Add a gulp script for extracting error codes (#6882)

scripts/error-codes/__tests__/evalToString-test.js

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+var evalToString = require('../evalToString');
+var babylon = require('babylon');
+
+var parse = (source) => babylon.parse(
+  `(${source});`
+).program.body[0].expression; // quick way to get an exp node
+
+var parseAndEval = (source) => evalToString(parse(source));
+
+describe('evalToString', () => {
+  it('should support StringLiteral', () => {
+    expect(parseAndEval(`'foobar'`)).toBe('foobar');
+    expect(parseAndEval(`'yowassup'`)).toBe('yowassup');
+  });
+
+  it('should support string concat (`+`)', () => {
+    expect(parseAndEval(`'foo ' + 'bar'`)).toBe('foo bar');
+  });
+
+  it('should throw when it finds other types', () => {
+    expect(() => parseAndEval(`'foo ' + true`)).toThrowError(/Unsupported type/);
+    expect(() => parseAndEval(`'foo ' + 3`)).toThrowError(/Unsupported type/);
+    expect(() => parseAndEval(`'foo ' + null`)).toThrowError(/Unsupported type/);
+    expect(() => parseAndEval(`'foo ' + undefined`)).toThrowError(/Unsupported type/);
+  });
+});