Pass Module to callback functions

[kleisauke]

This ensures that users can still invoke runtime elements within the
preRun function that are exported on Module (for e.g. ENV or FS)
when compiling with -s MODULARIZE=1.

Example usage:

var options = {
    preRun: [function (module) {
        module.ENV.hello = 'world';
        module.FS.createPreloadedFile('/', 'foo', 'bar', true, false);
    }]
};
Module(options).then(function (module) {

});

Note: this example requires that the code is compiled with

-s "EXTRA_EXPORTED_RUNTIME_METHODS=['FS', 'ENV']"

Resolves #9827.

[welcome]

Thank you for submitting a pull request! If this is your first PR, make sure to add yourself to AUTHORS.

[kripken]

Good idea, thanks @kleisauke !

I wonder if this might be best to just do in all modes and not just modularize. By doing it all the time people can easily flip between the modes without problems (otherwise, modularize => non modularize could break). This does increase code size a tiny bit, but it's very very little, and seems worth it to me. What do you think?

[kleisauke]

Yes, that makes sense. Done with 0bd7cc9, also added some tests for this in 9ea25da. I guess that I don't have to make the same change in preamble_minimal.js?

emscripten/src/preamble_minimal.js

Line 228 in c755d1f

callback();

Since it seems that with -s MINIMAL_RUNTIME=1 only the __ATEXIT__ callbacks are called.

[kripken]

Yes, in the minimal runtime these callbacks aren't supported yet, so nothing to do there.

[kripken]

Perfect, thanks @kleisauke !

I think it would also be good to document this on the site. Perhaps on https://emscripten.org/docs/api_reference/module.html or https://emscripten.org/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html? (both are under site/ in this repo)

But let's land this first, that can be a followup. Would be great if you can open a PR for that!

[kripken]

(Oh, also we should update the Changelog later.)