central issue for "default extensions"

[ljharb]

This issue encompasses anything that deals with "what the default extensions are/should be".

• opts.extensions should include '.json' #19 points out that .json is not included in the defaults.
• resolve does not preserve require.extensions list and assumes only ['.js'] #137 points out that require.extensions is not used as the defaults
• Tape does not pass require.extensions to resolve tape-testing/tape#395 is related, but can be addressed with changes in tape, unrelated to whatever resolve does.
• (related but addressed: Node's require.resolve options #150, Absolute paths don't take opts.extensions into account #127, cannot resolve paths with extentions .min.js #90, Missing documentation on how the extensions option is used. #134)

There's some PRs out that are hoping to change the defaults:

• Update to use default require.extensions #138 dynamically reads require.extensions on every call
• Update default extensions to match node #145 replaces the default of .js with a hardcoded list of the default require.extensions value

I'm opening this so I can close the other issues, and so any further discussion can happen here.

Please try to read all of the previous discussions before commenting.

[snuggs]

@ljharb well done! I'm subscribed and have my eyes peeled. Seems like as I predicted last year there will be more eyeballs looking in the require.extensions direction.

This is a great synopsis but even myself remember you had made a couple suggestions. I wonder what they are currently (especially with the new .mjs extension add we've been working on with IETF. This way I can see where I can help and take some concerns off your plate.

Thoughts?

[ljharb]

As it relates to .mjs, resolve will absolutely add it to the default extension list the instant node ships it unflagged - but not before (that will also be when it's present in require.extensions in node).

[snuggs]

@ljharb sounds like a plan! Any ref we can use to stick in the description / comment to watchdog?

Seems like you know better than me. I've merely been judging off PTSD of the community and in the classrooms. :-|

FWIW I'm totally against .mjs and believe it creates some unnecessary social fractures within the ecosystem but that's just my opinion not the community at large's.

[ljharb]

A file extension is strictly necessary, since Module and Script have distinct (and ambiguous) parsing goals, and a file extension is the proper and sole way to disambiguate textual parsing goals - so this result was inevitable once the choice of two parse goals was made in TC39 back in 2013 or so.