Fix spread operator with debug hover (microsoft#252123)

For microsoft#252122

Author: roblourens

src/vs/workbench/contrib/debug/common/debugUtils.ts

@@ -78,11 +78,14 @@ export function isDebuggerMainContribution(dbg: IDebuggerContribution) {
 	return dbg.type && (dbg.label || dbg.program || dbg.runtime);
 }
 
+/**
+ * Note- uses 1-indexed numbers
+ */
 export function getExactExpressionStartAndEnd(lineContent: string, looseStart: number, looseEnd: number): { start: number; end: number } {
 	let matchingExpression: string | undefined = undefined;
 	let startOffset = 0;
 
-	// Some example supported expressions: myVar.prop, a.b.c.d, myVar?.prop, myVar->prop, MyClass::StaticProp, *myVar
+	// Some example supported expressions: myVar.prop, a.b.c.d, myVar?.prop, myVar->prop, MyClass::StaticProp, *myVar, ...foo
 	// Match any character except a set of characters which often break interesting sub-expressions
 	const expression: RegExp = /([^()\[\]{}<>\s+\-/%~#^;=|,`!]|\->)+/g;
 	let result: RegExpExecArray | null = null;
@@ -99,6 +102,15 @@ export function getExactExpressionStartAndEnd(lineContent: string, looseStart: n
 		}
 	}
 
+	// Handle spread syntax: if the expression starts with '...', extract just the identifier
+	if (matchingExpression) {
+		const spreadMatch = matchingExpression.match(/^\.\.\.(.+)/);
+		if (spreadMatch) {
+			matchingExpression = spreadMatch[1];
+			startOffset += 3; // Skip the '...' prefix
+		}
+	}
+
 	// If there are non-word characters after the cursor, we want to truncate the expression then.
 	// For example in expression 'a.b.c.d', if the focus was under 'b', 'a.b' would be evaluated.
 	if (matchingExpression) {

src/vs/workbench/contrib/debug/test/browser/debugUtils.test.ts

@@ -25,6 +25,7 @@ suite('Debug - Utils', () => {
 
 	test('getExactExpressionStartAndEnd', () => {
 		assert.deepStrictEqual(getExactExpressionStartAndEnd('foo', 1, 2), { start: 1, end: 3 });
+		assert.deepStrictEqual(getExactExpressionStartAndEnd('!foo', 2, 3), { start: 2, end: 4 });
 		assert.deepStrictEqual(getExactExpressionStartAndEnd('foo', 1, 3), { start: 1, end: 3 });
 		assert.deepStrictEqual(getExactExpressionStartAndEnd('foo', 1, 4), { start: 1, end: 3 });
 		assert.deepStrictEqual(getExactExpressionStartAndEnd('this.name = "John"', 1, 10), { start: 1, end: 9 });
@@ -44,6 +45,10 @@ suite('Debug - Utils', () => {
 
 		assert.deepStrictEqual(getExactExpressionStartAndEnd('var aøñéå文 = a.b.c-d.name', 5, 5), { start: 5, end: 10 });
 		assert.deepStrictEqual(getExactExpressionStartAndEnd('aøñéå文.aøñéå文.aøñéå文', 9, 9), { start: 1, end: 13 });
+
+		// Spread syntax should extract just the identifier
+		assert.deepStrictEqual(getExactExpressionStartAndEnd('[...bar]', 5, 7), { start: 5, end: 7 });
+		assert.deepStrictEqual(getExactExpressionStartAndEnd('...variable', 5, 5), { start: 4, end: 11 });
 	});
 
 	test('config presentation', () => {