Fixes #10586: Avoid slow matching regex /[^\s]+$/

src/vs/editor/common/modes/snippetsRegistry.ts

@@ -102,12 +102,31 @@ class SnippetsRegistry implements ISnippetsRegistry {
 	}
 }
 
-export function getNonWhitespacePrefix(model: IReadOnlyModel, position: IPosition) : string {
+export interface ISimpleModel {
+	getLineContent(lineNumber): string;
+}
+
+export function getNonWhitespacePrefix(model: ISimpleModel, position: IPosition) : string {
+	/**
+	 * Do not analyze more characters
+	 */
+	const MAX_PREFIX_LENGTH = 100;
+
 	let line = model.getLineContent(position.lineNumber).substr(0, position.column - 1);
-	let match = line.match(/[^\s]+$/);
-	if (match) {
-		return match[0];
+
+	let minChIndex = Math.max(0, line.length - MAX_PREFIX_LENGTH);
+	for (let chIndex = line.length - 1; chIndex >= minChIndex; chIndex--) {
+		let ch = line.charAt(chIndex);
+
+		if (/\s/.test(ch)) {
+			return line.substr(chIndex + 1);
+		}
 	}
+
+	if (minChIndex === 0) {
+		return line;
+	}
+
 	return '';
 }
 

src/vs/editor/test/common/modes/snippetsRegistry.test.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+import * as assert from 'assert';
+import {getNonWhitespacePrefix} from 'vs/editor/common/modes/snippetsRegistry';
+
+suite('getNonWhitespacePrefix', () => {
+
+	function assertGetNonWhitespacePrefix(line:string, column:number, expected:string): void {
+		let model = {
+			getLineContent: (lineNumber:number) => line
+		};
+		let actual = getNonWhitespacePrefix(model, { lineNumber: 1, column: column });
+		assert.equal(actual, expected);
+	}
+
+	test('empty line', () => {
+		assertGetNonWhitespacePrefix('', 1, '');
+	});
+
+	test('singleWordLine', () => {
+		assertGetNonWhitespacePrefix('something',  1, '');
+		assertGetNonWhitespacePrefix('something',  2, 's');
+		assertGetNonWhitespacePrefix('something',  3, 'so');
+		assertGetNonWhitespacePrefix('something',  4, 'som');
+		assertGetNonWhitespacePrefix('something',  5, 'some');
+		assertGetNonWhitespacePrefix('something',  6, 'somet');
+		assertGetNonWhitespacePrefix('something',  7, 'someth');
+		assertGetNonWhitespacePrefix('something',  8, 'somethi');
+		assertGetNonWhitespacePrefix('something',  9, 'somethin');
+		assertGetNonWhitespacePrefix('something', 10, 'something');
+	});
+
+	test('two word line', () => {
+		assertGetNonWhitespacePrefix('something interesting',  1, '');
+		assertGetNonWhitespacePrefix('something interesting',  2, 's');
+		assertGetNonWhitespacePrefix('something interesting',  3, 'so');
+		assertGetNonWhitespacePrefix('something interesting',  4, 'som');
+		assertGetNonWhitespacePrefix('something interesting',  5, 'some');
+		assertGetNonWhitespacePrefix('something interesting',  6, 'somet');
+		assertGetNonWhitespacePrefix('something interesting',  7, 'someth');
+		assertGetNonWhitespacePrefix('something interesting',  8, 'somethi');
+		assertGetNonWhitespacePrefix('something interesting',  9, 'somethin');
+		assertGetNonWhitespacePrefix('something interesting', 10, 'something');
+		assertGetNonWhitespacePrefix('something interesting', 11, '');
+		assertGetNonWhitespacePrefix('something interesting', 12, 'i');
+		assertGetNonWhitespacePrefix('something interesting', 13, 'in');
+		assertGetNonWhitespacePrefix('something interesting', 14, 'int');
+		assertGetNonWhitespacePrefix('something interesting', 15, 'inte');
+		assertGetNonWhitespacePrefix('something interesting', 16, 'inter');
+		assertGetNonWhitespacePrefix('something interesting', 17, 'intere');
+		assertGetNonWhitespacePrefix('something interesting', 18, 'interes');
+		assertGetNonWhitespacePrefix('something interesting', 19, 'interest');
+		assertGetNonWhitespacePrefix('something interesting', 20, 'interesti');
+		assertGetNonWhitespacePrefix('something interesting', 21, 'interestin');
+		assertGetNonWhitespacePrefix('something interesting', 22, 'interesting');
+	});
+
+	test('many separators', () => {
+		// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions?redirectlocale=en-US&redirectslug=JavaScript%2FGuide%2FRegular_Expressions#special-white-space
+		// \s matches a single white space character, including space, tab, form feed, line feed.
+		// Equivalent to [ \f\n\r\t\v\u00a0\u1680\u180e\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff].
+
+		assertGetNonWhitespacePrefix('something interesting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\tinteresting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\finteresting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\vinteresting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\u00a0interesting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\u2000interesting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\u2028interesting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\u3000interesting', 22, 'interesting');
+		assertGetNonWhitespacePrefix('something\ufeffinteresting', 22, 'interesting');
+
+	});
+});