From 8c714d420fa4b16d8b92f35b06dfcaffe524be55 Mon Sep 17 00:00:00 2001
From: Martin Hochel <martinhochel@microsoft.com>
Date: Wed, 16 Jun 2021 14:41:24 +0200
Subject: [PATCH] test(tools): add docs for type utils and cover those utils by
 tests

---
 tools/types.spec.ts | 31 ++++++++++++++++++++++++++++++
 tools/types.ts      | 46 +++++++++++++++++++++++++++++++++++++--------
 2 files changed, 69 insertions(+), 8 deletions(-)
 create mode 100644 tools/types.spec.ts

diff --git a/tools/types.spec.ts b/tools/types.spec.ts
new file mode 100644
index 00000000000000..e8c1a78735683d
--- /dev/null
+++ b/tools/types.spec.ts
@@ -0,0 +1,31 @@
+import { KnownKeys, RemoveRecordIndexSignature } from './types';
+
+describe(`types`, () => {
+  describe(`utils`, () => {
+    describe(`#KnownKeys`, () => {
+      it(`should get keys from record except index signatures`, () => {
+        type RecordWithIndexType = { one: number; two: string; [k: string]: unknown };
+
+        // $ExpectType 'one' | 'two'
+        type Test = KnownKeys<RecordWithIndexType>;
+
+        // @ts-expect-error - testing types
+        const assertion: Test = 'random';
+        expect(assertion).toBeDefined();
+      });
+    });
+
+    describe(`#RemoveRecordIndexSignature`, () => {
+      it(`it should get record shape without index signatures`, () => {
+        type RecordWithIndexType = { one: number; two: string; [k: string]: unknown };
+
+        // $ExpectType { one: number; two: string; }
+        type Test = RemoveRecordIndexSignature<RecordWithIndexType>;
+
+        // @ts-expect-error - testing types
+        const assertion: Test = { one: 1, two: '2', fooBar: true };
+        expect(assertion).toBeDefined();
+      });
+    });
+  });
+});
diff --git a/tools/types.ts b/tools/types.ts
index 8add9e60fed61c..07e73d2379da58 100644
--- a/tools/types.ts
+++ b/tools/types.ts
@@ -1,13 +1,9 @@
-type RemoveIndex<T extends Record<string, unknown>> = Pick<T, KnownKeys<T>>;
-type KnownKeys<T> = {
-  [K in keyof T]: string extends K ? never : number extends K ? never : K;
-} extends { [_ in keyof T]: infer U }
-  ? U
-  : never;
-
 type TsOriginalCompilerOptions = import('typescript').CompilerOptions;
 interface CompilerOptions
-  extends Omit<RemoveIndex<TsOriginalCompilerOptions>, 'module' | 'target' | 'jsx' | 'moduleResolution'> {
+  extends Omit<
+    RemoveRecordIndexSignature<TsOriginalCompilerOptions>,
+    'module' | 'target' | 'jsx' | 'moduleResolution'
+  > {
   module?: keyof typeof import('typescript').ModuleKind;
   target?: keyof typeof import('typescript').ScriptTarget;
   jsx?: 'none' | 'preserve' | 'react' | 'react-native' | 'react-jsx' | 'react-jsxdev';
@@ -32,3 +28,37 @@ export interface PackageJson {
   devDependencies?: Record<string, string>;
   peerDependencies?: Record<string, string>;
 }
+
+// ===============
+//  Type Utilities
+// ===============
+
+/**
+ * Removes index signature `[key:string]: any` from Dictionary/Record
+ *
+ * @example
+ *
+ * ```ts
+ * type MapWithIndexType = { one: number; two: string; [k: string]: any; }
+ * // $ExpectType { one: number; two: string; }
+ * type Test = RemoveRecordIndexSignature<MapWithIndexType>
+ * ```
+ */
+export type RemoveRecordIndexSignature<T extends Record<string, unknown>> = Pick<T, KnownKeys<T>>;
+
+/**
+ * Get proper known keys from object which contains index type `[key:string]: any`
+ *
+ * @example
+ *
+ * ```ts
+ * type MapWithIndexType = { one: number; two: string; [k: string]: any; }
+ * // $ExpectType 'one' | 'two'
+ * type Test = KnownKeys<MapWithIndexType>
+ * ```
+ */
+export type KnownKeys<T> = {
+  [K in keyof T]: string extends K ? never : number extends K ? never : K;
+} extends { [_ in keyof T]: infer U }
+  ? U
+  : never;