cli: rename --loader to --experimental-loader

[reasonablytall]

Renames the --loader cli argument to --experimental-loader. This is
to clearly indicate the esm loader feature as experimental even after
esm is no longer experimental.

Also minorly alters the --experimental-loader docs to say that the
passed loader can be an esm module.

An alternative to this PR is to leave things unchanged and continue to use --experimental-modules to allow the use of --loader, even after ECMAScript modules are unflagged. This would reduce the number of different argument schemes a hypothetical script that wraps node would need to try, as discussed here: nodejs/modules#351 (comment)

Refs: nodejs/modules#351 (comment)

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[addaleax]

Is the intention to go back to using --loader once ESM is no longer experimental? If so – and maybe also if not – I’d recommend providing --loader as an (for-now-)undocumented alias via AddAlias().

[guybedford]

@addaleax the intention is to unflag modules while leaving loader as experimental for the time being, unflagging only after the development work to bring loaders to stable. Whether this could happen for 12 or only in 13 is another question too, and one we were hoping to get some feedback from on the releases group side.

[addaleax]

@guybedford Okay, then replace “once ESM is no longer experimental” with “once ESM loaders are no longer experimental” :)

[reasonablytall]

Using --experimental-loader prints an experimental warning message, so having --loader as an undocumented alias seems reasonable to me. I'll make the change.

The check is failing because I use cli as a subsystem. I'll change that to src since node_options.cc is the most affected.

[addaleax]

The check is failing because I use cli as a subsystem. I'll change that to src since node_options.cc is the most affected.

I would ignore that, tbh. cli or esm are both better choices than src, imo.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25752/

[cjihrig]

I think doc/node.1 needs to be updated as well.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25778/

[Trott]

Landed in 15fb02a