Default to using require to find 'eslint' if the module isn't found in the test directory

[AndrewFinlay]

Hi there,

I'd like the runner to be able to find the eslint module in a path relative to the runner, or one that has been installed globally.

Currently the runner imports eslint according to the rules in getLocalESLint. This function finds the first node_modules directory up from the <rootDir> then tries to require eslint from it, regardless of whether the package exists there or not.

Would it be possible to provide a fallback require in case this fails?

The new method would search for 'node_modules/eslint' in the findUp, then if that fails to find a path, try to import the module with a plain old require('eslint'). This will prefer existing versions of eslint in the test directory, and default to an eslint that can be found using the standard require call.

Can submit a PR if req'd

[ljharb]

Related to #35.

Note that a normal require does not find eslint in the PATH, it only finds it in a node_modules folder (what findUp is doing).

It sounds like you’re just asking the findUp to start lower than the root dir - can you elaborate on your use case where you have a nested node_modules?

[AndrewFinlay]

In my particular use case, I have a side by side folder structure as shown below. In this structure there is a single eslint module in the node_modules of test-tools.

Apps
  ├── test-tools
  |       ├── lib
  |       └── node_modules
  |               ├── eslint
  |               ├── jest
  |               ├── jest-runner-eslint
  |               └── ...
  ├── project-one
  |       ├── lib
  |       └── node_modules
  |       |       └── ...
  |       └── jest.config.js

If I want to run tests over a single project, say with <rootDir> set to project-one, the runner currently finds the node_modules directory at the base of project-one and expects to be able to require eslint from it.

The situation looks to be similar if node_modules/eslint is at the base of the tree, as shown below. With <rootDir> set as before, eslint wouldn't be found because findUp discovers the first 'node_modules' from the <rootDir>, rather than the first 'node_modules/eslint'.

  Apps
    ...
    ├── packages
    |       ├── project-one
    |              ├── lib
    |              └── node_modules
    |              |       └── ...
    |              └── jest.config.js
    ├── node_modules
    |       ├── eslint
    |       └── ...

Hope this sheds some light on what I'm trying to do,

Thanks

[AndrewFinlay]

In consolidating my test tools in a separate project I'm trying to prevent a proliferation of eslint modules in each of the application projects. This is my preferred way of adding this functionality, however I can add separate eslint dependencies if need be.

In other words, is the project structure that I'd prefer to use likely to be supported by this module?