[VSCodeSweeper MVP — test only] lsp signature_helper Activity parameter highlight position error

src/vs/editor/contrib/parameterHints/browser/parameterHintsWidget.ts

@@ -311,21 +311,7 @@ export class ParameterHintsWidget extends Disposable implements IContentWidget {
 	}
 
 	private getParameterLabelOffsets(signature: languages.SignatureInformation, paramIdx: number): [number, number] {
-		const param = signature.parameters[paramIdx];
-		if (!param) {
-			return [0, 0];
-		} else if (Array.isArray(param.label)) {
-			return param.label;
-		} else if (!param.label.length) {
-			return [0, 0];
-		} else {
-			const regex = new RegExp(`(\\W|^)${escapeRegExpCharacters(param.label)}(?=\\W|$)`, 'g');
-			regex.test(signature.label);
-			const idx = regex.lastIndex - param.label.length;
-			return idx >= 0
-				? [idx, regex.lastIndex]
-				: [0, 0];
-		}
+		return getParameterLabelOffsets(signature, paramIdx);
 	}
 
 	next(): void {
@@ -364,4 +350,46 @@ export class ParameterHintsWidget extends Disposable implements IContentWidget {
 	}
 }
 
+/**
+ * Computes the [start, end) offsets of the parameter label within the signature label string.
+ * Accounts for earlier parameters so that duplicate names are resolved to the correct occurrence.
+ */
+export function getParameterLabelOffsets(signature: languages.SignatureInformation, paramIdx: number): [number, number] {
+	const param = signature.parameters[paramIdx];
+	if (!param) {
+		return [0, 0];
+	} else if (Array.isArray(param.label)) {
+		return param.label;
+	} else if (!param.label.length) {
+		return [0, 0];
+	} else {
+		// Determine a search start offset by finding the end of the previous parameter's position.
+		// This prevents matching a parameter name that appears in an earlier part of the label.
+		let searchStart = 0;
+		for (let i = 0; i < paramIdx; i++) {
+			const prev = signature.parameters[i];
+			if (!prev) {
+				break;
+			}
+			if (Array.isArray(prev.label)) {
+				searchStart = Math.max(searchStart, prev.label[1]);
+			} else if (prev.label.length) {
+				const prevRegex = new RegExp(`(\\W|^)${escapeRegExpCharacters(prev.label)}(?=\\W|$)`, 'g');
+				prevRegex.lastIndex = searchStart;
+				if (prevRegex.test(signature.label)) {
+					searchStart = prevRegex.lastIndex;
+				}
+			}
+		}
+
+		const regex = new RegExp(`(\\W|^)${escapeRegExpCharacters(param.label)}(?=\\W|$)`, 'g');
+		regex.lastIndex = searchStart;
+		regex.test(signature.label);
+		const idx = regex.lastIndex - param.label.length;
+		return idx >= searchStart
+			? [idx, regex.lastIndex]
+			: [0, 0];
+	}
+}
+
 registerColor('editorHoverWidget.highlightForeground', listHighlightForeground, nls.localize('editorHoverWidgetHighlightForeground', 'Foreground color of the active item in the parameter hint.'));

src/vs/editor/contrib/parameterHints/test/browser/parameterHintsWidget.test.ts

@@ -0,0 +1,120 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import assert from 'assert';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../base/test/common/utils.js';
+import * as languages from '../../../../common/languages.js';
+import { getParameterLabelOffsets } from '../../browser/parameterHintsWidget.js';
+
+suite('ParameterHintsWidget - getParameterLabelOffsets', () => {
+
+	ensureNoDisposablesAreLeakedInTestSuite();
+
+	test('should return correct offsets for simple parameter', () => {
+		const signature: languages.SignatureInformation = {
+			label: 'foo(x, y)',
+			parameters: [
+				{ label: 'x', documentation: '' },
+				{ label: 'y', documentation: '' },
+			]
+		};
+
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 0), [4, 5]);
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 1), [7, 8]);
+	});
+
+	test('should return tuple label as-is', () => {
+		const signature: languages.SignatureInformation = {
+			label: 'foo(x, y)',
+			parameters: [
+				{ label: [4, 5] as [number, number], documentation: '' },
+				{ label: [7, 8] as [number, number], documentation: '' },
+			]
+		};
+
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 0), [4, 5]);
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 1), [7, 8]);
+	});
+
+	test('should highlight correct occurrence when parameter name appears earlier in signature', () => {
+		// "len" appears in "strlen" and also as a parameter name
+		const signature: languages.SignatureInformation = {
+			label: 'strlen(len, len)',
+			parameters: [
+				{ label: 'len', documentation: '' },
+				{ label: 'len', documentation: '' },
+			]
+		};
+
+		// First "len" parameter should match at position 7-10
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 0), [7, 10]);
+		// Second "len" parameter should match at position 12-15
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 1), [12, 15]);
+	});
+
+	test('should highlight correct parameter when name is substring of function name', () => {
+		// Issue #246019: "len" appears in function name "strlen"
+		const signature: languages.SignatureInformation = {
+			label: 'strlen(str, len)',
+			parameters: [
+				{ label: 'str', documentation: '' },
+				{ label: 'len', documentation: '' },
+			]
+		};
+
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 0), [7, 10]);
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 1), [12, 15]);
+	});
+
+	test('should handle duplicate parameter names correctly', () => {
+		const signature: languages.SignatureInformation = {
+			label: 'func(a, a, a)',
+			parameters: [
+				{ label: 'a', documentation: '' },
+				{ label: 'a', documentation: '' },
+				{ label: 'a', documentation: '' },
+			]
+		};
+
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 0), [5, 6]);
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 1), [8, 9]);
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 2), [11, 12]);
+	});
+
+	test('should return [0, 0] for missing parameter', () => {
+		const signature: languages.SignatureInformation = {
+			label: 'foo(x)',
+			parameters: [
+				{ label: 'x', documentation: '' },
+			]
+		};
+
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 5), [0, 0]);
+	});
+
+	test('should return [0, 0] for empty parameter label', () => {
+		const signature: languages.SignatureInformation = {
+			label: 'foo(x)',
+			parameters: [
+				{ label: '', documentation: '' },
+			]
+		};
+
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 0), [0, 0]);
+	});
+
+	test('should handle mixed tuple and string labels', () => {
+		const signature: languages.SignatureInformation = {
+			label: 'foo(len, len)',
+			parameters: [
+				{ label: [4, 7] as [number, number], documentation: '' },
+				{ label: 'len', documentation: '' },
+			]
+		};
+
+		// Second parameter should find "len" after position 7
+		assert.deepStrictEqual(getParameterLabelOffsets(signature, 1), [9, 12]);
+	});
+});