Fixes #53899

src/vs/editor/common/controller/cursorWordOperations.ts

@@ -468,13 +468,31 @@ export class WordOperations {
 export function _lastWordPartEnd(str: string, startIndex: number = str.length - 1): number {
 	let ignoreUpperCase = !strings.isLowerAsciiLetter(str.charCodeAt(startIndex + 1));
 	for (let i = startIndex; i >= 0; i--) {
-		let chCode = str.charCodeAt(i);
-		if (chCode === CharCode.Space || chCode === CharCode.Tab || (!ignoreUpperCase && strings.isUpperAsciiLetter(chCode)) || chCode === CharCode.Underline) {
+		const chCode = str.charCodeAt(i);
+		if (chCode === CharCode.Space || chCode === CharCode.Tab) {
+			if (i === 0) {
+				return 0;
+			}
+			const prevChCode = str.charCodeAt(i - 1);
+			if (prevChCode !== CharCode.Space && prevChCode !== CharCode.Tab) {
+				return i - 1;
+			}
+		}
+		if (!ignoreUpperCase && strings.isUpperAsciiLetter(chCode)) {
 			return i - 1;
 		}
 		if (ignoreUpperCase && i < startIndex && strings.isLowerAsciiLetter(chCode)) {
 			return i;
 		}
+		if (chCode === CharCode.Underline) {
+			if (i === 0) {
+				return 0;
+			}
+			const prevChCode = str.charCodeAt(i - 1);
+			if (prevChCode !== CharCode.Underline) {
+				return i - 1;
+			}
+		}
 		ignoreUpperCase = ignoreUpperCase && strings.isUpperAsciiLetter(chCode);
 	}
 	return -1;
@@ -490,7 +508,16 @@ export function _nextWordPartBegin(str: string, startIndex: number = 0): number
 	let ignoreUpperCase = strings.isUpperAsciiLetter(chCode);
 	for (let i = startIndex; i < str.length; ++i) {
 		chCode = str.charCodeAt(i);
-		if (chCode === CharCode.Space || chCode === CharCode.Tab || (!ignoreUpperCase && strings.isUpperAsciiLetter(chCode))) {
+		if (chCode === CharCode.Space || chCode === CharCode.Tab) {
+			if (i + 1 >= str.length) {
+				return i + 1;
+			}
+			const nextChCode = str.charCodeAt(i + 1);
+			if (nextChCode !== CharCode.Space && nextChCode !== CharCode.Tab) {
+				return i + 2;
+			}
+		}
+		if (!ignoreUpperCase && strings.isUpperAsciiLetter(chCode)) {
 			return i + 1;
 		}
 		if (ignoreUpperCase && strings.isLowerAsciiLetter(chCode)) {
@@ -498,7 +525,13 @@ export function _nextWordPartBegin(str: string, startIndex: number = 0): number
 		}
 		ignoreUpperCase = ignoreUpperCase && strings.isUpperAsciiLetter(chCode);
 		if (chCode === CharCode.Underline) {
-			return i + 2;
+			if (i + 1 >= str.length) {
+				return i + 1;
+			}
+			const nextChCode = str.charCodeAt(i + 1);
+			if (nextChCode !== CharCode.Underline) {
+				return i + 2;
+			}
 		}
 	}
 	return str.length + 1;

src/vs/editor/contrib/wordOperations/test/wordTestUtils.ts

@@ -69,6 +69,10 @@ export function testRepeatedActionAndExtractPositions(text: string, initialPosit
 			if (stopCondition(editor)) {
 				break;
 			}
+
+			if (actualStops.length > 1000) {
+				throw new Error(`Endless loop detected!`);
+			}
 		}
 	});
 	return actualStops;

src/vs/editor/contrib/wordPartOperations/test/wordPartOperations.test.ts

@@ -36,7 +36,7 @@ suite('WordPartOperations', () => {
 	test('move word part left basic', () => {
 		const EXPECTED = [
 			'|start| |line|',
-			'|this|Is|A|Camel|Case|Var| | |this|_is|_a|_snake|_case|_var| |THIS|_IS|_CAPS|_SNAKE| |this|_IS|Mixed|Use|',
+			'|this|Is|A|Camel|Case|Var|  |this|_is|_a|_snake|_case|_var| |THIS|_IS|_CAPS|_SNAKE| |this|_IS|Mixed|Use|',
 			'|end| |line'
 		].join('\n');
 		const [text,] = deserializePipePositions(EXPECTED);
@@ -51,10 +51,38 @@ suite('WordPartOperations', () => {
 		assert.deepEqual(actual, EXPECTED);
 	});
 
+	test('issue #53899: move word part left whitespace', () => {
+		const EXPECTED = '|myvar| |=| |\'|demonstration|     |of| |selection| |with| |space\'';
+		const [text,] = deserializePipePositions(EXPECTED);
+		const actualStops = testRepeatedActionAndExtractPositions(
+			text,
+			new Position(1000, 1000),
+			ed => moveWordPartLeft(ed),
+			ed => ed.getPosition(),
+			ed => ed.getPosition().equals(new Position(1, 1))
+		);
+		const actual = serializePipePositions(text, actualStops);
+		assert.deepEqual(actual, EXPECTED);
+	});
+
+	test('issue #53899: move word part left underscores', () => {
+		const EXPECTED = '|myvar| |=| |\'|demonstration|_____of| |selection| |with| |space\'';
+		const [text,] = deserializePipePositions(EXPECTED);
+		const actualStops = testRepeatedActionAndExtractPositions(
+			text,
+			new Position(1000, 1000),
+			ed => moveWordPartLeft(ed),
+			ed => ed.getPosition(),
+			ed => ed.getPosition().equals(new Position(1, 1))
+		);
+		const actual = serializePipePositions(text, actualStops);
+		assert.deepEqual(actual, EXPECTED);
+	});
+
 	test('move word part right basic', () => {
 		const EXPECTED = [
 			'start| |line|',
-			'|this|Is|A|Camel|Case|Var| | |this_|is_|a_|snake_|case_|var| |THIS_|IS_|CAPS_|SNAKE| |this_|IS|Mixed|Use|',
+			'|this|Is|A|Camel|Case|Var|  |this_|is_|a_|snake_|case_|var| |THIS_|IS_|CAPS_|SNAKE| |this_|IS|Mixed|Use|',
 			'|end| |line|'
 		].join('\n');
 		const [text,] = deserializePipePositions(EXPECTED);
@@ -69,6 +97,34 @@ suite('WordPartOperations', () => {
 		assert.deepEqual(actual, EXPECTED);
 	});
 
+	test('issue #53899: move word part right whitespace', () => {
+		const EXPECTED = 'myvar| =| \'demonstration|     |of| |selection| |with| |space|\'|';
+		const [text,] = deserializePipePositions(EXPECTED);
+		const actualStops = testRepeatedActionAndExtractPositions(
+			text,
+			new Position(1, 1),
+			ed => moveWordPartRight(ed),
+			ed => ed.getPosition(),
+			ed => ed.getPosition().equals(new Position(1, 52))
+		);
+		const actual = serializePipePositions(text, actualStops);
+		assert.deepEqual(actual, EXPECTED);
+	});
+
+	test('issue #53899: move word part right underscores', () => {
+		const EXPECTED = 'myvar| =| \'demonstration_____|of| |selection| |with| |space|\'|';
+		const [text,] = deserializePipePositions(EXPECTED);
+		const actualStops = testRepeatedActionAndExtractPositions(
+			text,
+			new Position(1, 1),
+			ed => moveWordPartRight(ed),
+			ed => ed.getPosition(),
+			ed => ed.getPosition().equals(new Position(1, 52))
+		);
+		const actual = serializePipePositions(text, actualStops);
+		assert.deepEqual(actual, EXPECTED);
+	});
+
 	test('delete word part left basic', () => {
 		const EXPECTED = '|   |/*| |Just| |some| |text| |a|+=| |3| |+|5|-|3| |*/|  |this|Is|A|Camel|Case|Var|  |this|_is|_a|_snake|_case|_var| |THIS|_IS|_CAPS|_SNAKE| |this|_IS|Mixed|Use';
 		const [text,] = deserializePipePositions(EXPECTED);