"compilers" does not compile fork scripts

[maxclaus]

Running a project that depend on some features not available in the latest Node js yet such as async await I use --compilers js:babel-register on mocha to compile my code during the tests. This works really well in most cases. But this does not work if I have a fork process which also use async.

If I run babel-node over the main script it will by default compile the fork scripts as well.
But running mocha with --compilers js:babel-register it does not happen. I was expecting it would work the same way babel-node does.

Here is the a project to help reproduce the problem: https://github.com/maxcnunes/problem-fork-with-babel-node

[boneskull]

(--compilers isn't needed here; you can use --require babel-register; see docs)

process.execPath must be babel-node for any forked process to run babel-node. --require and --compilers have no interaction with this.

three potential workarounds off the top of my head:

• run Mocha with babel-node /path/to/mocha (the mocha executable forks the _mocha executable; it should retain process.execPath, but if it doesn't, babel-node _mocha would work instead)
• in your test or test fixture, manually set process.execPath to /path/to/babel-node (though this may have unintended consequences)
• manually set the execPath option when forking to /path/to/babel-node

related: #2517

[maxclaus]

Thanks @boneskull. From all your suggestions the only one I had not tried before was babel-node /path/to/mocha. Which by the way is the only one works 😄

So running babel-node node_modules/mocha/bin/_mocha test.js applies by default the compiler to the child process.

PS: Once you run the mocha with babel-node there is no need to pass --require or --compilers.

[boneskull]

as I understand babel-node is especially slow versus other methods. have you found this to be true?