feat: add field option type: "null"

Author: jalik

src/checks.ts

@@ -55,6 +55,7 @@ export type FieldType =
   | 'boolean'
   | 'function' // todo remove in v5
   | 'integer'
+  | 'null'
   | 'number'
   | 'object'
   | 'string'
@@ -499,7 +500,7 @@ export function checkRequired (required: boolean, value: any, label: string, pat
  */
 export function checkType (
   type: FieldType,
-  value: any[] | boolean | number | object | string | ((...args: any[]) => void),
+  value: any[] | boolean | null | number | object | string | ((...args: any[]) => void),
   label: string,
   path: string
 ): void {
@@ -525,6 +526,11 @@ export function checkType (
           throw new FieldTypeError(label, type, path)
         }
         break
+      case 'null':
+        if (value !== null) {
+          throw new FieldTypeError(label, type, path)
+        }
+        break
       case 'number':
         if (typeof value !== 'number' || Number.isNaN(value)) {
           throw new FieldTypeError(label, type, path)

test/SchemaField.test.ts

@@ -267,14 +267,19 @@ describe('SchemaField', () => {
   })
 
   describe('getType()', () => {
-    describe('with type: String', () => {
-      it('should return a string', () => {
-        const field = new SchemaField('field', { type: 'string' })
-        expect(field.getType()).toBe('string')
+    describe('with type defined', () => {
+      it('should return the type', () => {
+        expect(new SchemaField('field', { type: 'array' }).getType()).toBe('array')
+        expect(new SchemaField('field', { type: 'boolean' }).getType()).toBe('boolean')
+        expect(new SchemaField('field', { type: 'integer' }).getType()).toBe('integer')
+        expect(new SchemaField('field', { type: 'null' }).getType()).toBe('null')
+        expect(new SchemaField('field', { type: 'number' }).getType()).toBe('number')
+        expect(new SchemaField('field', { type: 'object' }).getType()).toBe('object')
+        expect(new SchemaField('field', { type: 'string' }).getType()).toBe('string')
       })
     })
 
-    describe('with type: undefined', () => {
+    describe('with type undefined', () => {
       it('should return undefined', () => {
         const field = new SchemaField('field', {})
         expect(field.getType()).toBeUndefined()

test/checks.test.ts

@@ -1,11 +1,12 @@
 /*
  * The MIT License (MIT)
- * Copyright (c) 2023 Karl STEIN
+ * Copyright (c) 2024 Karl STEIN
  */
 
 import { describe, expect, it } from '@jest/globals'
-import { checkAllowed } from '../src/checks'
+import { checkAllowed, checkType } from '../src/checks'
 import FieldAllowedError from '../src/errors/FieldAllowedError'
+import FieldTypeError from '../src/errors/FieldTypeError'
 
 describe('checkAllowed', () => {
   describe('with value allowed', () => {
@@ -23,3 +24,22 @@ describe('checkAllowed', () => {
     })
   })
 })
+
+describe('checkType', () => {
+  describe('with type = "null"', () => {
+    describe('with value = null', () => {
+      it('should not throw an Error', () => {
+        expect(() => {
+          checkType('null', null, 'field', 'field')
+        }).not.toThrow()
+      })
+    })
+    describe('with value !== null', () => {
+      it('should throw a FieldTypeError', () => {
+        expect(() => {
+          checkType('null', 'null', 'field', 'field')
+        }).toThrow(FieldTypeError)
+      })
+    })
+  })
+})