Do not emit events when deltaDecorations is a no-op

src/vs/editor/common/model/textModelWithDecorations.ts

@@ -166,6 +166,10 @@ export class TextModelWithDecorations extends TextModelWithTokens implements edi
 				this._deltaDecorationsImpl(ownerId, [id], []);
 			},
 			deltaDecorations: (oldDecorations: string[], newDecorations: editorCommon.IModelDeltaDecoration[]): string[] => {
+				if (oldDecorations.length === 0 && newDecorations.length === 0) {
+					// nothing to do
+					return [];
+				}
 				this._currentDecorationsTrackerDidChange = true;
 				return this._deltaDecorationsImpl(ownerId, oldDecorations, newDecorations);
 			}
@@ -189,6 +193,10 @@ export class TextModelWithDecorations extends TextModelWithTokens implements edi
 		if (!oldDecorations) {
 			oldDecorations = [];
 		}
+		if (oldDecorations.length === 0 && newDecorations.length === 0) {
+			// nothing to do
+			return [];
+		}
 
 		try {
 			this._eventEmitter.beginDeferredEmit();

src/vs/editor/test/common/model/modelDecorations.test.ts

@@ -249,6 +249,21 @@ suite('Editor Model - Model Decorations', () => {
 		assert.equal(listenerCalled, 1, 'listener called');
 	});
 
+	test('decorations do not emit event on no-op deltaDecorations', () => {
+		let listenerCalled = 0;
+
+		thisModel.onDidChangeDecorations((e) => {
+			listenerCalled++;
+		});
+
+		thisModel.deltaDecorations([], []);
+		thisModel.changeDecorations((accessor) => {
+			accessor.deltaDecorations([], []);
+		});
+
+		assert.equal(listenerCalled, 0, 'listener not called');
+	});
+
 	// --------- editing text & effects on decorations
 
 	test('decorations are updated when inserting one line text before it', () => {