+			workspaceClientCapabilities.setWorkspaceFolders(true);
 			WorkspaceEditCapabilities workspaceEditCapabilities = new WorkspaceEditCapabilities();
 			workspaceEditCapabilities.setDocumentChanges(true);
 			workspaceClientCapabilities.setWorkspaceEdit(workspaceEditCapabilities);

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/RenamePositionTest.java

@@ -19,6 +19,7 @@
 import org.eclipse.lsp4j.RenameParams;
 import org.eclipse.lsp4j.TextDocumentClientCapabilities;
 import org.eclipse.lsp4j.TextDocumentIdentifier;
+import org.eclipse.lsp4j.WorkspaceClientCapabilities;
 import org.eclipse.lsp4j.WorkspaceEdit;
 import org.eclipse.lsp4j.jsonrpc.ResponseErrorException;
 import org.eclipse.lsp4j.jsonrpc.messages.Either3;
@@ -103,6 +104,9 @@ protected void renameWithSuccess(String model, Position position) throws Excepti
 		String modelFile = writeFile("MyType.testlang", model);
 		initialize((InitializeParams params) -> {
 			ClientCapabilities clientCapabilities = new ClientCapabilities();
+			WorkspaceClientCapabilities workspaceCapabilities = new WorkspaceClientCapabilities();
+			workspaceCapabilities.setWorkspaceFolders(true);
+			clientCapabilities.setWorkspace(workspaceCapabilities);
 			TextDocumentClientCapabilities textDocumentClientCapabilities = new TextDocumentClientCapabilities();
 			textDocumentClientCapabilities.setRename(new RenameCapabilities(true, false));
 			clientCapabilities.setTextDocument(textDocumentClientCapabilities);

org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/WorkspaceFoldersTest.java

@@ -13,8 +13,12 @@
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
+import org.eclipse.lsp4j.ClientCapabilities;
 import org.eclipse.lsp4j.DidChangeWorkspaceFoldersParams;
 import org.eclipse.lsp4j.InitializeParams;
+import org.eclipse.lsp4j.InitializeResult;
+import org.eclipse.lsp4j.NotebookDocumentChangeEvent;
+import org.eclipse.lsp4j.WorkspaceClientCapabilities;
 import org.eclipse.lsp4j.WorkspaceFolder;
 import org.eclipse.lsp4j.WorkspaceFoldersChangeEvent;
 import org.eclipse.xtext.ide.server.ILanguageServerAccess;
@@ -47,16 +51,34 @@ public class WorkspaceFoldersTest extends AbstractTestLangLanguageServerTest {
 	public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
 	@Test
-	public void testInitialize() throws Exception {
+	public void testInitializeWithoutWorkspaceFolders() throws Exception {
+		File rootFolder1 = temporaryFolder.newFolder("root1");
+		String oneUri = writeFile(rootFolder1, "one.testlang", "type Foo { Bar bar }");
+		InitializeResult capabilities = initialize((InitializeParams it) -> {
+			it.setRootPath(rootFolder1.getPath());
+		}, true, true);
+		Assert.assertNull(capabilities.getCapabilities().getWorkspace());
+		Assert.assertEquals(1, getDiagnostics().size());
+		Assert.assertEquals(1, getDiagnostics().get(oneUri).size());
+	}
+
+	@Test
+	public void testInitializeWithWorkspaceFolders() throws Exception {
 		File rootFolder1 = temporaryFolder.newFolder("root1");
 		File rootFolder2 = temporaryFolder.newFolder("root2");
 		writeFile(rootFolder1, "one.testlang", "type Foo { Bar bar }");
 		String twoUri = writeFile(rootFolder2, "two.testlang", "type Bar { Foo foo }");
-		initialize((InitializeParams it) -> {
+		InitializeResult capabilities = initialize((InitializeParams it) -> {
+			ClientCapabilities clientCapabilities = new ClientCapabilities();
+			WorkspaceClientCapabilities workspaceClientCapabilities = new WorkspaceClientCapabilities();
+			workspaceClientCapabilities.setWorkspaceFolders(true);
+			clientCapabilities.setWorkspace(workspaceClientCapabilities);
+			it.setCapabilities(clientCapabilities);
 			it.setWorkspaceFolders(
 					Lists.newArrayList(new WorkspaceFolder(uriExtensions.toUriString(rootFolder1.toURI()), "root1"),
 							new WorkspaceFolder(uriExtensions.toUriString(rootFolder2.toURI()), "root2")));
 		});
+		Assert.assertEquals(true, capabilities.getCapabilities().getWorkspace().getWorkspaceFolders().getSupported());
 		Assert.assertEquals(2, getDiagnostics().size());
 		Assert.assertEquals(1, getDiagnostics().get(twoUri).size());
 		withBuild(() -> {

org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/LanguageServerImpl.java

@@ -221,7 +221,6 @@ public CompletableFuture<InitializeResult> initialize(InitializeParams params) {
 		if (initializeParams != null) {
 			throw new IllegalStateException("This language server has already been initialized.");
 		}
-		URI baseDir = getBaseDir(params);
 		if (languagesRegistry.getExtensionToFactoryMap().isEmpty()) {
 			throw new IllegalStateException(
 					"No Xtext languages have been registered. Please make sure you have added the languages\'s setup class in \'/META-INF/services/org.eclipse.xtext.ISetup\'");
@@ -233,18 +232,25 @@ public CompletableFuture<InitializeResult> initialize(InitializeParams params) {
 		result.setCapabilities(createServerCapabilities(params));
 		access.addBuildListener(this);
 		return requestManager.runWrite(() -> {
-			if (workspaceManager.isSupportsWorkspaceFolders()) {
+			if (clientSupportsWorkspaceFolders() && workspaceManager.isSupportsWorkspaceFolders()) {
 				List<WorkspaceFolder> workspaceFolders = params.getWorkspaceFolders();
 				if (workspaceFolders == null)
 					workspaceFolders = Collections.emptyList();
 				workspaceManager.initialize(workspaceFolders, this::publishDiagnostics, CancelIndicator.NullImpl);
 			} else {
+				URI baseDir = getBaseDir(params);
 				workspaceManager.initialize(baseDir, this::publishDiagnostics, CancelIndicator.NullImpl);
 			}
 			return result;
 		}, (cancelIndicator, it) -> it).thenApply(it -> initializeResult = it);
 	}
 
+	protected boolean clientSupportsWorkspaceFolders() {
+		return this.initializeParams.getCapabilities() != null 
+				&& this.initializeParams.getCapabilities().getWorkspace() != null 
+				&& Objects.equal(this.initializeParams.getCapabilities().getWorkspace().getWorkspaceFolders(), Boolean.TRUE);
+	}
+
 	/**
 	 * Configure the server capabilities for this instance.
 	 *

org.eclipse.xtext.testing/src/org/eclipse/xtext/testing/AbstractLanguageServerTest.xtend

@@ -95,6 +95,8 @@ import static extension org.eclipse.xtext.util.Strings.*
 import org.eclipse.lsp4j.WorkspaceSymbol
 import org.eclipse.lsp4j.SemanticTokensParams
 import com.google.common.annotations.Beta
+import org.eclipse.lsp4j.ClientCapabilities
+import org.eclipse.lsp4j.WorkspaceClientCapabilities
 
 /**
  * @author Sven Efftinge - Initial contribution and API
@@ -217,17 +219,30 @@ abstract class AbstractLanguageServerTest implements Endpoint {
 	}
 
 	protected def InitializeResult initialize((InitializeParams)=>void initializer, boolean callInitialized) {
+		initialize(initializer, callInitialized, false)
+	}
+
+	protected def InitializeResult initialize((InitializeParams)=>void initializer, boolean callInitialized, boolean useRootPath) {
 		val params = new InitializeParams => [
 			processId = 1
 			workspaceFolders = #[
 				new WorkspaceFolder(root.toURI.normalize.toUriString, '')
 			]
 		]
+		if (!useRootPath) {
+			if (params.capabilities === null) {
+				params.capabilities = new ClientCapabilities
+			}
+			if (params.capabilities.workspace === null) {
+				params.capabilities.workspace = new WorkspaceClientCapabilities
+			}
+			params.capabilities.workspace.workspaceFolders = true
+		}
 		initializer?.apply(params)
 		hierarchicalDocumentSymbolSupport = params.capabilities?.textDocument?.documentSymbol?.
 			hierarchicalDocumentSymbolSupport ?: false;
 		val result = languageServer.initialize(params).get
-		if(callInitialized)
+		if (callInitialized)
 			languageServer.initialized(null)
 		return result
 	}

org.eclipse.xtext.testing/xtend-gen/org/eclipse/xtext/testing/AbstractLanguageServerTest.java

@@ -82,6 +82,7 @@
 import org.eclipse.lsp4j.TextDocumentItem;
 import org.eclipse.lsp4j.TextEdit;
 import org.eclipse.lsp4j.VersionedTextDocumentIdentifier;
+import org.eclipse.lsp4j.WorkspaceClientCapabilities;
 import org.eclipse.lsp4j.WorkspaceEdit;
 import org.eclipse.lsp4j.WorkspaceFolder;
 import org.eclipse.lsp4j.WorkspaceSymbol;
@@ -333,6 +334,10 @@ protected InitializeResult initialize(final Procedure1<? super InitializeParams>
   }
 
   protected InitializeResult initialize(final Procedure1<? super InitializeParams> initializer, final boolean callInitialized) {
+    return this.initialize(initializer, callInitialized, false);
+  }
+
+  protected InitializeResult initialize(final Procedure1<? super InitializeParams> initializer, final boolean callInitialized, final boolean useRootPath) {
     try {
       InitializeParams _initializeParams = new InitializeParams();
       final Procedure1<InitializeParams> _function = (InitializeParams it) -> {
@@ -342,14 +347,31 @@ protected InitializeResult initialize(final Procedure1<? super InitializeParams>
         it.setWorkspaceFolders(Collections.<WorkspaceFolder>unmodifiableList(CollectionLiterals.<WorkspaceFolder>newArrayList(_workspaceFolder)));
       };
       final InitializeParams params = ObjectExtensions.<InitializeParams>operator_doubleArrow(_initializeParams, _function);
+      if ((!useRootPath)) {
+        ClientCapabilities _capabilities = params.getCapabilities();
+        boolean _tripleEquals = (_capabilities == null);
+        if (_tripleEquals) {
+          ClientCapabilities _clientCapabilities = new ClientCapabilities();
+          params.setCapabilities(_clientCapabilities);
+        }
+        WorkspaceClientCapabilities _workspace = params.getCapabilities().getWorkspace();
+        boolean _tripleEquals_1 = (_workspace == null);
+        if (_tripleEquals_1) {
+          ClientCapabilities _capabilities_1 = params.getCapabilities();
+          WorkspaceClientCapabilities _workspaceClientCapabilities = new WorkspaceClientCapabilities();
+          _capabilities_1.setWorkspace(_workspaceClientCapabilities);
+        }
+        WorkspaceClientCapabilities _workspace_1 = params.getCapabilities().getWorkspace();
+        _workspace_1.setWorkspaceFolders(Boolean.valueOf(true));
+      }
       if (initializer!=null) {
         initializer.apply(params);
       }
       Boolean _elvis = null;
-      ClientCapabilities _capabilities = params.getCapabilities();
+      ClientCapabilities _capabilities_2 = params.getCapabilities();
       TextDocumentClientCapabilities _textDocument = null;
-      if (_capabilities!=null) {
-        _textDocument=_capabilities.getTextDocument();
+      if (_capabilities_2!=null) {
+        _textDocument=_capabilities_2.getTextDocument();
       }
       DocumentSymbolCapabilities _documentSymbol = null;
       if (_textDocument!=null) {