Make --input-type=module work in general

[Pomax]

What is the problem this feature will solve?

Node cannot be used for one-time runs of ESM code in "no package.json" context or in CJS projects, or conversely in CJS mode in ESM projects, because --input-type is ignored when node is told to run a file rather than a string.

This includes not being able to run third party scripts in a project that has been written in "the other flavour" without transpiling, which makes very little sense when Node knows how to run both flavours of JS just fine, and just has no way to make it do so on a per-run basis.

What is the feature you are proposing to solve the problem?

Updating --input-type to apply to both strings and files, so that node --input-type=module onetimescript.js runs in ESM mode for that single run would be incredibly useful.

What alternatives have you considered?

There are no alternatives for telling Node which mode to run in on a per-run basis.

[vorbrodt]

Do you think this issue could be suitable for a new contributor? If so, I would like to be assigned to it and give it a try.

[aduh95]

Duplicate of https://github.com/nodejs/node/discussions/37857. The TL;DR I think can be summarise by:

• there's support for such a flag.
• it would probably involve loaders (actually it's already feasible with node --experimental-loader 'data:text/javascript,let entryPoint=true;export async function resolve(_,__,next){if(entryPoint){entryPoint=false;return {...(await next(...arguments)),format:"module"};}return next(...arguments)}' onetimescript.js).
• there's also arguments for not making this too much easier, as having well-defined rules on how to detect if a file should be treated as ESM or CJS, and having to create echo '{"type":"module"}' > package.json is also a workaround.

I'm going to close this to keep the discussion in the other thread, feel free to continue there.

[Pomax]

That thread has heavily derailed with massive scope creep including things like "what to do when there is no extension", "adding a completely different --package flag", etc. etc.

This is a very clear, well scoped request to extend --input-type to not just strings, but also files. The end. No scope creep, no "it'd be cool if we also", just a simple feature request to get a flag that already works, work better.

[al6x]

Node.JS is currently unable to execute standard JS.
Without creating package.json or nonsense .mjs extension.

[sbc100]

The link above seems to be completely missing (404): https://github.com/nodejs/node/discussions/37857

Can we re-open this issue perhaps? In emscripten it would be very useful for building command line JS applications that can be run via #! line without creating dummy package.json files alongside each of them. See emscripten-core/emscripten#24244