test(tools): add docs for type utils and cover those utils by tests

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();
+      });
+    });
+  });
+});

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;