Faster / parellel i18n AOT builds

[itslenny]

Bug Report or Feature Request (mark with an x)

- [ ] bug report -> please search issues before submitting
- [ X ] feature request

Versions.

@angular/cli: 1.1.3
node: 6.10.1
os: darwin x64
@angular/animations: 4.2.4
@angular/common: 4.2.4
@angular/compiler: 4.2.4
@angular/compiler-cli: 4.2.4
@angular/core: 4.2.4
@angular/flex-layout: 2.0.0-beta.8
@angular/forms: 4.2.4
@angular/http: 4.2.4
@angular/material: 2.0.0-beta.7
@angular/platform-browser: 4.2.4
@angular/platform-browser-dynamic: 4.2.4
@angular/platform-server: 4.2.4
@angular/router: 4.2.4
@angular/cli: 1.1.3

Desired functionality.

I'm working on a fairly large app that uses AOT and i18n localization, and we need to translate into 60+ languages. Currently the only option is to run ng build for each language one at a time. For my app this takes 5 hours to complete running them in series. My short-term mitigation is to run ng build in parallel which will helps, but I think we can do better.

My thought is adding something like ng build -prod --i18n-config i18n-config.json

Then, in the config file you could list all the languages you want and the destination directories for each and ng-cli would run them in parallel. Additionally, it feels like it could do the AOT build once and hold the AST in memory then generate each language without having to re-do the entire AOT build for every language. I haven't fully researched this, and I know it'd add a lot of complexity, but for enterprise scale global apps this is absolutely needed to have reasonable build times.

[chcaru]

I agree, this will enable the real world use case of having a large team with a large app that has continuous delivery and many languages. What is available right now simply doesn't scale.

[filipesilva]

Yeah I can't really argue that 5h is a lot of time to build your app for all languages. I suppose at a low level, the apps array could be leveraged to that effect and used with a ng build --all or something. Wouldn't be much different from just using a shell script like you do currently though.

Saving part of the compilation from before sounds like a better idea, but much more complex. It would also require some explicit support from ngc itself.

[intellix]

In the hopes of improving what we have, this is how we're currently compiling our site for each language. Let me know if you have anything better for parallelism :)

{
  "scripts": {
    "build": "ng build --target=production -e ${NG_ENV:-prod} --aot",
    "build:i18n": "npm run build -- --output-path=dist/${LANG:-en} --bh /${LANG:-en}/ --i18n-file=src/locale/messages.${LANG:-en}.xlf --locale=${LANG:-en}",
    "heroku-postbuild": "for lang in en de sv; do LANG=$lang npm run build:i18n; if [ $? -ne 0 ]; then echo ERROR; exit 666; fi; done",
    "xi18n": "ng xi18n --i18n-format=xlf --out-file=locale/messages.xlf",
  }
}

Upon building in Heroku, it'll run the heroku-postbuild task which will start compiling languages one by one. If one of them fails then the whole build will fail. We originally tried to do things in parallel but an error would get swallowed up and report that the build was successful when it wasn't

[ocombe]

We have the same problem at google and it is now reaching the limit of our build systems as well. We are working on improvements for v5, stay tuned!

[intellix]

@ocombe just wanted to checkup on the timeline for the above stuff as v5 landed now :)
I'm guessing this is now a CLI thing since we have AOT watch mode and baking in the languages can be done much quicker?

[ocombe]

It will not be parallel builds. We are working on something called "runtime i18n" right now, we'll bundle all translations in the same bundle and apply the translation at runtime (without needing a compiler, so this is still AOT-safe). This means only one build even if you have 100 languages.
It should land in 5.1 or 5.2 (depending if we find any blocker that requires more work).

[SURENDARREDDY]

@ocombe , Anyway we are doing this for all the languages, Why can't we add for all environments.
I mean build only one for all languages and all environments once.
any chance?

[aldo-roman]

@ocombe I think "runtime i18n" approach would allow the user to change the app language without losing app state. Currently, AFAIK, to change a language you have to reload the complete app again. You also need different bundles, which means more downloads.

Any clue on how this is going? Sounds really great.

[chcaru]

@aldo-roman I think this is being tracked as part of this issue now:
angular/angular#16477