feat(util): add helper for function parameter validation

Ovidiu Barabula · Ovidiu Barabula · commit c3e134e6bd3b · 2018-03-26T11:12:01.000+03:00
diff --git a/src/util/utility-functions.spec.ts b/src/util/utility-functions.spec.ts
@@ -5,7 +5,16 @@ chai.use(chaiAsPromised);
 import { assert, expect } from 'chai';
 import 'mocha';
 import { stdout } from 'test-console';
-import { ERRORS, getFnName, hasNested, limitFn, range, retry, sleep } from './utility-functions';
+import {
+  ERRORS,
+  getFnName,
+  hasNested,
+  limitFn,
+  range,
+  required,
+  retry,
+  sleep,
+} from './utility-functions';
 
 describe('Utility Functions', () => {
   describe('hasNested()', () => {
@@ -319,4 +328,21 @@ describe('Utility Functions', () => {
       }).timeout(5000);
     });
   });
+
+
+  describe('required()', () => {
+    it('throws an error with custom message when called', () => {
+      assert.throws(() => required('My custom error message'), 'My custom error message');
+    });
+
+
+    it('throws when called without <message> parameter', () => {
+      assert.throws(() => required(), ERRORS.REQUIRED_NEEDS_MESSAGE);
+    });
+
+
+    it('throws when called with non-string <message> parameter', () => {
+      assert.throws(() => required(1), ERRORS.REQUIRED_NEEDS_MESSAGE);
+    });
+  });
 });
diff --git a/src/util/utility-functions.ts b/src/util/utility-functions.ts
@@ -33,6 +33,9 @@ export const ERRORS = {
   RETRY_NEEDS_A_FUNCTION: 'retry() requires first argument <fn> to be of type \'function\'',
   RETRY_NEEDS_OPTIONS_TO_BE_OBJECT: 'retry() requires second argument <options> to be of type \'object\'',
   RETRY_RETRIES_CANNOT_BE_ZERO: 'retry() option <retries> cannot be 0',
+
+  // required()
+  REQUIRED_NEEDS_MESSAGE: 'required() requires first argument <message> of type \'string\'',
 };
 
 
@@ -246,3 +249,19 @@ export async function retry(
     return reject(errors[errors.length - 1]);
   });
 }
+
+
+/**
+ * Helper for function parameter validation
+ * This is useful for function parameter validation by assigning it as a default value
+ * If no value will be passed the function will be called automatically
+ * Usage: function foo(bar = required('<bar> is required')) { ... }
+ * @param message Custom error message
+ */
+export function required<T>(message: string): T {
+  if (typeof message === 'undefined' || typeof message !== 'string') {
+    throw new Error(ERRORS.REQUIRED_NEEDS_MESSAGE);
+  }
+
+  throw new Error(message);
+}
diff --git a/types/util/utility-functions.d.ts b/types/util/utility-functions.d.ts
@@ -14,6 +14,7 @@ export declare const ERRORS: {
     RETRY_NEEDS_A_FUNCTION: string;
     RETRY_NEEDS_OPTIONS_TO_BE_OBJECT: string;
     RETRY_RETRIES_CANNOT_BE_ZERO: string;
+    REQUIRED_NEEDS_MESSAGE: string;
 };
 /**
  * Check object for path
@@ -55,3 +56,11 @@ export declare function retry(fn: AnyFunction, options?: {
     logChannel?: string;
     logNamespace?: string;
 }): Promise<any>;
+/**
+ * Helper for function parameter validation
+ * This is useful for function parameter validation by assigning it as a default value
+ * If no value will be passed the function will be called automatically
+ * Usage: function foo(bar = required('<bar> is required')) { ... }
+ * @param message Custom error message
+ */
+export declare function required<T>(message: string): T;
