Find more stable way of including bs-platform/lib/js/*

[seenaburns]

Problem

Isolate's startup time on Windows became abysmally slow (~30-60s) after adding React and Reason as dependencies.

Investigating, I found the app had high disk activity, and appeared to be creating a new directory under ~/AppData/Local/Temp/... that would contain the unpacked asar, with just 300mb of bs-platform. The exe was only 60mb, so I suspect on EVERY startup it was unpacking, compiling the bs-platform tooling, and then deleting it after the app closes, but I would need to do more investigation.

Unfortunately bs-platform does not expose the runtime libraries as a separate package, so the only way to include these dependencies (for example bs-platform/lib/js/array.js) is to include all of bs-platform

Workaround

505d15932c82053ea58d7e09adf146e82b0f56f7 includes a janky addition to build.sh which copies out bs-platform/lib/js/*.js and reason-react into local modules, includes them in the electron-builder build and replaces all references to the bs-platform module with local modules.

# From build.sh
replace_deps() {
    sed -i '' "s|require(\"$1|require(\"$2|g" $3;
}

if [ ! -d build/bs-stdlib ]; then
    mkdir -p build/bs-stdlib/lib/js
    cp -r node_modules/bs-platform/lib/js/* build/bs-stdlib/lib/js/
fi

if [ ! -d build/reason-react ]; then
    mkdir -p build/reason-react/src/
    cp -r node_modules/reason-react/src/*.js build/reason-react/src/
    for f in $(find build/reason-react -iname '*.js'); do
        replace_deps "bs-platform" "../../../build/bs-stdlib" $f
    done
fi

for f in $(find src -iname '*.bs.js'); do
    replace_deps "bs-platform" "../build/bs-stdlib" $f
    replace_deps "reason-react" "../build/reason-react" $f
done

Better solution

Ideally BuckleScript/bucklescript/pull/2171 or BuckleScript/bucklescript/issues/2127 will separate bs-platform's Javascript stdlib into a separate package. This would be preferable because the *.bs.js files and any other libraries (e.g. reason-react) reference bs-platform. Changing the compilation of these files seems more stable than hacking at the require references afterwards.

Short of that, maybe there's a more stable way of doing this in the build. Maybe replacing require references is what webpack is for, and could make vendoring these libraries easier.