Consider to add .js extenstion to main entry point (bin/mocha) for better ES modules compatibility

[evg656e]

Is your feature request related to a problem or a nice-to-have?? Please describe.

Since extensionless files in ESM context was dropped in latest node versions, there is a problem problem using the Mocha with new esm-loaders like ts-node esm-loader, e.g.:

node --loader ts-node/esm.mjs node_modules/mocha/bin/mocha --extension ts

causes error now:

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension "" for node_modules/mocha/bin/mocha

Describe the solution you'd like
Rename bin/mocha to bin/mocha.js and add new bin/mocha which simply requires new bin/mocha.js (e.g. require('./mocha.js');) for backward compatibility.

Describe alternatives you've considered
n/a

Additional context
nodejs/node#31415
nodejs/node#33223 (comment)

[cspotcode]

FYI I posted on nodejs/node#33223 that I actually believe this is a bug on node's side. mocha declares itself to be a commonjs module, not ESM, so node should not be attempting to load it as ESM.

[boneskull]

bin/mocha is not the main entry point; it's an executable. You should not be requiring or importing it.

See #4298 for further discussion.

[cspotcode]

@boneskull To clarify, the use-case is invoking the executable while passing --loader to node, not to require or import the main entry point. Makes more sense when the example uses _mocha instead of mocha; not sure if _mocha has been deprecated.

# Fails due to the bug I filed in node's issue tracker
node --loader ts-node/esm node_modules/mocha/bin/_mocha --extension ts

# Allowing mocha to pass the --loader flag to node (this works)
mocha --loader=ts-node/esm --extension ts

# Omitting the equal sign breaks, even though node supports this.  Worth noting.
mocha --loader ts-node/esm --extension ts

[boneskull]

Ahh, yes, thanks.

The recommended way would be to use mocha instead of node; it will spawn a node process, running lib/cli/cli.js with the non-Mocha flags passed to node.

_mocha is just a stub for lib/cli/cli.js, but it’s still there for backwards-compat.

we should open an issue to look into the = thing.