Testing npm packages before publishing

https://blog.vcarl.com/testing-packages-before-publishing/
Now, I use npm pack.

npm pack

The pack command creates a .tgz file exactly the way it would if you were going to publish the package to npm. It pulls the name and version from package.json, resulting in a file like package-name-0.0.0.tgz. This can be copied, uploaded, or sent to a coworker. It's exactly the file that would be uploaded to npm if you published it.

~/workspace/package-name $ npm pack

Once you have the file, you can install it. npm install can install from a lot more sources than just npm, and I highly suggest skimming through the docs. We have to specify the full path to the file, so I usually copy it to my home directory first for convenience.

~/workspace/package-name $ npm pack
~/workspace/package-name $ cp package-name-0.0.0.tgz ~
~/workspace/some-application $ npm install ~/package-name-0.0.0.tgz

You could probably set up an alias or function in your terminal to automate this, but I don't do it frequently enough to bother. npm pack | tail -n 1 will output just the filename to standard out.

This runs through a complete publish cycle—it even runs the publish npm script and the associated pre-scripts and post-scripts. Packing it up and installing it is an excellent way to simulate publishing a package, and it avoids all of the quirks and problems of symlinking.

I know when I was first trying to publish packages to npm, one of the hurdles I faced was figuring out if it would actually work. Publishing feels so final; you put it up for the world to see and that version number can never be used again. npm pack helps me be more confident that it's going to work the way I expect it to.

实战

我们从零构建一个项目，用来测试一个名为structural-comparison的npm包。

打包npm包的tgz压缩文件

开始建立测试项目前，在主包的位置，运行命令行，生成当地tgz文件。

structural-comparison $ npm pack

此命令会在structural-comparison文件夹生成一个压缩文件，名为structural-comparison-1.1.0.tgz。

初始化测试项目

在你希望的位置建立一个文件夹，名为structural-comparison-test。

在structural-comparison-test根目录下，使用package.json配置项目，其内容为：

{
  "dependencies": {
  },
  "devDependencies": {
    "@babel/core": "7.15.8",
    "@babel/preset-env": "7.15.8",
    "babel-loader": "8.2.3",
    "core-js": "3.18.3",
    "jest": "27.3.1"
  },
  "scripts": {
    "test": "jest"
  },
  "name": "structural-comparison-test",
  "private": true,
  "license": "LGPL-3.0-or-later"
}

注："name"，"private"，"license"字段是安装本地tgz包必须的字段，尽管它们似乎没有用处。

命令行，执行安装程序。

structural-comparison-test $ npm i

安装本地tgz包到测试项目

在测试项目根目录的命令行，执行安装程序。

structural-comparison-test $ npm install .../structural-comparison/structural-comparison-1.1.0.tgz

给出的文件来源参数用了省略号，实际上键入的是文件绝对路径。一个小技巧，我们可以用鼠标拖动tgz文件，释放到当前命令行，即可代替手动打字，生成文件的绝对路径。

命令执行完成，重新用编辑器打开package.json文件查看。

{
  "dependencies": {
    "structural-comparison": "file:../../../../structural-comparison/structural-comparison-1.1.0.tgz"
  },
}

"file:"是本地文件安装包的前缀。这是因为，npm i命令中的文件路径 will be normalized to a relative path and added to your package.json.

验证

另外，再配置好babel，如果需要的话。

我们添加一个使用structural-comparison项目的测试文件：

import { thunk } from 'structural-comparison'

test('thunk test', () => {
    let lazyadd = thunk((a, b) => a + b)
    let y = lazyadd(1, 2)()
    expect(y).toEqual(3)
})

命令行执行测试命令：

structural-comparison-test $ npm test

如果正常运行，说明测试项目已经正确依赖了npm项目的本地包。

更新

当我们修改了本地包，需要更新测试项目中安装的包，只需再次执行安装命令。并且无需更改版本号，本地包将自动更新。

structural-comparison-test $ npm install .../structural-comparison/structural-comparison-1.1.0.tgz

执行命令最后的总结是移出了一个包，并添加了一个包。

当更新.tgz文件后，执行npm i是否会自动更新包，我还没有尝试，等有机会再来尝试补充。