Jest: Fails when testing modules that overrides require.extensions

[facundocabrera]

Hey all,

I'm trying to use Jest in replacement of plain jasmine for a small project and seems it's not playing well with code that uses require.extensions. I know it's deprecated, but the module node-jsx stills uses it internally https://github.com/petehunt/node-jsx/blob/master/index.js#L16

Any suggestion?

Thanks!

[cpojer]

Unfortunately we won't be able to support this natively anytime soon. I recommend moving away from require.extensions and using a preprocessor to do any kind of extra processing.

[kentcdodds]

I'm going to have to resurrect this and ask that you'd at least consider a pull request to make this happen. express-enrouten uses this as does babel-register.

In my particular case (with express-enrouten), all I need is for require.extensions to be: { js: function() { } }. It doesn't even need to actually be anything special. So even if I could stub this somehow myself, that'd be enough for me. Any ideas?

[cpojer]

The next version of Jest supports a "transforms" configuration option that you can use to run custom preprocessors on your files and wrap around babel-jest. That should also solve your problem.

[kentcdodds]

Awesome! So would this be correct?

const path = require('path')

module.exports = {
  process(src, filename, config, options) {
    return `
// a jest transform inserted this code:
require.extensions = [{js: function() {}}]
// end jest transform
${src}
    `
  },
  getCacheKey(fileData, filename, configString, options) {
    return filename
  },
}

And then configure it like so:

{
  "transform": {
    "regex-that-matches-filename": "<rootDir>/path-to-transformer.js"
  }
}

Is that correct?

Second question: How can I help get this released? This and #2048 are the only things left for my mocha to jest migration of my project's server tests. It's so close I can taste it.

[supasate]

I have the same issue with require.extensions. I tried with the same approach with @kentcdodds. My test file is transformed, however, the module that my test file depending on (in node_modules) is not transformed and that module uses require.extensions.

Is there any method to transform the code in node_modules? or did I do something wrong?

The followings are my config and preprocessor file:
My package.json

  "jest": {
    "verbose": true,
    "testEnvironment": "node",
    "transform": {
      "^.+\\.js$": "<rootDir>/preprocessor.js"
    }
  }

My preprocessor.js

module.exports = {
  process(src, path) {
    return `
require.extensions = [{ '.js': function () {} }]
${src}`
  },
}

[thymikee]

@supasate you can make use of transformIgnorePatterns. And another example from RN tutorial: http://facebook.github.io/jest/docs/tutorial-react-native.html#transformignorepatterns-customization

[supasate]

It works! My bad that I overlooked that option.
Thank you @thymikee!

[theoutlander]

@kentcdodds did you ever solve this issue? I just added server tests and noticed that enrouten is having issues around require.extensions. I tried modifying it before the test runs, but I think jest is overriding it or using mocks.

[kentcdodds]

Yes. My problem was also express-enrouten. The workaround I tried above worked. Here's what it looks like currently:

// this is here because enrouten uses require.extensions (something that was deprecated in Node v0.10.0) and Jest
// doesn't support that API. Basically this just sticks a mock to the top of the relevant file.
module.exports = {
  process(src, filename, config, options) {
    return `
// a jest transform inserted this code:
require.extensions = {'.js': function() {}};
// end jest transform
${src}
    `
  },
}

Then in my jest config:

"transform": {
  // other stuff
  "express-enrouten\\/lib\\/directory\\.js$":  "<rootDir>/tests/lib/enrouten-require-extensions-transform.js"
},

Good luck. :+1: