SyntaxError：当节点模块被忽略时，无法在模块 Jest 之外使用导入语句

Question

在使用 Jest 进行单元测试时获取 SyntaxError: Cannot use import statement outside a module。错误来自node-fetch 包，即required 包jsdom-worker。这可能是node-fetch 包的问题，​​但不完全确定。

我在jest.config.js 中忽略了节点模块，为什么这是个问题？

jest.config.js 文件：

const ignores = ['/node_modules/', '/__fixtures__/', '/fixtures/', '/__tests__/helpers/', '/__tests__/utils/', '__mocks__'];

module.exports = {
    preset: 'ts-jest',
    roots: ['<rootDir>'],
    modulePaths: [
        "<rootDir>/src"
    ],
    moduleDirectories: [
        "node_modules"
    ],
    transformIgnorePatterns: [...ignores],
    transform: {
        '^.+\\.(ts|tsx|js|jsx)?$': 'ts-jest',
        '^.+\\.(gif|svg|ico)$': '<rootDir>/svgTransform.js',
    },
    testRegex: '(/__tests__/.*|(\\.|/)(test|spec))\\.js?$',
    moduleFileExtensions: ['tsx', 'js', 'json', 'node', 'ts'],
    moduleNameMapper: {
        "\\.(css|less|scss|sass)$": "identity-obj-proxy"
      },
    clearMocks: true,
    // collectCoverage: true, // todo
    // coverageDirectory: "coverage",  // todo
    testEnvironment: 'jsdom',
    setupFilesAfterEnv: ['@testing-library/jest-dom/extend-expect', 'jsdom-worker'],
}
// }

更新：将node-fetch 降级到 2.4 版后，那错误消失了，但现在与另一个包有相同的语法问题，为什么会继续发生这种情况？

代码跟踪

babel.config.js

// Need to convert modules to commonjs format so Jest can undertstand them.
const isTest = String(process.env.NODE_ENV) === 'test'
const isProd = String(process.env.NODE_ENV) === 'production'

module.exports = {
    // For transformation of TSX and other react related bable plugins
    presets: [
        // Allows smart transpilation according to target environments
        ['@babel/preset-env', { modules: isTest ? 'commonjs' : false }],
        // Enabling Babel to understand TypeScript
        '@babel/preset-typescript',
    ],
}

也试过this来自 kcd-scripts 的 babel 配置：

"use strict";

const browserslist = require('browserslist');

const semver = require('semver');

const {
  ifDep,
  ifAnyDep,
  ifTypescript,
  parseEnv,
  appDirectory,
  pkg
} = require('../utils');

const {
  BABEL_ENV,
  NODE_ENV,
  BUILD_FORMAT
} = process.env;
const isTest = (BABEL_ENV || NODE_ENV) === 'test';
const isPreact = parseEnv('BUILD_PREACT', false);
const isRollup = parseEnv('BUILD_ROLLUP', false);
const isUMD = BUILD_FORMAT === 'umd';
const isCJS = BUILD_FORMAT === 'cjs';
const isWebpack = parseEnv('BUILD_WEBPACK', false);
const isMinify = parseEnv('BUILD_MINIFY', false);
const treeshake = parseEnv('BUILD_TREESHAKE', isRollup || isWebpack);
const alias = parseEnv('BUILD_ALIAS', isPreact ? {
  react: 'preact'
} : null);
const hasBabelRuntimeDep = Boolean(pkg.dependencies && pkg.dependencies['@babel/runtime']);
const RUNTIME_HELPERS_WARN = 'You should add @babel/runtime as dependency to your package. It will allow reusing "babel helpers" from node_modules rather than bundling their copies into your files.';

if (!treeshake && !hasBabelRuntimeDep && !isTest) {
  throw new Error(RUNTIME_HELPERS_WARN);
} else if (treeshake && !isUMD && !hasBabelRuntimeDep) {
  console.warn(RUNTIME_HELPERS_WARN);
}
/**
 * use the strategy declared by browserslist to load browsers configuration.
 * fallback to the default if don't found custom configuration
 * @see https://github.com/browserslist/browserslist/blob/master/node.js#L139
 */


const browsersConfig = browserslist.loadConfig({
  path: appDirectory
}) || ['defaults'];
const envTargets = isTest ? {
  node: 'current'
} : isWebpack || isRollup ? {
  browsers: browsersConfig
} : {
  node: getNodeVersion(pkg)
};
const envOptions = {
  modules: false,
  loose: true,
  targets: envTargets
};

module.exports = () => ({
  presets: [[require.resolve('@babel/preset-env'), envOptions], ifAnyDep(['react', 'preact'], [require.resolve('@babel/preset-react'), {
    pragma: isPreact ? ifDep('react', 'React.h', 'h') : undefined
  }]), ifTypescript([require.resolve('@babel/preset-typescript')])].filter(Boolean),
  plugins: [[require.resolve('@babel/plugin-transform-runtime'), {
    useESModules: treeshake && !isCJS
  }], require.resolve('babel-plugin-macros'), alias ? [require.resolve('babel-plugin-module-resolver'), {
    root: ['./src'],
    alias
  }] : null, ifAnyDep(['react', 'preact'], [require.resolve('babel-plugin-transform-react-remove-prop-types'), isPreact ? {
    removeImport: true
  } : {
    mode: 'unsafe-wrap'
  }]), isUMD ? require.resolve('babel-plugin-transform-inline-environment-variables') : null, [require.resolve('@babel/plugin-proposal-class-properties'), {
    loose: true
  }], isMinify ? require.resolve('babel-plugin-minify-dead-code-elimination') : null, treeshake ? null : require.resolve('@babel/plugin-transform-modules-commonjs')].filter(Boolean)
});

function getNodeVersion({
  engines: {
    node: nodeVersion = '10.13'
  } = {}
}) {
  const oldestVersion = semver.validRange(nodeVersion).replace(/[>=<|]/g, ' ').split(' ').filter(Boolean).sort(semver.compare)[0];

  if (!oldestVersion) {
    throw new Error(`Unable to determine the oldest version in the range in your package.json at engines.node: "${nodeVersion}". Please attempt to make it less ambiguous.`);
  }

  return oldestVersion;
}

Answer 1

通过安装包jest-webpack-resolver 并添加解决了这个问题

 "jestWebpackResolver": {
        "webpackConfig": "./webpack.config.js"
    },

给我的package.json。

Answer 2

我将我的 jest 配置重新配置为此，还需要模拟引发大多数错误的包：

module.exports = {
    roots: ['<rootDir>'],
    modulePaths: ['<rootDir>/src'],
    moduleDirectories: ['node_modules'],
    transformIgnorePatterns: ['/node_modules/'],
    transform: {
        '^.+\.(ts|tsx|js|jsx)?$': 'babel-jest',
        '^.+\.(jpg|jpeg|png|gif|svg|ico|url)$':
            '<rootDir>/src/__tests__/__utils__/imageTransform.js',
    },
    testRegex: '(/__tests__/.*|(\.|/)(test|spec))\.js?$',

    testPathIgnorePatterns: ['/__utils__/'],
    moduleFileExtensions: ['tsx', 'js', 'ts'],
    moduleNameMapper: {
        '\.(css|less|scss|sass)$': 'identity-obj-proxy',
        '\.(png|jpg|webp|ttf|woff|woff2|svg|mp4)$':
            '<rootDir>/src/__mocks__/fileMock.js',
    },
    clearMocks: true,
    setupFilesAfterEnv: [
        '@testing-library/jest-dom/extend-expect',
        './src/__tests__/__utils__/setup.js',
    ],
    testEnvironment: 'jsdom',
    collectCoverageFrom: ['src/**/*.{ts,tsx}', '!src/tests'],
}

模拟很简单：

module.exports = {
    nanoid: () =>
        Array(100)
            .fill()
            .map(() => Math.random())
            .join(''),
}

用于根级别 __mocks__ 文件中的 nanoid。