44 lines
1.2 KiB
TypeScript
44 lines
1.2 KiB
TypeScript
// Copyright 2017-2021 @polkadot/util authors & contributors
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// SPDX-License-Identifier: Apache-2.0
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import { isFunction } from './is/function';
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import { isUndefined } from './is/undefined';
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type MessageFn = () => string;
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/**
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* @name assert
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* @summary Checks for a valid test, if not Error is thrown.
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* @description
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* Checks that `test` is a truthy value. If value is falsy (`null`, `undefined`, `false`, ...), it throws an Error with the supplied `message`. When `test` passes, `true` is returned.
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* @example
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* <BR>
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*
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* ```javascript
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* const { assert } from '@polkadot/util';
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*
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* assert(true, 'True should be true'); // passes
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* assert(false, 'False should not be true'); // Error thrown
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* assert(false, () => 'message'); // Error with 'message'
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* ```
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*/
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export function assert (condition: unknown, message: string | MessageFn): asserts condition {
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if (!condition) {
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throw new Error(
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isFunction(message)
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? message()
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: message
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);
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}
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}
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/**
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* @name assertReturn
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* @summart Returns when the value is not undefined, otherwise throws assertion error
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*/
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export function assertReturn <T> (value: T | undefined, message: string | MessageFn): T {
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assert(!isUndefined(value), message);
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return value;
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}
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