使用带有 lit-html 的打字稿编写测试时出现“语法错误:无法在模块外使用 import 语句”
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【中文标题】使用带有 lit-html 的打字稿编写测试时出现“语法错误:无法在模块外使用 import 语句”【英文标题】:"SyntaxError: Cannot use import statement outside a module" when writing test with typescript with lit-html 【发布时间】:2020-09-23 18:55:05 【问题描述】:我用打字稿写了一个简单的demo 用lit-html:
import html, TemplateResult from 'lit-html';
export default function sayHello(name: string): TemplateResult
return html`<h1>Hello $name</h1>`;
并用 jest 写一些简单的测试:
import sayHello from "./sayHello";
import render from "lit-html";
beforeEach(() =>
render('', document.body);
)
describe('sayHello', () =>
it('says hello', () =>
render(sayHello('world'), document.body);
const component = document.querySelector('h1');
expect(component).toBeDefined();
)
)
我的“jest.config.js”是:
module.exports =
preset: 'ts-jest',
testEnvironment: 'jsdom',
但是当我使用jest
运行测试时,我得到了这样的错误:
FAIL src/sayHello.test.ts
● Test suite failed to run
Jest encountered an unexpected token
This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain javascript.
By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".
Here's what you can do:
• To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
• If you need a custom transformation specify a "transform" option in your config.
• If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.
You'll find more details and examples of these config options in the docs:
https://jestjs.io/docs/en/configuration.html
Details:
/workspace/typescript-webpack-lit-html-jest-test-demo/node_modules/lit-html/lit-html.js:31
import defaultTemplateProcessor from './lib/default-template-processor.js';
^^^^^^
SyntaxError: Cannot use import statement outside a module
> 1 | import html, TemplateResult from 'lit-html';
| ^
2 |
3 | export default function sayHello(name: string): TemplateResult
4 | return html`<h1>Hello $name</h1>`;
at Runtime._execModule (node_modules/jest-runtime/build/index.js:1166:56)
at Object.<anonymous> (src/sayHello.ts:1:1)
at Object.<anonymous> (src/sayHello.test.ts:1:1)
Test Suites: 1 failed, 1 total
Tests: 0 total
Snapshots: 0 total
Time: 1.339 s
Ran all test suites.
error Command failed with exit code 1.
原因应该是“node_modules”node_modules/lit-html/lit-html.js
中的文件使用了es模块,jest处理不好。
我尝试了各种配置,但仍然无法修复,需要您的帮助,谢谢。
针对这个问题的一个小而完整的演示项目:https://github.com/freewind-demos/typescript-webpack-lit-html-jest-test-demo
【问题讨论】:
【参考方案1】:默认情况下,Jest 不会转换 /node_modules/
(docs)。为了使其正常工作,您可以像这样更改配置
点亮 2.0
还有@lit 命名空间包也需要转换:
@lit/reactive-element
所以在正则表达式中添加可选的@
就可以了
jest.config.js
module.exports =
// ...
transformIgnorePatterns: ["node_modules/(?!\@?lit)"],
working GitHub setup
ts-jest >27.x
config: 移除对 tsConfig 选项的支持 (#2127) (3cc9b80)
应使用小写tsconfig
而不是tsConfig
jest.config.js
module.exports =
preset: "ts-jest",
testEnvironment: "jsdom",
transform:
// transform files with ts-jest
"^.+\\.(js|ts)$": "ts-jest",
,
transformIgnorePatterns: [
// allow lit-html transformation
"node_modules/(?!lit-html)",
],
globals:
"ts-jest":
tsconfig:
// allow js in typescript
allowJs: true,
,
,
,
;
working GitHub setup (with "ts-jest": "27.0.3")
ts-jest
jest.config.js
module.exports =
preset: "ts-jest",
testEnvironment: "jsdom",
transform:
// transform files with ts-jest
"^.+\\.(js|ts)$": "ts-jest",
,
transformIgnorePatterns: [
// allow lit-html transformation
"node_modules/(?!lit-html)",
],
globals:
"ts-jest":
tsConfig:
// allow js in typescript
allowJs: true,
,
,
,
;
jest.config.js
module.exports =
preset: "ts-jest",
testEnvironment: "jsdom",
transform:
// transform files with ts-jest
"^.+\\.(js|ts)$": "ts-jest",
,
transformIgnorePatterns: [
// allow lit-html transformation
"node_modules/(?!lit-html)",
],
globals:
"ts-jest":
tsConfig:
// allow js in typescript
allowJs: true,
,
,
,
;
working GitHub setup(修复分支)
【讨论】:
谢谢!不幸的是,打字稿 4.3.3+ 似乎又出现了错误。 @jhorback 用最新版本的解决方案更新了我的答案 不适用于lit 嗨@Teneff,在您的仓库中,您使用的是已弃用的 lit-element。可以关注lit.dev/docs/releases/upgrade升级。 @leonheess 看看the lit branch以上是关于使用带有 lit-html 的打字稿编写测试时出现“语法错误:无法在模块外使用 import 语句”的主要内容,如果未能解决你的问题,请参考以下文章
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