Add array.exactShape predicate (#187)

Co-authored-by: Sindre Sorhus <[email protected]>

source/predicates/array.ts

@@ -2,6 +2,8 @@ import isEqual = require('lodash.isequal');
 import {BasePredicate} from './base-predicate';
 import {Predicate, PredicateOptions} from './predicate';
 import ow from '..';
+import {Shape} from './object';
+import {exact} from '../utils/match-shape';
 
 export class ArrayPredicate<T = unknown> extends Predicate<T[]> {
 	/**
@@ -159,4 +161,23 @@ export class ArrayPredicate<T = unknown> extends Predicate<T[]> {
 			}
 		}) as ArrayPredicate<any>;
 	}
+
+	/**
+	Test if the elements in the array exactly matches the elements placed at the same indices in the predicates array.
+
+	@param predicates - Predicates to test the array against. Describes what the tested array should look like.
+
+	@example
+	```
+	ow(['1', 2], ow.array.exactShape([ow.string, ow.number]));
+	```
+	*/
+	exactShape(predicates: Predicate[]) {
+		const shape = predicates as unknown as Shape;
+
+		return this.addValidator({
+			message: (_, label, message) => `${message.replace('Expected', 'Expected element')} in ${label}`,
+			validator: object => exact(object, shape, undefined, true)
+		});
+	}
 }

source/utils/match-shape.ts

@@ -76,7 +76,7 @@ Test if the `object` matches the `shape` exactly.
 @param shape - Shape to test the object against.
 @param parent - Name of the parent property.
 */
-export function exact(object: Record<string, any>, shape: Shape, parent?: string): boolean | string {
+export function exact(object: Record<string, any>, shape: Shape, parent?: string, isArray?: boolean): boolean | string {
 	const stack = generateStackTrace();
 	try {
 		const objectKeys = new Set<string>(Object.keys(object));
@@ -104,7 +104,7 @@ export function exact(object: Record<string, any>, shape: Shape, parent?: string
 		if (objectKeys.size > 0) {
 			const firstKey = [...objectKeys.keys()][0]!;
 			const label = parent ? `${parent}.${firstKey}` : firstKey;
-			return `Did not expect property \`${label}\` to exist, got \`${object[firstKey]}\``;
+			return `Did not expect ${isArray ? 'element' : 'property'} \`${label}\` to exist, got \`${object[firstKey]}\``;
 		}
 
 		return true;

test/array.ts

@@ -168,3 +168,21 @@ test('array.ofType', t => {
 		ow(['foo', 'b'], 'foo', ow.array.ofType(ow.string.minLength(3)));
 	}, '(array `foo`) Expected string to have a minimum length of `3`, got `b`');
 });
+
+test('array.exactShape', t => {
+	t.notThrows(() => {
+		ow(['🦄', 2, 3, true, {isFirstCommit: true}], ow.array.exactShape([ow.string, ow.number, ow.number, ow.boolean, ow.object.exactShape({isFirstCommit: ow.boolean})]));
+	});
+
+	t.throws(() => {
+		ow(['🦄', 2, 'nope', true, {isFirstCommit: true}], ow.array.exactShape([ow.string, ow.number, ow.number, ow.boolean, ow.object.exactShape({isFirstCommit: ow.string})]));
+	}, 'Expected element `2` to be of type `number` but received type `string` in array');
+
+	t.throws(() => {
+		ow(['🦄', 'nope', {isFirstCommit: true}], ow.array.exactShape([ow.string, ow.string, ow.object.exactShape({isFirstCommit: ow.boolean}), ow.number, ow.boolean]));
+	}, 'Expected element `3` to be of type `number` but received type `undefined` in array');
+
+	t.throws(() => {
+		ow(['🦄', {isFirstCommit: true}, 'nope', 5, {accepted: false}], ow.array.exactShape([ow.string, ow.object.exactShape({isFirstCommit: ow.boolean}), ow.string]));
+	}, 'Did not expect element `3` to exist, got `5` in array');
+});