Allow for dynamic import() to be used in eslint config file

The version of ESLint you are using.

ESLint-v7.8.1

The problem you want to solve.

Currently, while eslint understands the meaning of the .cjs extension, it is unable to load a config file that uses dinamic import() statements. It fails with an error:

TypeError [ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING]: A dynamic import callback was not specified.

This is caused by the dependency v8-compile-cache which patches the node internal Module.prototype._compile method in an insufficient fashion.

The purpouse of solving this is easier handeling of eslint configs for esm-users until config-file-simplification arrives (RFC). The Roadmap estimated the implementation to arrive in 5 months (6 months when the statement was made).

Your take on the correct solution to problem.

As the problem is caused by a dependency, there is no straight forward solution. I’ll file an issue in in the project after i’m done here. issue filed

NOTE: While debugging the issue, I found some things that are potential road-blocks for esm support (like the dependency import-fresh, which dispite the name is for loading cjs). I’ll be doing some more exploring and will post a proper report (propaby in the RFC repo) once i have some spare time.

Are you willing to submit a pull request to implement this change?

Potentially. I’ll check what exactly would need to have to change in v8-compile-cache and possibly make a PR there to solve the problem at the root. Besides that, it depends on what I find while examining the things mentioned in the note.

NOTE: A quick-fix is setting the env-variable DISABLE_V8_COMPILE_CACHE

[trusktr]

The assignment to module.exports happens later in the queue:

it doesn’t seem possible to use import() in actual config files anyway.

Here’s how to import ES Modules in a synchronous way:

const deasync = require('deasync'); // powerful magic

const promiseSync = deasync((promise, cb) => {
  promise.then((result) => cb(null, result)).catch((error) => cb(error));
});

const importSync = (name) => promiseSync(import(name));

// Look, no await needed here!
const something = importSync('./something.js').default;

module.exports = {
  ...something,
  // ...
}

See deasync

Running with DISABLE_V8_COMPILE_CACHE=1 eslint . works great!

[mdjermanovic]

Awesome, thanks for sharing this!