babel-jest issues with monorepo and jest multi project runner

🐛 Bug Report

We are moving to a monorepo structure, and we’d like to use jest multi-project-runner structure. We are using yarn workspaces and lerna to manage dependencies. Here is a repro https://github.com/entria/entria-fullstack/pull/12, where you can reproduce some of the issues.

To Reproduce

Neither of this transforms works:

'^.+\\.(js|ts|tsx)?$': 'babel-jest',

^.+\\.(js|ts|tsx)?$': '<rootDir>/node_modules/babel-jest',

I think the problem here is that babel-jest resolution strategy is failing to find the correct babel.config.js file

Only creating a custom babel transformer the transform works, like the below:

const config = require('../babel.config');
 const { createTransformer } = require('babel-jest');
 module.exports = createTransformer({
  ...config,
});

Steps to reproduce the behavior: Run jest on root of this project https://github.com/entria/entria-fullstack/pull/12

modify transform config from custom transformer to babel-jest

Another problem is that when using only projects option on jest.config.js root, it won’t use a different jest config per project, it is looks like all the config should be on root jest.config.js instead of jest.config.js inside each project

Expected behavior

• it should find correct babel.config.js

• it should transpile all files inside packages/*

• it should use the jest.config.js for each project (transform options and so on)

Link to repl or repo (highly encouraged)

https://github.com/entria/entria-fullstack/pull/12

Run npx envinfo --preset jest

Paste the results here:

System:
    OS: macOS 10.14.1
    CPU: (4) x64 Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
  Binaries:
    Node: 10.12.0 - ~/.nvm/versions/node/v10.12.0/bin/node
    Yarn: 1.12.3 - /usr/local/bin/yarn
    npm: 6.4.1 - ~/.nvm/versions/node/v10.12.0/bin/npm
  npmPackages:
    jest: ^23.6.0 => 23.6.0 

[ofhouse]

I am using jest multi project runner with babel-jest and it works just fine. Each package in the monorepo has it’s own local .babelrc.js and no .babelrc.js in the root is required.

Each of my packages has a jest.config.js with the following settings to make this work:

module.exports = {
  ...
  transform: {
    '\\.js$': ['babel-jest', { cwd: __dirname }],
  },
  ...
};

I made an example repo which contains two packages with different babel-configs, feel free to check it out: https://github.com/ofhouse/jest-project-babel-transformer

Edit: You need Jest >= 24.9.0 to pass options to transformers

[bobbybobby]

@bradfordlemley said

What if users want top-level babel config?: If individual projects want to include top-level babel config, it can be achieved by configuring babel to rootMode upward or whatever is desired. Currently, that configuration would need to be set in a custom jest transform module, but #7288 adds the ability to configure babel-jest within jest’s config, so that will hopefully become easier. This way, the top-level babel.config.js would apply if the project is run individually or via multi-project.

Here’s how I configured it in my monorepo project (that uses yarn workspaces for dependency management, and lerna for running commands on sub packages).

Project structure :

/monorepo
  babel.config.js
    /packages/
      /pkg1
        jest.config.js
        jestBabelTransform.js
        ...

/babel.config.js :

module.exports = {
  presets: [ "@babel/env", "@babel/react" ],
  babelrcRoots: ["./packages/*"]
};

/packages/pkg1/jest.config.js :

const path = require('path');

module.exports = {
  transform: {
    "^.+\\.js$": path.resolve(__dirname, "./jestBabelTransform.js")
  },
};

/packages/pkg1/jestBabelTransform.js :

const babelJest = require('babel-jest');

module.exports = babelJest.createTransformer({
  rootMode: 'upward'
});

I’m already using the rootMode: upward option with my build process, this way I get the same behaviour running jest. I can run jest from the pkg1 directory with yarn test or from the monorepo root with lerna run test --scope pkg1.