feat: auto-trigger parameter hints when cursor enters argument list

src/vs/editor/common/config/editorOptions.ts

@@ -3659,6 +3659,11 @@ export interface IEditorParameterHintOptions {
 	 * Defaults to false.
 	 */
 	cycle?: boolean;
+	/**
+	 * Automatically show parameter hints when the cursor enters an unmatched open parenthesis.
+	 * Defaults to false.
+	 */
+	autoTriggerOnCursorInArgs?: boolean;
 }
 
 /**
@@ -3671,7 +3676,8 @@ class EditorParameterHints extends BaseEditorOption<EditorOption.parameterHints,
 	constructor() {
 		const defaults: InternalParameterHintOptions = {
 			enabled: true,
-			cycle: true
+			cycle: true,
+			autoTriggerOnCursorInArgs: false
 		};
 		super(
 			EditorOption.parameterHints, 'parameterHints', defaults,
@@ -3686,6 +3692,11 @@ class EditorParameterHints extends BaseEditorOption<EditorOption.parameterHints,
 					default: defaults.cycle,
 					description: nls.localize('parameterHints.cycle', "Controls whether the parameter hints menu cycles or closes when reaching the end of the list.")
 				},
+				'editor.parameterHints.autoTriggerOnCursorInArgs': {
+					type: 'boolean',
+					default: defaults.autoTriggerOnCursorInArgs,
+					description: nls.localize('parameterHints.autoTriggerOnCursorInArgs', "Controls whether parameter hints are automatically shown when the cursor moves into an existing, unmatched opening parenthesis.")
+				},
 			}
 		);
 	}
@@ -3697,7 +3708,8 @@ class EditorParameterHints extends BaseEditorOption<EditorOption.parameterHints,
 		const input = _input as Unknown<IEditorParameterHintOptions>;
 		return {
 			enabled: boolean(input.enabled, this.defaultValue.enabled),
-			cycle: boolean(input.cycle, this.defaultValue.cycle)
+			cycle: boolean(input.cycle, this.defaultValue.cycle),
+			autoTriggerOnCursorInArgs: boolean(input.autoTriggerOnCursorInArgs, this.defaultValue.autoTriggerOnCursorInArgs)
 		};
 	}
 }

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

@@ -58,6 +58,7 @@ export class ParameterHintsModel extends Disposable {
 	private readonly providers: LanguageFeatureRegistry<languages.SignatureHelpProvider>;
 
 	private triggerOnType = false;
+	private autoTriggerOnCursorInArgs = false;
 	private _state: ParameterHintState.State = ParameterHintState.Default;
 	private _pendingTriggers: TriggerContext[] = [];
 
@@ -294,11 +295,51 @@ export class ParameterHintsModel extends Disposable {
 	}
 
 	private onCursorChange(e: ICursorSelectionChangedEvent): void {
-		if (e.source === 'mouse') {
-			this.cancel();
-		} else if (this.isTriggered) {
+		if (this.isTriggered) {
 			this.trigger({ triggerKind: languages.SignatureHelpTriggerKind.ContentChange });
+		} else if (e.source === 'mouse') {
+			if (this.autoTriggerOnCursorInArgs && this.triggerOnType && this.isCursorInsideArgumentList()) {
+				this.trigger({ triggerKind: languages.SignatureHelpTriggerKind.Invoke });
+			} else {
+				this.cancel();
+			}
+		} else if (this.autoTriggerOnCursorInArgs && this.triggerOnType && this.isCursorInsideArgumentList()) {
+			this.trigger({ triggerKind: languages.SignatureHelpTriggerKind.Invoke });
+		}
+	}
+
+	private isCursorInsideArgumentList(): boolean {
+		const model = this.editor.getModel();
+		const position = this.editor.getPosition();
+		if (!model || !position) {
+			return false;
+		}
+		const text = model.getLineContent(position.lineNumber).substring(0, position.column - 1);
+		let depth = 0;
+		let inSingle = false;
+		let inDouble = false;
+		let inBacktick = false;
+		for (let i = 0; i < text.length; i++) {
+			const ch = text.charAt(i);
+			if (ch === '\\' && i + 1 < text.length) {
+				i++;
+				continue;
+			}
+			if (!inDouble && !inBacktick && ch === '\'') {
+				inSingle = !inSingle;
+			} else if (!inSingle && !inBacktick && ch === '"') {
+				inDouble = !inDouble;
+			} else if (!inSingle && !inDouble && ch === '`') {
+				inBacktick = !inBacktick;
+			} else if (!inSingle && !inDouble && !inBacktick) {
+				if (ch === '(') {
+					depth++;
+				} else if (ch === ')' && depth > 0) {
+					depth--;
+				}
+			}
 		}
+		return depth > 0;
 	}
 
 	private onModelContentChange(): void {
@@ -308,7 +349,9 @@ export class ParameterHintsModel extends Disposable {
 	}
 
 	private onEditorConfigurationChange(): void {
-		this.triggerOnType = this.editor.getOption(EditorOption.parameterHints).enabled;
+		const options = this.editor.getOption(EditorOption.parameterHints);
+		this.triggerOnType = options.enabled;
+		this.autoTriggerOnCursorInArgs = options.autoTriggerOnCursorInArgs;
 
 		if (!this.triggerOnType) {
 			this.cancel();