Investigate deprecation of --compilers

[boneskull]

--compilers may be useless with later versions of Node.js, and commonly --require is sufficient instead. Example:

--compilers js:babel-register

Is better written as

--require babel-register

I don't know if this

--compilers coffee:coffee-script/register

Is equivalent to this:

--require coffee-script

If so, it's probably only true for some versions of Node.js and/or coffee-script.

If you use a different extension with Babel--say .es6--I think you would need --compilers? How does this work with TypeScript?

Regardless, --compilers js:some_module may always be better written with --require if that extension is .js. Something similar is noted in the docs.

[ScottFreeCode]

I just looked at the code, and it doesn't seem like Mocha is actually doing anything to associate the particular compiler with the particular extension, just requireing the compiler and adding the extension to the list of test/watch extensions, which I believe is used somewhere in the file lookup logic if you haven't specified a glob. In other words, if I understand correct, --compilers <ext>:<compiler> <folder> should be equivalent to --require <compiler> "<folder>/*.{js,<ext>}" and --compilers <ext>:<compiler> --recursive <folder> should be equivalent to --require <compiler> "<folder>/**/*.{js,<ext>}". With --watch I'm not sure if there's an equivalent (since I'm not aware of any way to specify which files/folders to watch), but considering we would really like to get Mocha to where we can stop having to handle such stuff in --watch too...

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[ScottFreeCode]

I just double-checked control of watch's extensions, and there is indeed another commandline argument for that. --compilers <ext>:<compiler> --watch <folder> should be equivalent to --require <compiler> --watch-extensions <ext> --watch "<folder>/*.{js,<ext>}" and --compilers <ext>:<compiler> --watch --recursive <folder> should be equivalent to --require <compiler> --watch-extensions <ext> --watch "<folder>/**/*.{js,<ext>}"

As far as I can see, we should go ahead and document that --compilers is just a shortcut for --require and adding extensions to your test files pattern (and to --watch-extensions if using --watch), and then we can get rid of --compilers in a semver major version.

[fesebuv]

@ScottFreeCode is this issue resolved? Does it require further action?

[ScottFreeCode]

As far as I recall, we figured out how to entirely replace --compilers with --require, --watch-extensions and globbing, but I don't remember whether we verified that the needed glob pattern can be quoted with the same syntax on both Unixy and non-Unixy OSes (:cough-windows-cough:), and I'm fairly sure we didn't decide whether to deprecate it or merely document what it's shorthand for. I will double-check that the relevant glob syntax is useable portably and if so ping the team for a decision on deprecation.

[fesebuv]

@ScottFreeCode excellent!

[boneskull]

Regarding .mjs, see @std/esm, which is pretty awesome.

[ScottFreeCode]

Created #3005 to prove with testing that one can glob multiple extensions, works in both OSes.

The glob has changed since my prior investigation, due to upgrading the Glob package; it is now @(first_extension|second_extension) instead of {first_extension,second_extension}.