feat(micro-dash): improve typing of forEach

Closes #22
simontonsoftware · Feb 3, 2021 · 74dbdbf · 74dbdbf
1 parent 4b1aad6
commit 74dbdbf
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Showing 2 changed files with 117 additions and 6 deletions.
diff --git a/projects/micro-dash/src/lib/collection/for-each.ts b/projects/micro-dash/src/lib/collection/for-each.ts
@@ -1,4 +1,4 @@
-import { ArrayIteratee, ObjectIteratee } from '../interfaces';
+import { ArrayIteratee, Nil, ObjectIteratee } from '../interfaces';
 import { forOwnOfNonArray } from '../object/for-own';
 
 /**
@@ -9,13 +9,13 @@ import { forOwnOfNonArray } from '../object/for-own';
  * - Micro-dash: 236 bytes
  */
 
-export function forEach<T>(
-  array: T[] | undefined,
-  iteratee: ArrayIteratee<T, void | boolean>,
-): T[];
+export function forEach<T extends any[] | Nil>(
+  array: T,
+  iteratee: ArrayIteratee<NonNullable<T>[number], void | boolean>,
+): T;
 export function forEach<T>(
   object: T,
-  iteratee: ObjectIteratee<T, void | boolean>,
+  iteratee: ObjectIteratee<NonNullable<T>, void | boolean>,
 ): T;
 
 export function forEach(collection: any, iteratee: any): any {

diff --git a/projects/micro-dash/src/typing-tests/collection/for-each.dts-spec.ts b/projects/micro-dash/src/typing-tests/collection/for-each.dts-spec.ts
@@ -0,0 +1,111 @@
+import { forEach } from '../../lib/collection';
+
+interface Obj {
+  a: 1;
+  b: string;
+}
+
+declare const array: number[];
+declare const arrayOrN: number[] | null;
+declare const arrayOrU: number[] | undefined;
+
+// $ExpectType number[]
+forEach(
+  array,
+  (
+    // $ExpectType number
+    val,
+    // $ExpectType number
+    index,
+  ) => {},
+);
+// $ExpectType number[] | null
+forEach(
+  arrayOrN,
+  (
+    // $ExpectType number
+    val,
+    // $ExpectType number
+    index,
+  ) => {},
+);
+// $ExpectType number[] | undefined
+forEach(
+  arrayOrU,
+  (
+    // $ExpectType number
+    val,
+    // $ExpectType number
+    index,
+  ) => {},
+);
+
+declare const tuple: [string, Date];
+declare const tupleOrN: [string, Date] | null;
+declare const tupleOrU: [string, Date] | undefined;
+
+// $ExpectType [string, Date]
+forEach(
+  tuple,
+  (
+    // $ExpectType string | Date
+    val,
+    // $ExpectType number
+    index,
+  ) => {},
+);
+// $ExpectType [string, Date] | null
+forEach(
+  tupleOrN,
+  (
+    // $ExpectType string | Date
+    val,
+    // $ExpectType number
+    index,
+  ) => {},
+);
+// $ExpectType [string, Date] | undefined
+forEach(
+  tupleOrU,
+  (
+    // $ExpectType string | Date
+    val,
+    // $ExpectType number
+    index,
+  ) => {},
+);
+
+declare const obj: Obj;
+declare const objOrN: Obj | null;
+declare const objOrU: Obj | undefined;
+
+// $ExpectType Obj
+forEach(
+  obj,
+  (
+    // $ExpectType string | 1
+    val,
+    // $ExpectType "a" | "b"
+    key,
+  ) => {},
+);
+// $ExpectType Obj | null
+forEach(
+  objOrN,
+  (
+    // $ExpectType string | 1
+    val,
+    // $ExpectType "a" | "b"
+    key,
+  ) => {},
+);
+// $ExpectType Obj | undefined
+forEach(
+  objOrU,
+  (
+    // $ExpectType string | 1
+    val,
+    // $ExpectType "a" | "b"
+    key,
+  ) => {},
+);