Fixes #61296: Ensure getWordAtPosition returns a word that touches the original passed in position

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

@@ -2004,7 +2004,8 @@ export class TextModel extends Disposable implements model.ITextModel {
 			lineContent.substring(rbStartOffset, rbEndOffset),
 			rbStartOffset
 		);
-		if (rightBiasedWord) {
+		// Make sure the result touches the original passed in position
+		if (rightBiasedWord && rightBiasedWord.startColumn <= _position.column && _position.column <= rightBiasedWord.endColumn) {
 			return rightBiasedWord;
 		}
 
@@ -2018,7 +2019,8 @@ export class TextModel extends Disposable implements model.ITextModel {
 				lineContent.substring(lbStartOffset, lbEndOffset),
 				lbStartOffset
 			);
-			if (leftBiasedWord) {
+			// Make sure the result touches the original passed in position
+			if (leftBiasedWord && leftBiasedWord.startColumn <= _position.column && _position.column <= leftBiasedWord.endColumn) {
 				return leftBiasedWord;
 			}
 		}

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

@@ -462,4 +462,30 @@ suite('Editor Model - Words', () => {
 		assert.deepEqual(model.getWordAtPosition(new Position(1, 6)), { word: 'xx', startColumn: 4, endColumn: 6 });
 		assert.deepEqual(model.getWordAtPosition(new Position(1, 7)), { word: 'ab', startColumn: 7, endColumn: 9 });
 	});
+
+	test('issue #61296: VS code freezes when editing CSS file with emoji', () => {
+		const MODE_ID = new LanguageIdentifier('testMode', 4);
+
+		const mode = new class extends MockMode {
+			constructor() {
+				super(MODE_ID);
+				this._register(LanguageConfigurationRegistry.register(this.getLanguageIdentifier(), {
+					wordPattern: /(#?-?\d*\.\d\w*%?)|(::?[\w-]*(?=[^,{;]*[,{]))|(([@#.!])?[\w-?]+%?|[@#!.])/g
+				}));
+			}
+		};
+		disposables.push(mode);
+
+		const thisModel = TextModel.createFromString('.🐷-a-b', undefined, MODE_ID);
+		disposables.push(thisModel);
+
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 1)), { word: '.', startColumn: 1, endColumn: 2 });
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 2)), { word: '.', startColumn: 1, endColumn: 2 });
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 3)), null);
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 4)), { word: '-a-b', startColumn: 4, endColumn: 8 });
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 5)), { word: '-a-b', startColumn: 4, endColumn: 8 });
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 6)), { word: '-a-b', startColumn: 4, endColumn: 8 });
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 7)), { word: '-a-b', startColumn: 4, endColumn: 8 });
+		assert.deepEqual(thisModel.getWordAtPosition(new Position(1, 8)), { word: '-a-b', startColumn: 4, endColumn: 8 });
+	});
 });

src/vs/workbench/parts/snippets/test/electron-browser/snippetsService.test.ts

@@ -11,6 +11,7 @@ import { ModeServiceImpl } from 'vs/editor/common/services/modeServiceImpl';
 import { TextModel } from 'vs/editor/common/model/textModel';
 import { ISnippetsService } from 'vs/workbench/parts/snippets/electron-browser/snippets.contribution';
 import { Snippet, SnippetSource } from 'vs/workbench/parts/snippets/electron-browser/snippetsFile';
+import { LanguageConfigurationRegistry } from 'vs/editor/common/modes/languageConfigurationRegistry';
 
 class SimpleSnippetService implements ISnippetsService {
 	_serviceBrand: any;
@@ -327,4 +328,28 @@ suite('SnippetsService', function () {
 
 		assert.equal(result.suggestions.length, 1);
 	});
+
+	test('issue #61296: VS code freezes when editing CSS file with emoji', async function () {
+		let toDispose = LanguageConfigurationRegistry.register(modeService.getLanguageIdentifier('fooLang'), {
+			wordPattern: /(#?-?\d*\.\d\w*%?)|(::?[\w-]*(?=[^,{;]*[,{]))|(([@#.!])?[\w-?]+%?|[@#!.])/g
+		});
+		snippetService = new SimpleSnippetService([new Snippet(
+			['fooLang'],
+			'bug',
+			'-a-bug',
+			'',
+			'second',
+			'',
+			SnippetSource.User
+		)]);
+
+		const provider = new SnippetCompletionProvider(modeService, snippetService);
+
+		let model = TextModel.createFromString('.🐷-a-b', undefined, modeService.getLanguageIdentifier('fooLang'));
+		let result = await provider.provideCompletionItems(model, new Position(1, 8));
+
+		assert.equal(result.suggestions.length, 1);
+
+		toDispose.dispose();
+	});
 });