Improve the type-utils package, split code, add some comments and examples

packages/blockchain-link/src/workers/electrum/index.ts

@@ -2,6 +2,7 @@ import { CustomError } from '@trezor/blockchain-link-types/src/constants/errors'
 import { MESSAGES, RESPONSES } from '@trezor/blockchain-link-types/src/constants';
 import type { Response } from '@trezor/blockchain-link-types';
 import { Message } from '@trezor/blockchain-link-types/src/messages';
+import { Without } from '@trezor/type-utils';
 
 import { BaseWorker, CONTEXT, ContextType } from '../baseWorker';
 import * as M from './methods';
@@ -13,9 +14,6 @@ import type { ElectrumClient } from './client/electrum';
 type BlockListener = ReturnType<typeof L.blockListener>;
 type TxListener = ReturnType<typeof L.txListener>;
 
-// reason:
-// https://stackoverflow.com/questions/57103834/typescript-omit-a-property-from-all-interfaces-in-a-union-but-keep-the-union-s#answer-57103940
-type Without<T, K extends keyof any> = T extends any ? Omit<T, K> : never;
 type Request<T> = T extends any
     ? T & ContextType<ElectrumClient> & { blockListener: BlockListener; txListener: TxListener }
     : never;

packages/type-utils/src/array.ts

@@ -0,0 +1,10 @@
+/**
+ * Gets the type of the elements in an array.
+ *
+ * Example:
+ *  ```
+ *  type A = (number | string)[];
+ *  type E = ArrayElement<A>; // number | string
+ *  ```
+ */
+export type ArrayElement<ArrayType extends readonly unknown[]> = ArrayType[number];

packages/type-utils/src/index.ts

@@ -1,2 +1,5 @@
-export * from './utils';
+export * from './array';
+export * from './overloads';
 export * from './timeout';
+export * from './utils';
+export * from './object';

packages/type-utils/src/object.ts

@@ -0,0 +1,13 @@
+export type GetObjectWithKey<U, K extends PropertyKey> = U extends object
+    ? K extends keyof U
+        ? U
+        : never
+    : never;
+
+export type GetObjectWithoutKey<U, K extends PropertyKey> = U extends object
+    ? K extends keyof U
+        ? never
+        : U
+    : never;
+
+export type ObjectsOnly<T> = T extends Record<string, unknown> ? T : never;