jest.preprocessor.js

// NOTE: Mini Dragons be here.
// This is a copy of /node_modules/react-native/jest/preprocess.js
// There is one difference, the `inlineRequires: true` is commented out below
// in the reactNativeTransformer options.
// We have to do this to make tests run after updating to RN 0.57.x
// Something in that broke the Jest/Babel/? setup and caused any code with
// class properties to fail to run.
//
// See: https://github.com/facebook/react-native/issues/22175#issuecomment-436959462
// TODO: Keep an eye on this and remove it as soon as there is a better fix
// available.

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 * @flow
 */

/* eslint-env node */

'use strict';

const { transformSync: babelTransformSync } = require('@babel/core');
/* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
 * found when Flow v0.54 was deployed. To see the error delete this comment and
 * run Flow. */
const babelRegisterOnly = require('metro-babel-register');
/* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
 * found when Flow v0.54 was deployed. To see the error delete this comment and
 * run Flow. */
const createCacheKeyFunction = require('fbjs-scripts/jest/createCacheKeyFunction');
const generate = require('@babel/generator').default;

const nodeFiles = new RegExp(
	[
		'/metro(?:-[^/]*)?/', // metro, metro-core, metro-source-map, metro-etc.
	].join('|'),
);

const nodeOptions = babelRegisterOnly.config([nodeFiles]);

babelRegisterOnly([]);

/* $FlowFixMe(site=react_native_oss) */
const transformer = require('metro-react-native-babel-transformer');
module.exports = {
	process(src /*: string */, file /*: string */) {
		if (nodeFiles.test(file)) {
			// node specific transforms only
			return babelTransformSync(src, {
				filename: file,
				sourceType: 'script',
				...nodeOptions,
				ast: false
			}).code;
		}

		const { ast } = transformer.transform({
			filename: file,
			options: {
				ast: true, // needed for open source (?) https://github.com/facebook/react-native/commit/f8d6b97140cffe8d18b2558f94570c8d1b410d5c#r28647044
				dev: true,
				enableBabelRuntime: false,
				experimentalImportSupport: false,
				hot: false,
				// NOTE: Commenting this line out allows our tests to run and pass
				// as expected.
				// See: https://github.com/facebook/react-native/issues/22175#issuecomment-436959462
				// inlineRequires: true,
				minify: false,
				platform: '',
				projectRoot: '',
				retainLines: true,
				sourceType: 'unambiguous' // b7 required. detects module vs script mode
			},
			src,
			plugins: [
				[require('@babel/plugin-transform-block-scoping')],
				// the flow strip types plugin must go BEFORE class properties!
				// there'll be a test case that fails if you don't.
				[require('@babel/plugin-transform-flow-strip-types')],
				[
					require('@babel/plugin-proposal-class-properties'),
					// use `this.foo = bar` instead of `this.defineProperty('foo', ...)`
					{ loose: true }
				],
				[require('@babel/plugin-transform-computed-properties')],
				[require('@babel/plugin-transform-destructuring')],
				[require('@babel/plugin-transform-function-name')],
				[require('@babel/plugin-transform-literals')],
				[require('@babel/plugin-transform-parameters')],
				[require('@babel/plugin-transform-shorthand-properties')],
				[require('@babel/plugin-transform-react-jsx')],
				[require('@babel/plugin-transform-regenerator')],
				[require('@babel/plugin-transform-sticky-regex')],
				[require('@babel/plugin-transform-unicode-regex')],
				[require('@babel/plugin-transform-modules-commonjs'), { strict: false, allowTopLevelThis: true }],
				[require('@babel/plugin-transform-classes')],
				[require('@babel/plugin-transform-arrow-functions')],
				[require('@babel/plugin-transform-spread')],
				[require('@babel/plugin-proposal-object-rest-spread')],
				[
					require('@babel/plugin-transform-template-literals'),
					{ loose: true } // dont 'a'.concat('b'), just use 'a'+'b'
				],
				[require('@babel/plugin-transform-exponentiation-operator')],
				[require('@babel/plugin-transform-object-assign')],
				[require('@babel/plugin-transform-for-of'), { loose: true }],
				[require('@babel/plugin-transform-react-display-name')],
				[require('@babel/plugin-transform-react-jsx-source')]
			]
		});

		return generate(
			ast,
			{
				code: true,
				comments: false,
				compact: false,
				filename: file,
				retainLines: true,
				sourceFileName: file,
				sourceMaps: true
			},
			src
		).code;
	},

	getCacheKey: createCacheKeyFunction([
		__filename,
		require.resolve('metro-react-native-babel-transformer'),
		require.resolve('@babel/core/package.json')
	])
};