Add preference option for non-buffered file handling in Xtext editors.

see #1500

Author: raghucssit

org.eclipse.lsp4e/src/org/eclipse/lsp4e/LSPEclipseUtils.java

@@ -1642,6 +1642,6 @@ public static boolean isReadOnly(final IResource resource) {
 
 	private static boolean isNonBufferedFileHandlingEnabled() {
 		IPreferenceStore store = LanguageServerPlugin.getDefault().getPreferenceStore();
-		return store.getBoolean("org.eclipse.lsp4e.resourceFallback.enabled"); //$NON-NLS-1$
+		return store.getBoolean(LanguageServerWrapper.LSP4E_RESOURCE_FALLBACK_ENABLED_PREF_KEY);
 	}
 }

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

@@ -1663,6 +1663,8 @@ private static String getThrowableMessage(Throwable throwable) {
 	// Preference key: org.eclipse.lsp4e.resourceFallback.enabled (boolean). Default: false
 	private final boolean resourceFallbackEnabled;
 
+	public static final String LSP4E_RESOURCE_FALLBACK_ENABLED_PREF_KEY = "org.eclipse.lsp4e.resourceFallback.enabled"; //$NON-NLS-1$
+
 	/**
 	 * Listener that translates workspace resource changes into LSP file-level
 	 * events for files that are not backed by file buffers(Ex. Xtext Documents) and
@@ -1794,6 +1796,6 @@ private void handlePreChangeEvent(IResourceChangeEvent event) {
 
 	private boolean isNonBufferedFileListenerEnabled() {
 		IPreferenceStore store = LanguageServerPlugin.getDefault().getPreferenceStore();
-		return store.getBoolean("org.eclipse.lsp4e.resourceFallback.enabled"); //$NON-NLS-1$
+		return store.getBoolean(LSP4E_RESOURCE_FALLBACK_ENABLED_PREF_KEY);
 	}
 }

org.eclipse.lsp4e/src/org/eclipse/lsp4e/ui/LanguageServerPreferencePage.java

@@ -19,7 +19,9 @@
 import org.eclipse.jdt.annotation.Nullable;
 import org.eclipse.jface.action.Action;
 import org.eclipse.jface.dialogs.IDialogConstants;
+import org.eclipse.jface.dialogs.MessageDialog;
 import org.eclipse.jface.layout.GridDataFactory;
+import org.eclipse.jface.preference.IPreferenceStore;
 import org.eclipse.jface.preference.PreferencePage;
 import org.eclipse.jface.viewers.ArrayContentProvider;
 import org.eclipse.jface.viewers.CheckboxTableViewer;
@@ -33,6 +35,8 @@
 import org.eclipse.jface.viewers.ViewerComparator;
 import org.eclipse.lsp4e.ContentTypeToLSPLaunchConfigEntry;
 import org.eclipse.lsp4e.ContentTypeToLanguageServerDefinition;
+import org.eclipse.lsp4e.LanguageServerPlugin;
+import org.eclipse.lsp4e.LanguageServerWrapper;
 import org.eclipse.lsp4e.LanguageServersRegistry;
 import org.eclipse.lsp4e.enablement.EnablementTester;
 import org.eclipse.swt.SWT;
@@ -56,6 +60,7 @@ public class LanguageServerPreferencePage extends PreferencePage implements IWor
 	private final LanguageServersRegistry registry = LanguageServersRegistry.getInstance();
 	private List<ContentTypeToLSPLaunchConfigEntry> workingCopy = lateNonNull();
 	private Button removeButton = lateNonNull();
+	private Button resourceFallbackCheckbox = lateNonNull();
 	private CheckboxTableViewer checkboxViewer = lateNonNull();
 	private TableViewer viewer = lateNonNull();
 	private final SelectionAdapter contentTypeLinkListener;
@@ -174,6 +179,15 @@ public void widgetSelected(SelectionEvent e) {
 		viewer.addSelectionChangedListener(event -> updateButtons());
 		viewer.setInput(workingCopy);
 		updateButtons();
+
+		// non-buffered file handling for Xtext like editors.
+		resourceFallbackCheckbox = new Button(res, SWT.CHECK);
+		GridDataFactory.swtDefaults().align(SWT.FILL, SWT.CENTER).span(2, 1).applyTo(resourceFallbackCheckbox);
+		resourceFallbackCheckbox.setText(Messages.non_buffered_file_support);
+		IPreferenceStore store = LanguageServerPlugin.getDefault().getPreferenceStore();
+		boolean enabled = store.getBoolean(LanguageServerWrapper.LSP4E_RESOURCE_FALLBACK_ENABLED_PREF_KEY);
+		resourceFallbackCheckbox.setSelection(enabled);
+
 		return res;
 	}
 
@@ -296,6 +310,17 @@ public boolean performOk() {
 		this.registry.setAssociations(this.workingCopy);
 		final var enableDisableLSJob = new EnableDisableLSJob(changedDefinitions, getEditors());
 		enableDisableLSJob.schedule();
+
+		IPreferenceStore store = LanguageServerPlugin.getDefault().getPreferenceStore();
+		boolean oldValue = store.getBoolean(LanguageServerWrapper.LSP4E_RESOURCE_FALLBACK_ENABLED_PREF_KEY);
+		boolean newValue = resourceFallbackCheckbox.getSelection();
+		store.setValue(LanguageServerWrapper.LSP4E_RESOURCE_FALLBACK_ENABLED_PREF_KEY, newValue);
+		if (oldValue != newValue) {
+			var shell = getShell();
+			String title = Messages.PreferencesPage_nonBufferedFileSupportRestartTitle;
+			String msg = Messages.PreferencesPage_nonBufferedFileSupportWarningMessage;
+			MessageDialog.openWarning(shell, title, msg);
+		}
 		return super.performOk();
 	}
 

org.eclipse.lsp4e/src/org/eclipse/lsp4e/ui/Messages.java

@@ -106,6 +106,9 @@ public final class Messages extends NLS {
 	public static String TH_diplay_hint;
 	public static String TH_cannot_find_file;
 	public static String occurrences;
+	public static String non_buffered_file_support;
+	public static String PreferencesPage_nonBufferedFileSupportRestartTitle;
+	public static String PreferencesPage_nonBufferedFileSupportWarningMessage;
 
 	static {
 		NLS.initializeMessages("org.eclipse.lsp4e.ui.messages", Messages.class); //$NON-NLS-1$

org.eclipse.lsp4e/src/org/eclipse/lsp4e/ui/messages.properties

@@ -44,6 +44,9 @@ PreferencesPage_restartWarning_restart=Restart Now
 PreferencesPage_enableOnTypeFormatting=Enable on type formatting
 NewContentTypeLSPLaunchDialog_associateContentType=Associate content-type...
 NewContentTypeLSPLaunchDialog_withLSPLaunch=...with Language Server Launch Configuration
+non_buffered_file_support=Enable non-buffered file handling (support for Xtext-like editors)
+PreferencesPage_nonBufferedFileSupportRestartTitle=Non-buffered File Support Restart Required
+PreferencesPage_nonBufferedFileSupportWarningMessage=Change in non-buffered file support may require a restart of all opened editors to take effect.
 
 codeActions_description=Code Actions from language server.
 codeActions_label=Code Actions