webassembly/objpyproxy: Implement JS iterator protocol for Py iterables.

[dpgeorge]

This allows using JavaScript for..of on Python iterables.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.39%. Comparing base (50b43fe) to head (ac70b1e).

❗ Current head ac70b1e differs from pull request most recent head c056840. Consider uploading reports for the commit c056840 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #14435   +/-   ##
=======================================
  Coverage   98.39%   98.39%           
=======================================
  Files         161      161           
  Lines       21204    21204           
=======================================
  Hits        20864    20864           
  Misses        340      340           

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[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS

[WebReflection]

nit: this "screams" for a generator to me ... or better, that's usually how iterators are implemented in JS:

return function* () {
    while (true) {
        const value = Module._malloc(3 * 4);
        const valid = Module.ccall(
            "proxy_c_to_js_iternext",
            "number",
            ["number", "pointer"],
            [iter_ref, value],
        );
        if (valid) {
            yield proxy_convert_mp_to_js_obj_jsside_with_free(value);
        }
        else {
            Module._free(value);
            break;
        }
    }
};

Maybe it doesn't save much typing but at least it grants that the shape of the object is consistent, that is { done: true, value: void 0 } or { done: false, value: ... }.

[dpgeorge]

Thanks! I was hoping you would tell me the "right" way to do this 😄

Now updated as suggested.

[WebReflection]

virtually approved 👍

please remember to push incremental updates on npm for quicker feedback in case something ain't fully right (but to me this looks right) 🙏