Add readonly array support for some packages (#496)

* improve type definition of array-group-by

* improve type definition of array-flatten

* improve type definition of array-index

packages/array-flatten/index.d.ts

@@ -1,4 +1,4 @@
-type RecursiveList<T> = (T | T[] | RecursiveList<T>)[];
+type RecursiveList<T> = readonly (T | readonly T[] | RecursiveList<T>)[];
 
 /**
  * Flattens an array
@@ -11,5 +11,5 @@ type RecursiveList<T> = (T | T[] | RecursiveList<T>)[];
  * flatten([[1, [2, 3]], [[4, 5], 6, 7, [8, 9]]], 1);
  * // => [1, [2, 3], [[4, 5], 6, 7, [8, 9]]]
  */
-declare function flatten<T>(arr: RecursiveList<T>, depth? : number): T[];
+declare function flatten<T>(arr: RecursiveList<T>, depth?: number): T[];
 export default flatten;

packages/array-flatten/index.tests.ts

@@ -1,10 +1,11 @@
 import flatten from './index'
 
 // OK
-flatten([1, 2, 3]);
-flatten([1, [2, 3], 4]);
-flatten([1, [2, [3]], 4]);
-flatten([1, [2, [3]], [[[[[4]]]]]]);
+const numbers: readonly number[] = [1, 2, 3]
+flatten(numbers);
+flatten([1, numbers, 4]);
+flatten([1, [2, numbers], 4]);
+flatten([1, [2, [3]], [[[[numbers]]]]]);
 flatten([1, [2, [3]], [[[[[4]]]]]], 2);
 flatten([1, [2, [3]], [[[[[4]]]]]], undefined);
 
@@ -16,7 +17,7 @@ flatten(true);
 // @ts-expect-error
 flatten(null);
 // @ts-expect-error
-flatten({a: 5});
+flatten({ a: 5 });
 // @ts-expect-error
 flatten([1], true);
 // @ts-expect-error

packages/array-group-by/index.d.ts

@@ -4,6 +4,6 @@
  * @param resolver function used to resolve group key
  */
 export default function groupBy<T, G extends keyof any = keyof any>(
-  arr: T[],
+  arr: readonly T[],
   resolver: (arg: T) => G
 ): Record<G, T[]>;

packages/array-group-by/index.tests.ts

@@ -1,7 +1,8 @@
 import groupBy from './index';
 
 // OK
-const test1: { [key: string]: number[] } = groupBy([6.1, 4.2, 6.3], Math.floor);
+const numbers: readonly number[] = [6.1, 4.2, 6.3]
+const test1: { [key: string]: number[] } = groupBy(numbers, Math.floor);
 const test2: { [key: string]: string[] } = groupBy(
   ['a', 'b', 'c', 'aa', 'bb', 'cc'],
   str => str.charAt(0)

packages/array-index/index.d.ts

@@ -14,5 +14,5 @@
  * index([{id: 0, val: 0}, {id: 0, val: 1}], 'id');
  * // => {first: {id: 0, val: 1}}
  */
-declare function index<T>(arr: Array<T|null|undefined>, key: string): Record<string, T>;
+declare function index<T>(arr: readonly (T | null | undefined)[], key: string): Record<string, T>;
 export default index;

packages/array-index/index.tests.ts

@@ -1,13 +1,14 @@
 import index from './index'
 
 // OK
-index([ { a: 5 }, { a: 6 } ], 'a');
-index([ { a: 5 }, { a: 6 }, null, undefined ], 'a');
-index([ { a: 5 }, { a: 6 } ], 'b');
+const objects: readonly Record<string, number>[] = [{ a: 5 }, { a: 6 }]
+index(objects, 'a');
+index([{ a: 5 }, { a: 6 }, null, undefined], 'a');
+index([{ a: 5 }, { a: 6 }], 'b');
 index([1, 2, 3], 'a');
 
 // Not OK
 // @ts-expect-error
-index([ { a: 5 }, { a: 6 } ], (o) => o.a);
+index([{ a: 5 }, { a: 6 }], (o) => o.a);
 // @ts-expect-error
 index({ a: 6 }, 'a');