Very long build times (1min+), need speedups

[Maksims]

Currently, the engine takes a very long to build.
npm run build, on a good laptop (4 years old top gaming laptop), takes 1 minute and 16 seconds. And about 20 seconds for playcanvas.js file build.
Would be great if there would be a developer-focused build target (with watch variant), that would be built within few seconds (as fast as possible), that does not need many validations, etc, but needs for a quick test during the development process.

Previously builds were way faster than now.

[mvaligursky]

we have these target builds at the moment:

    case "es5":      targets = [target_release_es5,    target_extras]; break;
    case "es5min":   targets = [target_release_es5min, target_extras]; break;
    case "es6":      targets = [target_release_es6,    target_extras]; break;
    case "debug":    targets = [target_debug,          target_extras]; break;
    case "profiler": targets = [target_profiler,       target_extras]; break;

often I either use npm run build:es5 or npm run build:debug

[Maksims]

npm run build:es5 takes around 20 seconds, which is still very slow for testing during the development.

[mvaligursky]

On my laptop they're 14s each .. but agree if there's a way to speed it up, I'd like it.

[belohlavek]

What's the bottleneck? Have you considered esbuild?

[mvaligursky]

see a relevant ticket here #2103

[willeastcott]

@belohlavek The bottleneck (or main contributor to the build time) is Babel. If you disable Babel in the rollup.config.js, build time drops by about 65%.

[Maksims]

@belohlavek The bottleneck (or main contributor to the build time) is Babel. If you disable Babel in the rollup.config.js, build time drops by about 65%.

Probably worth investigating for a very fast build option, for development purposes, with a watcher, that allows the developer to iterate quickly on the engine.

[willeastcott]

This PR allows you to load the engine from source without having to build it: #3850

Maybe not useful for Editor users at the moment, but maybe interesting for engine devs or anybody running the engine in Node.

[willeastcott]

I have researched ways to get Babel to execute faster and it doesn't seem there is anything further we can do at this time. So since this isn't really a PlayCanvas issue, I'm going to close this. However, I'm still very interested in anyone's ideas to improve this. So if you think I've missed some practical thing we can be doing to achieve better build times, let me know and I can re-open the issue.

[yaustar]

Could we have a no babel build option for dev purposes? (Eg running against the Editor)

[willeastcott]

Yes, we could do that. But I just tried npm run watch:es5 and it takes 2.9 seconds to rebuild playcanvas.js instead of 13.8s for npm run build:es5.

As a result, I think we can just leave this closed.