Add NullOrAssert to allow any assert to be nullable

README.md

@@ -46,6 +46,7 @@ The following set of extra asserts are provided by this package:
 - [Iso3166Country](#iso3166country) (requires `isoc`)
 - [Json](#json)
 - [NotEmpty](#notempty)
+- [NullOr](#nullor)
 - [NullOrDate](#nullordate)
 - [NullOrBoolean](#nullorboolean)
 - [NullOrString](#nullorstring)
@@ -196,6 +197,9 @@ Tests if the value is valid json.
 ### NotEmpty
 Tests if the value is not an empty (empty object, empty array, empty string, etc).
 
+### NullOr
+Tests if the value is a `null` or validates agains the assert received as an argument.
+
 ### NullOrBoolean
 Tests if the value is a `null` or `boolean`.
 
@@ -264,6 +268,13 @@ if (true !== violation) {
   console.log('"foo" is not a valid IP. Violation:', violation[0].show());
   // => "foo" is not a valid IP. Violation: { assert: 'Ip', value: 'foo' }
 }
+
+// Make the validation nullable.
+violation = validator.validate(null, is.nullOr(is.ip()));
+
+if (true === violation) {
+  console.log('null is null or a valid IP'); // => null is null or a valid IP
+}
 ```
 
 ## Tests

src/asserts/null-or-assert.js

@@ -0,0 +1,41 @@
+'use strict';
+
+/**
+ * Export `NullOrAssert`.
+ */
+
+module.exports = function nullOrAssert(assert) {
+  /**
+   * Class name.
+   */
+
+  this.__class__ = 'NullOr';
+
+  if (typeof assert !== 'object') {
+    throw new Error('Assert must be an object.');
+  }
+
+  if (typeof assert.validate !== 'function') {
+    throw new Error('Assert must have a validate function.');
+  }
+
+  /**
+   * Nullable assert.
+   */
+
+  this.assert = assert;
+
+  /**
+   * Validation algorithm.
+   */
+
+  this.validate = value => {
+    if (value === null) {
+      return true;
+    }
+
+    return this.assert.validate(value);
+  };
+
+  return this;
+};

src/index.js

@@ -30,6 +30,7 @@ const Ip = require('./asserts/ip-assert.js');
 const Iso3166Country = require('./asserts/iso-3166-country-assert.js');
 const Json = require('./asserts/json-assert.js');
 const NotEmpty = require('./asserts/not-empty-assert.js');
+const NullOr = require('./asserts/null-or-assert.js');
 const NullOrBoolean = require('./asserts/null-or-boolean-assert.js');
 const NullOrDate = require('./asserts/null-or-date-assert.js');
 const NullOrString = require('./asserts/null-or-string-assert.js');
@@ -73,6 +74,7 @@ module.exports = {
   Iso3166Country,
   Json,
   NotEmpty,
+  NullOr,
   NullOrBoolean,
   NullOrDate,
   NullOrString,

test/asserts/null-or-assert.test.js

@@ -0,0 +1,100 @@
+'use strict';
+
+/**
+ * Module dependencies.
+ */
+
+const { Assert: BaseAssert, Violation } = require('validator.js');
+const NullOrAssert = require('../../src/asserts/null-or-assert');
+const UuidAssert = require('../../src/asserts/uuid-assert');
+
+/**
+ * Extend `Assert` with `NullOrAssert`.
+ */
+
+const Assert = BaseAssert.extend({
+  NullOr: NullOrAssert,
+  Uuid: UuidAssert
+});
+
+/**
+ * Test `NullOrAssert`.
+ */
+
+describe('NullOrAssert', () => {
+  it('should throw an error if the specified assert is missing', () => {
+    try {
+      Assert.nullOr('foo').validate();
+
+      fail();
+    } catch (e) {
+      expect(e).toBeInstanceOf(Error);
+      expect(e.message).toBe('Assert must be an object.');
+    }
+  });
+
+  it('should throw an error if the specified assert is not valid', () => {
+    try {
+      Assert.nullOr('foo').validate('bar');
+
+      fail();
+    } catch (e) {
+      expect(e).toBeInstanceOf(Error);
+      expect(e.message).toBe('Assert must be an object.');
+    }
+  });
+
+  it('should throw an error if the specified assert has no `validate` function', () => {
+    try {
+      Assert.nullOr({}).validate(123);
+
+      fail();
+    } catch (e) {
+      expect(e).toBeInstanceOf(Error);
+      expect(e.message).toBe('Assert must have a validate function.');
+    }
+  });
+
+  it('should throw an error if the specified assert has a `validate` property that is not a function', () => {
+    try {
+      Assert.nullOr({ validate: true }).validate(123);
+
+      fail();
+    } catch (e) {
+      expect(e).toBeInstanceOf(Error);
+      expect(e.message).toBe('Assert must have a validate function.');
+    }
+  });
+
+  it('should throw an error if the value is not null and is not valid for the specified assert', () => {
+    try {
+      Assert.nullOr(Assert.string()).validate(123);
+
+      fail();
+    } catch (e) {
+      expect(e).toBeInstanceOf(Violation);
+      expect(e.show().assert).toBe('IsString');
+      expect(e.violation.value).toBe('must_be_a_string');
+    }
+  });
+
+  it('should include the arguments of the specified assert', () => {
+    try {
+      Assert.nullOr(Assert.uuid(4)).validate('foobar');
+
+      fail();
+    } catch (e) {
+      expect(e).toBeInstanceOf(Object);
+      expect(e.show().assert).toBe('Uuid');
+      expect(e.violation.version).toBe(4);
+    }
+  });
+
+  it('should accept a null value', () => {
+    Assert.nullOr(Assert.string()).validate(null);
+  });
+
+  it('should accept a value that is valid for the specified assert', () => {
+    Assert.nullOr(Assert.string()).validate('foobar');
+  });
+});

test/index.test.js

@@ -14,7 +14,7 @@ describe('validator.js-asserts', () => {
   it('should export all asserts', () => {
     const assertNames = Object.keys(asserts);
 
-    expect(assertNames).toHaveLength(37);
+    expect(assertNames).toHaveLength(38);
     expect(assertNames).toEqual(
       expect.arrayContaining([
         'AbaRoutingNumber',
@@ -43,6 +43,7 @@ describe('validator.js-asserts', () => {
         'Iso3166Country',
         'Json',
         'NotEmpty',
+        'NullOr',
         'NullOrBoolean',
         'NullOrDate',
         'NullOrString',