Wait a bit after change before sending diagnostics

Fixes eclipse-lemminx#1162

Signed-off-by: azerr <azerr@redhat.com>

org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/XMLTextDocumentService.java

@@ -36,6 +36,7 @@
 import org.eclipse.lemminx.client.LimitFeature;
 import org.eclipse.lemminx.commons.ModelTextDocument;
 import org.eclipse.lemminx.commons.ModelTextDocuments;
+import org.eclipse.lemminx.commons.ModelValidatorDelayer;
 import org.eclipse.lemminx.commons.TextDocument;
 import org.eclipse.lemminx.commons.TextDocuments;
 import org.eclipse.lemminx.dom.DOMDocument;
@@ -114,6 +115,8 @@ public class XMLTextDocumentService implements TextDocumentService {
 
 	private final XMLLanguageServer xmlLanguageServer;
 	private final TextDocuments<ModelTextDocument<DOMDocument>> documents;
+	private final ModelValidatorDelayer<DOMDocument> xmlValidatorDelayer;
+
 	private SharedSettings sharedSettings;
 	private LimitExceededWarner limitExceededWarner;
 
@@ -165,7 +168,6 @@ public void triggerValidationIfNeeded() {
 		}
 	}
 
-	final ScheduledExecutorService delayer = Executors.newScheduledThreadPool(2);
 	private boolean codeActionLiteralSupport;
 	private boolean hierarchicalDocumentSymbolSupport;
 	private boolean definitionLinkSupport;
@@ -179,6 +181,11 @@ public XMLTextDocumentService(XMLLanguageServer xmlLanguageServer) {
 		});
 		this.sharedSettings = new SharedSettings();
 		this.limitExceededWarner = null;
+
+		ScheduledExecutorService delayer = Executors.newScheduledThreadPool(2);
+		this.xmlValidatorDelayer = new ModelValidatorDelayer<DOMDocument>(delayer, (document) -> {
+			validate(document, Collections.emptyMap());
+		});
 	}
 
 	public void updateClientCapabilities(ClientCapabilities capabilities,
@@ -568,7 +575,7 @@ private void triggerValidationFor(Collection<ModelTextDocument<DOMDocument>> doc
 			xmlLanguageServer.schedule(() -> {
 				documents.forEach(document -> {
 					try {
-						validate(document.getModel().getNow(null));
+						validate(document.getModel().getNow(null), false);
 					} catch (CancellationException e) {
 						// Ignore the error and continue to validate other documents
 					}
@@ -587,7 +594,11 @@ private void triggerValidationFor(TextDocument document, TriggeredBy triggeredBy
 		((ModelTextDocument<DOMDocument>) document).getModel()//
 				.thenAcceptAsync(xmlDocument -> {
 					// Validate the DOM document
-					validate(xmlDocument);
+					// When validation is triggered by a didChange, we process the validation with
+					// delay to avoid
+					// reporting to many 'textDocument/publishDiagnostics' notifications on client
+					// side.
+					validate(xmlDocument, triggeredBy == TriggeredBy.didChange);
 					// Manage didOpen, didChange document lifecycle participants
 					switch (triggeredBy) {
 					case didOpen:
@@ -624,8 +635,12 @@ private void triggerValidationFor(TextDocument document, TriggeredBy triggeredBy
 	 * @throws CancellationException when the DOM document content changed and
 	 *                               diagnostics must be stopped.
 	 */
-	void validate(DOMDocument xmlDocument) throws CancellationException {
-		validate(xmlDocument, Collections.emptyMap());
+	void validate(DOMDocument xmlDocument, boolean withDelay) throws CancellationException {
+		if (withDelay) {
+			xmlValidatorDelayer.validateWithDelay(xmlDocument.getDocumentURI(), xmlDocument);
+		} else {
+			validate(xmlDocument, Collections.emptyMap());
+		}
 	}
 
 	/**

org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/commons/ModelValidatorDelayer.java

@@ -0,0 +1,81 @@
+/*******************************************************************************
+* Copyright (c) 2022 Red Hat Inc. and others.
+* All rights reserved. This program and the accompanying materials
+* which accompanies this distribution, and is available at
+* http://www.eclipse.org/legal/epl-v20.html
+*
+* SPDX-License-Identifier: EPL-2.0
+*
+* Contributors:
+*     Red Hat Inc. - initial API and implementation
+*******************************************************************************/
+package org.eclipse.lemminx.commons;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+
+/**
+ * Validate a given model document with delay.
+ * 
+ * @author Angelo ZERR
+ *
+ * @param <T>
+ */
+public class ModelValidatorDelayer<T> {
+
+	private static final long DEFAULT_VALIDATION_DELAY_MS = 200;
+
+	private final ScheduledExecutorService executorService;
+
+	private final Consumer<T> validator;
+
+	private final Map<String, Future<?>> pendingValidationRequests;
+
+	private final long validationDelayMs;
+
+	public ModelValidatorDelayer(ScheduledExecutorService executorService, Consumer<T> validator) {
+		this(executorService, validator, DEFAULT_VALIDATION_DELAY_MS);
+	}
+
+	public ModelValidatorDelayer(ScheduledExecutorService executorService, Consumer<T> validator,
+			long validationDelayMs) {
+		this.executorService = executorService;
+		this.validator = validator;
+		this.pendingValidationRequests = new HashMap<>();
+		this.validationDelayMs = validationDelayMs;
+	}
+
+	/**
+	 * Validate the given model <code>document</code> identified by the given
+	 * <code>uri</code> with a delay.
+	 * 
+	 * @param uri      the document URI.
+	 * @param document the document model to validate.
+	 */
+	public void validateWithDelay(String uri, T document) {
+		cleanPendingValidation(uri);
+		Future<?> request = executorService.schedule(() -> {
+			synchronized (pendingValidationRequests) {
+				pendingValidationRequests.remove(uri);
+			}
+			validator.accept(document);
+		}, validationDelayMs, TimeUnit.MILLISECONDS);
+		synchronized (pendingValidationRequests) {
+			pendingValidationRequests.put(uri, request);
+		}
+	}
+
+	private void cleanPendingValidation(String uri) {
+		synchronized (pendingValidationRequests) {
+			Future<?> request = pendingValidationRequests.get(uri);
+			if (request != null) {
+				request.cancel(true);
+				pendingValidationRequests.remove(uri);
+			}
+		}
+	}
+}