chore: enable strict index checks

.changeset/dirty-rats-change.md

@@ -0,0 +1,6 @@
+---
+"@clack/prompts": patch
+"@clack/core": patch
+---
+
+Handle empty arrays in various prompts and utilities.

packages/core/src/prompts/autocomplete.ts

@@ -86,9 +86,10 @@ export default class AutocompletePrompt<T extends OptionLike> extends Prompt<
 		if (this._cursor >= this.userInput.length) {
 			return `${this.userInput}█`;
 		}
-		const s1 = this.userInput.slice(0, this._cursor);
-		const [s2, ...s3] = this.userInput.slice(this._cursor);
-		return `${s1}${styleText('inverse', s2)}${s3.join('')}`;
+		const preCursor = this.userInput.slice(0, this.cursor);
+		const cursorChar = this.userInput.slice(this.cursor, this.cursor + 1);
+		const rest = this.userInput.slice(this.cursor + 1);
+		return `${preCursor}${styleText('inverse', cursorChar)}${rest}`;
 	}
 
 	get options(): T[] {
@@ -117,7 +118,7 @@ export default class AutocompletePrompt<T extends OptionLike> extends Prompt<
 			}
 		} else {
 			if (!this.multiple && this.options.length > 0) {
-				initialValues = [this.options[0].value];
+				initialValues = [this.options[0]?.value];
 			}
 		}
 

packages/core/src/prompts/date.ts

@@ -22,7 +22,8 @@ const SEGMENTS: Record<string, SegmentConfig> = {
 } as const;
 
 function segmentsFor(fmt: DateFormat): SegmentConfig[] {
-	return [...fmt].map((c) => SEGMENTS[c as keyof typeof SEGMENTS]);
+	// biome-ignore lint/style/noNonNullAssertion: DateFormat only contains Y/M/D keys present in SEGMENTS
+	return [...fmt].map((c) => SEGMENTS[c as keyof typeof SEGMENTS]!);
 }
 
 function detectLocaleFormat(locale?: string): { segments: SegmentConfig[]; separator: string } {

packages/core/src/prompts/group-multiselect.ts

@@ -28,6 +28,9 @@ export default class GroupMultiSelectPrompt<T extends { value: any }> extends Pr
 
 	private toggleValue() {
 		const item = this.options[this.cursor];
+		if (item === undefined) {
+			return;
+		}
 		if (this.value === undefined) {
 			this.value = [];
 		}

packages/core/src/prompts/multi-line.ts

@@ -25,11 +25,11 @@ export default class MultiLinePrompt extends Prompt<string> {
 		if (this.cursor >= userInput.length) {
 			return `${userInput}█`;
 		}
-		const s1 = userInput.slice(0, this.cursor);
-		const s2 = userInput[this.cursor];
-		const s3 = userInput.slice(this.cursor + 1);
-		if (s2 === '\n') return `${s1}█\n${s3}`;
-		return `${s1}${styleText('inverse', s2)}${s3}`;
+		const preCursor = userInput.slice(0, this.cursor);
+		const cursorChar = userInput.slice(this.cursor, this.cursor + 1);
+		const rest = userInput.slice(this.cursor + 1);
+		if (cursorChar === '\n') return `${preCursor}█\n${rest}`;
+		return `${preCursor}${styleText('inverse', cursorChar)}${rest}`;
 	}
 	get cursor() {
 		return this._cursor;

packages/core/src/prompts/multi-select.ts

@@ -18,7 +18,7 @@ export default class MultiSelectPrompt<T extends OptionLike> extends Prompt<T['v
 	cursor = 0;
 
 	private get _value(): T['value'] {
-		return this.options[this.cursor].value;
+		return this.options[this.cursor]?.value;
 	}
 
 	private get _enabledOptions(): T[] {
@@ -59,7 +59,7 @@ export default class MultiSelectPrompt<T extends OptionLike> extends Prompt<T['v
 			this.options.findIndex(({ value }) => value === opts.cursorAt),
 			0
 		);
-		this.cursor = this.options[cursor].disabled ? findCursor<T>(cursor, 1, this.options) : cursor;
+		this.cursor = this.options[cursor]?.disabled ? findCursor<T>(cursor, 1, this.options) : cursor;
 		this.on('key', (_char, key) => {
 			if (key.name === 'a') {
 				this.toggleAll();

packages/core/src/prompts/password.ts

@@ -21,9 +21,10 @@ export default class PasswordPrompt extends Prompt<string> {
 			return `${this.masked}${styleText(['inverse', 'hidden'], '_')}`;
 		}
 		const masked = this.masked;
-		const s1 = masked.slice(0, this.cursor);
-		const s2 = masked.slice(this.cursor);
-		return `${s1}${styleText('inverse', s2[0])}${s2.slice(1)}`;
+		const preCursor = masked.slice(0, this.cursor);
+		const cursorChar = masked.slice(this.cursor, this.cursor + 1);
+		const rest = masked.slice(this.cursor + 1);
+		return `${preCursor}${styleText('inverse', cursorChar)}${rest}`;
 	}
 	clear() {
 		this._clearUserInput();

packages/core/src/prompts/select.ts

@@ -17,7 +17,8 @@ export default class SelectPrompt<T extends { value: any; disabled?: boolean }>
 	}
 
 	private changeValue() {
-		this.value = this._selectedValue.value;
+		const selectedValue = this._selectedValue;
+		this.value = selectedValue === undefined ? undefined : selectedValue.value;
 	}
 
 	constructor(opts: SelectOptions<T>) {
@@ -27,7 +28,7 @@ export default class SelectPrompt<T extends { value: any; disabled?: boolean }>
 
 		const initialCursor = this.options.findIndex(({ value }) => value === opts.initialValue);
 		const cursor = initialCursor === -1 ? 0 : initialCursor;
-		this.cursor = this.options[cursor].disabled ? findCursor<T>(cursor, 1, this.options) : cursor;
+		this.cursor = this.options[cursor]?.disabled ? findCursor<T>(cursor, 1, this.options) : cursor;
 		this.changeValue();
 
 		this.on('cursor', (key) => {

packages/core/src/prompts/text.ts

@@ -15,9 +15,10 @@ export default class TextPrompt extends Prompt<string> {
 		if (this.cursor >= userInput.length) {
 			return `${this.userInput}█`;
 		}
-		const s1 = userInput.slice(0, this.cursor);
-		const [s2, ...s3] = userInput.slice(this.cursor);
-		return `${s1}${styleText('inverse', s2)}${s3.join('')}`;
+		const preCursor = userInput.slice(0, this.cursor);
+		const cursorChar = userInput.slice(this.cursor, this.cursor + 1);
+		const rest = userInput.slice(this.cursor + 1);
+		return `${preCursor}${styleText('inverse', cursorChar)}${rest}`;
 	}
 	get cursor() {
 		return this._cursor;

packages/core/src/utils/cursor.ts

@@ -11,7 +11,7 @@ export function findCursor<T extends { disabled?: boolean }>(
 	const maxCursor = Math.max(options.length - 1, 0);
 	const clampedCursor = newCursor < 0 ? maxCursor : newCursor > maxCursor ? 0 : newCursor;
 	const newOption = options[clampedCursor];
-	if (newOption.disabled) {
+	if (newOption?.disabled) {
 		return findCursor(clampedCursor, delta < 0 ? -1 : 1, options);
 	}
 	return clampedCursor;
@@ -37,20 +37,22 @@ export function findTextCursor(
 
 	cursorY = Math.max(0, Math.min(lines.length - 1, cursorY + deltaY));
 
-	cursorX = Math.min(cursorX, lines[cursorY].length) + deltaX;
+	// biome-ignore-start lint/style/noNonNullAssertion: cursorY/i are always kept within lines bounds
+	cursorX = Math.min(cursorX, lines[cursorY]!.length) + deltaX;
 	while (cursorX < 0 && cursorY > 0) {
 		cursorY--;
-		cursorX += lines[cursorY].length + 1;
+		cursorX += lines[cursorY]!.length + 1;
 	}
-	while (cursorX > lines[cursorY].length && cursorY < lines.length - 1) {
-		cursorX -= lines[cursorY].length + 1;
+	while (cursorX > lines[cursorY]!.length && cursorY < lines.length - 1) {
+		cursorX -= lines[cursorY]!.length + 1;
 		cursorY++;
 	}
-	cursorX = Math.max(0, Math.min(lines[cursorY].length, cursorX));
+	cursorX = Math.max(0, Math.min(lines[cursorY]!.length, cursorX));
 
 	let newCursor = 0;
 	for (let i = 0; i < cursorY; i++) {
-		newCursor += lines[i].length + 1;
+		newCursor += lines[i]!.length + 1;
 	}
+	// biome-ignore-end lint/style/noNonNullAssertion: end of clamped cursor block
 	return newCursor + cursorX;
 }

packages/core/src/utils/settings.ts

@@ -123,7 +123,7 @@ export function updateSettings(updates: ClackSettings) {
 			if (!Object.hasOwn(aliases, alias)) continue;
 
 			const action = aliases[alias];
-			if (!settings.actions.has(action)) continue;
+			if (action === undefined || !settings.actions.has(action)) continue;
 
 			if (!settings.aliases.has(alias)) {
 				settings.aliases.set(alias, action);

packages/core/test/prompts/date.test.ts

@@ -6,7 +6,7 @@ import { MockReadable } from '../mock-readable.js';
 import { MockWritable } from '../mock-writable.js';
 
 const d = (iso: string) => {
-	const [y, m, day] = iso.slice(0, 10).split('-').map(Number);
+	const [y, m, day] = iso.slice(0, 10).split('-').map(Number) as [number, number, number];
 	return new Date(Date.UTC(y, m - 1, day));
 };
 
@@ -407,9 +407,9 @@ describe('DatePrompt', () => {
 			});
 			instance.prompt();
 			// en-US is MDY
-			expect(instance.segments[0].type).to.equal('month');
-			expect(instance.segments[1].type).to.equal('day');
-			expect(instance.segments[2].type).to.equal('year');
+			expect(instance.segments[0]?.type).to.equal('month');
+			expect(instance.segments[1]?.type).to.equal('day');
+			expect(instance.segments[2]?.type).to.equal('year');
 		});
 
 		test('explicit format overrides locale', () => {
@@ -422,7 +422,7 @@ describe('DatePrompt', () => {
 				initialValue: d('2025-03-15'),
 			});
 			instance.prompt();
-			expect(instance.segments[0].type).to.equal('year');
+			expect(instance.segments[0]?.type).to.equal('year');
 		});
 	});
 });

packages/core/test/prompts/group-multiselect.test.ts

@@ -0,0 +1,43 @@
+import { cursor } from 'sisteransi';
+import { afterEach, beforeEach, describe, expect, test, vi } from 'vitest';
+import { default as GroupMultiSelectPrompt } from '../../src/prompts/group-multiselect.js';
+import { MockReadable } from '../mock-readable.js';
+import { MockWritable } from '../mock-writable.js';
+
+describe('GroupMultiSelectPrompt', () => {
+	let input: MockReadable;
+	let output: MockWritable;
+
+	beforeEach(() => {
+		input = new MockReadable();
+		output = new MockWritable();
+	});
+
+	afterEach(() => {
+		vi.restoreAllMocks();
+	});
+
+	test('renders render() result', () => {
+		const instance = new GroupMultiSelectPrompt({
+			input,
+			output,
+			render: () => 'foo',
+			options: {
+				group: [{ value: 'foo' }, { value: 'bar' }],
+			},
+		});
+		instance.prompt();
+		expect(output.buffer).to.deep.equal([cursor.hide, 'foo']);
+	});
+
+	test('does not throw if empty options are provided', () => {
+		const instance = new GroupMultiSelectPrompt({
+			input,
+			output,
+			render: () => 'foo',
+			options: {},
+		});
+		instance.prompt();
+		expect(() => input.emit('keypress', ' ', { name: 'space' })).not.toThrow();
+	});
+});

packages/core/test/prompts/multi-select.test.ts

@@ -28,6 +28,18 @@ describe('MultiSelectPrompt', () => {
 		expect(output.buffer).to.deep.equal([cursor.hide, 'foo']);
 	});
 
+	test('does not throw if empty options are provided', () => {
+		expect(
+			() =>
+				new MultiSelectPrompt({
+					input,
+					output,
+					render: () => 'foo',
+					options: [],
+				})
+		).not.toThrow();
+	});
+
 	describe('cursor', () => {
 		test('cursor is index of selected item', () => {
 			const instance = new MultiSelectPrompt({

packages/core/test/prompts/select.test.ts

@@ -28,6 +28,16 @@ describe('SelectPrompt', () => {
 		expect(output.buffer).to.deep.equal([cursor.hide, 'foo']);
 	});
 
+	test('does not throw if empty options are provided', () => {
+		const instance = new SelectPrompt({
+			input,
+			output,
+			render: () => 'foo',
+			options: [],
+		});
+		expect(() => instance.prompt()).not.toThrow();
+	});
+
 	describe('cursor', () => {
 		test('cursor is index of selected item', () => {
 			const instance = new SelectPrompt({

packages/prompts/src/group-multi-select.ts

@@ -237,7 +237,7 @@ export const groupMultiselect = <Value>(opts: GroupMultiSelectOptions<Value>) =>
 				const groupActive =
 					!active &&
 					typeof option.group === 'string' &&
-					this.options[this.cursor].value === option.group;
+					this.options[this.cursor]?.value === option.group;
 				if (groupActive) {
 					return opt(option, selected ? 'group-active-selected' : 'group-active', options);
 				}

packages/prompts/src/limit-options.ts

@@ -56,13 +56,19 @@ const trimLines = (
 	let removals = 0;
 	if (fromEnd) {
 		for (let i = endIndex - 1; i >= startIndex; i--) {
-			lineCount -= groups[i].length;
+			const group = groups[i];
+			if (group) {
+				lineCount -= group.length;
+			}
 			removals++;
 			if (lineCount <= maxLines) break;
 		}
 	} else {
 		for (let i = startIndex; i < endIndex; i++) {
-			lineCount -= groups[i].length;
+			const group = groups[i];
+			if (group) {
+				lineCount -= group.length;
+			}
 			removals++;
 			if (lineCount <= maxLines) break;
 		}
@@ -142,7 +148,9 @@ export const limitOptions = <TOption>({
 		slidingWindowLocationEnd - (shouldRenderBottomEllipsis ? 1 : 0);
 
 	for (let i = slidingWindowLocationWithEllipsis; i < slidingWindowLocationEndWithEllipsis; i++) {
-		const wrappedLines = wrapAnsi(style(options[i], i === cursor), maxWidth, {
+		const option = options[i];
+		const styledOption = option ? style(option, i === cursor) : '';
+		const wrappedLines = wrapAnsi(styledOption, maxWidth, {
 			hard: true,
 			trim: false,
 		}).split('\n');

packages/prompts/src/log.ts

@@ -39,7 +39,7 @@ export const log = {
 
 		const messageParts = Array.isArray(message) ? message : message.split('\n');
 		if (messageParts.length > 0) {
-			const [firstLine, ...lines] = messageParts;
+			const [firstLine, ...lines] = messageParts as [string, ...string[]];
 			if (firstLine.length > 0) {
 				parts.push(`${prefix}${firstLine}`);
 			} else {

packages/prompts/src/multi-line.ts

@@ -47,9 +47,11 @@ export const multiline = (opts: MultiLineOptions) => {
 			const hasGuide = opts?.withGuide ?? settings.withGuide;
 			const titlePrefix = `${hasGuide ? `${styleText('gray', S_BAR)}\n` : ''}${symbol(this.state)}  `;
 			const title = `${titlePrefix}${opts.message}\n`;
-			const placeholder = opts.placeholder
-				? styleText('inverse', opts.placeholder[0]) + styleText('dim', opts.placeholder.slice(1))
-				: styleText(['inverse', 'hidden'], '_');
+			const placeholder =
+				opts.placeholder && opts.placeholder.length > 0
+					? // biome-ignore lint/style/noNonNullAssertion: guarded by placeholder.length > 0
+						styleText('inverse', opts.placeholder[0]!) + styleText('dim', opts.placeholder.slice(1))
+					: styleText(['inverse', 'hidden'], '_');
 			const userInput = !this.userInput ? placeholder : this.userInputWithCursor;
 			const value = this.value ?? '';
 			const submitButton = opts.showSubmit

packages/prompts/src/select-key.ts

@@ -12,9 +12,12 @@ export interface SelectKeyOptions<Value extends string> extends CommonOptions {
 
 export const selectKey = <Value extends string>(opts: SelectKeyOptions<Value>) => {
 	const opt = (
-		option: Option<Value>,
+		option: Option<Value> | undefined,
 		state: 'inactive' | 'active' | 'selected' | 'cancelled' = 'inactive'
 	) => {
+		if (option === undefined) {
+			return '';
+		}
 		const label = option.label ?? String(option.value);
 		if (state === 'selected') {
 			return `${styleText('dim', label)}`;

packages/prompts/src/select.ts

@@ -95,9 +95,12 @@ const computeLabel = (label: string, format: (text: string) => string) => {
 
 export const select = <Value>(opts: SelectOptions<Value>) => {
 	const opt = (
-		option: Option<Value>,
+		option: Option<Value> | undefined,
 		state: 'inactive' | 'active' | 'selected' | 'cancelled' | 'disabled'
 	) => {
+		if (option === undefined) {
+			return '';
+		}
 		const label = option.label ?? String(option.value);
 		switch (state) {
 			case 'disabled':

packages/prompts/src/spinner.ts

@@ -146,7 +146,8 @@ export const spinner = ({
 			}
 			clearPrevMessage();
 			_prevMessage = _message;
-			const frame = styleFn(frames[frameIndex]);
+			// biome-ignore lint/style/noNonNullAssertion: frameIndex is always kept within frames bounds
+			const frame = styleFn(frames[frameIndex]!);
 			let outputMessage: string;
 
 			if (isCI) {