feat: Add contains-substring filter for String fields

src/lib/Filters.js

@@ -64,6 +64,12 @@ export const Constraints = {
     composable: true,
     comparable: true,
   },
+  contains: {
+    name: 'contains substring',
+    field: 'String',
+    composable: true,
+    comparable: true,
+  },
   before: {
     name: 'is before',
     field: 'Date',
@@ -185,7 +191,18 @@ export const FieldConstraints = {
   Pointer: ['exists', 'dne', 'eq', 'neq', 'starts', 'containedIn', 'unique'],
   Boolean: ['exists', 'dne', 'eq', 'neq', 'containedIn', 'unique'],
   Number: ['exists', 'dne', 'eq', 'neq', 'lt', 'lte', 'gt', 'gte', 'containedIn', 'unique'],
-  String: ['exists', 'dne', 'eq', 'neq', 'starts', 'ends', 'matches', 'containedIn', 'unique'],
+  String: [
+    'exists',
+    'dne',
+    'eq',
+    'neq',
+    'starts',
+    'ends',
+    'matches',
+    'contains',
+    'containedIn',
+    'unique',
+  ],
   Date: [
     'exists',
     'dne',

src/lib/queryFromFilters.js

@@ -232,6 +232,9 @@ export function addConstraintFromValues(query, field, constraint, compareTo, mod
     case 'matches':
       query.matches(field, String(compareTo), modifiers);
       break;
+    case 'contains':
+      query.contains(field, String(compareTo));
+      break;
     case 'keyExists':
       query.exists(field + '.' + compareTo);
       break;

src/lib/tests/queryFromFilters.test.js

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2016-present, Parse, LLC
+ * All rights reserved.
+ *
+ * This source code is licensed under the license found in the LICENSE file in
+ * the root directory of this source tree.
+ */
+jest.dontMock('../queryFromFilters');
+
+const { addConstraintFromValues } = require('../queryFromFilters');
+const Parse = require('parse');
+
+function whereFor(field, constraint, compareTo, modifiers) {
+  const query = new Parse.Query('Test');
+  addConstraintFromValues(query, field, constraint, compareTo, modifiers);
+  return query.toJSON().where;
+}
+
+describe('addConstraintFromValues contains constraint', () => {
+  it('matches a plain substring literally', () => {
+    expect(whereFor('name', 'contains', 'foo')).toEqual({
+      name: { $regex: '\\Qfoo\\E' },
+    });
+  });
+
+  it('escapes regex metacharacters so they match literally', () => {
+    expect(whereFor('name', 'contains', 'a.b(c)')).toEqual({
+      name: { $regex: '\\Qa.b(c)\\E' },
+    });
+  });
+
+  it('keeps matches as a raw, unescaped regex with modifiers', () => {
+    expect(whereFor('name', 'matches', 'a.b(c)', 'i')).toEqual({
+      name: { $regex: 'a.b(c)', $options: 'i' },
+    });
+  });
+});