Basic support for onTypeFormatting (#1255)

Author: mickaelistria

org.eclipse.lsp4e/plugin.xml

@@ -926,5 +926,12 @@
             id="org.eclipse.lsp4e.pathParameterType"
             type="org.eclipse.core.runtime.IPath" />
    </extension>
+   <extension
+         point="org.eclipse.ui.genericeditor.autoEditStrategies">
+      <autoEditStrategy
+            class="org.eclipse.lsp4e.format.DocumentFormatOnTypeAutoEditStrategy"
+            contentType="org.eclipse.core.runtime.text">
+      </autoEditStrategy>
+   </extension>
 
 </plugin>

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

@@ -82,6 +82,7 @@
 import org.eclipse.lsp4j.CodeActionOptions;
 import org.eclipse.lsp4j.DidChangeWorkspaceFoldersParams;
 import org.eclipse.lsp4j.DocumentFormattingOptions;
+import org.eclipse.lsp4j.DocumentOnTypeFormattingOptions;
 import org.eclipse.lsp4j.DocumentRangeFormattingOptions;
 import org.eclipse.lsp4j.ExecuteCommandOptions;
 import org.eclipse.lsp4j.InitializeParams;
@@ -1040,6 +1041,11 @@ void registerCapability(RegistrationParams params) {
 				serverCapabilities.setTypeHierarchyProvider(Boolean.TRUE);
 				addRegistration(reg, () -> serverCapabilities.setTypeHierarchyProvider(typeHierarchyBeforeRegistration));
 				break;
+			case "textDocument/onTypeFormatting": //$NON-NLS-1$
+				final var onTypeFormattingBeforeRegistration = serverCapabilities.getDocumentOnTypeFormattingProvider();
+				serverCapabilities.setDocumentOnTypeFormattingProvider(reg.getRegisterOptions() instanceof DocumentOnTypeFormattingOptions opts ? opts : null);
+				addRegistration(reg, () -> serverCapabilities.setDocumentOnTypeFormattingProvider(onTypeFormattingBeforeRegistration));
+				break;
 		}});
 	}
 

org.eclipse.lsp4e/src/org/eclipse/lsp4e/format/DocumentFormatOnTypeAutoEditStrategy.java

@@ -0,0 +1,67 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Red Hat, Inc.
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package org.eclipse.lsp4e.format;
+
+import org.eclipse.jdt.annotation.Nullable;
+import org.eclipse.jface.text.BadLocationException;
+import org.eclipse.jface.text.DocumentCommand;
+import org.eclipse.jface.text.IAutoEditStrategy;
+import org.eclipse.jface.text.IDocument;
+import org.eclipse.lsp4e.LSPEclipseUtils;
+import org.eclipse.lsp4e.LanguageServerPlugin;
+import org.eclipse.lsp4e.LanguageServers;
+import org.eclipse.lsp4e.operations.format.LSPFormatter;
+import org.eclipse.lsp4j.DocumentOnTypeFormattingParams;
+import org.eclipse.lsp4j.FormattingOptions;
+import org.eclipse.lsp4j.TextDocumentIdentifier;
+import org.eclipse.lsp4j.jsonrpc.messages.Either;
+
+public class DocumentFormatOnTypeAutoEditStrategy implements IAutoEditStrategy {
+
+	@Override
+	public void customizeDocumentCommand(@Nullable IDocument document, @Nullable DocumentCommand command) {
+		if (document == null || command == null || command.getCommandCount() > 1 || command.text.isEmpty()) {
+			return;
+		}
+		var executor = LanguageServers.forDocument(document)
+			.withCapability(capabilities -> Either.forLeft(capabilities.getDocumentOnTypeFormattingProvider() != null
+				&& (command.text.equals(capabilities.getDocumentOnTypeFormattingProvider().getFirstTriggerCharacter()) ||
+					(capabilities.getDocumentOnTypeFormattingProvider().getMoreTriggerCharacter() != null && capabilities.getDocumentOnTypeFormattingProvider().getMoreTriggerCharacter().contains(command.text)))));
+		if (!executor.anyMatching()) {
+			return;
+		}
+		FormattingOptions formattingOptions = LSPFormatter.getFormatOptions();
+		TextDocumentIdentifier textDocumentIdentifier = LSPEclipseUtils.toTextDocumentIdentifier(document);
+		if (textDocumentIdentifier == null) {
+			return;
+		}
+		try {
+			DocumentOnTypeFormattingParams params = new DocumentOnTypeFormattingParams(textDocumentIdentifier, formattingOptions, LSPEclipseUtils.toPosition(command.offset, document), command.text);
+			executor.computeFirst(ls -> ls.getTextDocumentService().onTypeFormatting(params)).join()
+				.ifPresent(edits -> {
+					edits.forEach(edit -> {
+						try {
+							int fromOffset = LSPEclipseUtils.toOffset(edit.getRange().getStart(), document);
+							int toOffset = LSPEclipseUtils.toOffset(edit.getRange().getEnd(), document);
+							if (fromOffset == command.offset) {
+								command.text += edit.getNewText();
+							} else {
+								command.addCommand(fromOffset, toOffset - fromOffset, edit.getNewText(), null);
+							}
+						} catch (BadLocationException ex) {
+							LanguageServerPlugin.logError(ex);
+						}
+					});
+				});
+		} catch (BadLocationException e) {
+			LanguageServerPlugin.logError(e);
+		}
+	}
+
+}

org.eclipse.lsp4e/src/org/eclipse/lsp4e/internal/SupportedFeatures.java

@@ -42,6 +42,7 @@
 import org.eclipse.lsp4j.InlayHintCapabilities;
 import org.eclipse.lsp4j.InsertTextMode;
 import org.eclipse.lsp4j.MarkupKind;
+import org.eclipse.lsp4j.OnTypeFormattingCapabilities;
 import org.eclipse.lsp4j.PublishDiagnosticsCapabilities;
 import org.eclipse.lsp4j.RangeFormattingCapabilities;
 import org.eclipse.lsp4j.ReferencesCapabilities;
@@ -129,7 +130,7 @@ public static TextDocumentClientCapabilities getTextDocumentClientCapabilities()
 				MarkupKind.MARKDOWN, //
 				MarkupKind.PLAINTEXT));
 		textDocumentClientCapabilities.setHover(hoverCapabilities);
-		textDocumentClientCapabilities.setOnTypeFormatting(null); // TODO
+		textDocumentClientCapabilities.setOnTypeFormatting(new OnTypeFormattingCapabilities(true));
 		textDocumentClientCapabilities.setRangeFormatting(new RangeFormattingCapabilities());
 		textDocumentClientCapabilities.setReferences(new ReferencesCapabilities());
 		final var renameCapabilities = new RenameCapabilities();