Build default language with locale (adds preserveLocale flag)

[flakolefluk]

Currently when navigating to a page that does not have a locale, it will default the english one, this breaks the navigation (it doesn't really break it, but everything including links now changes locale to english)

This PR adds a preserveLocale flag that will run a second build of the files not included in the locale that exist in the "en" locale but using the current locale site.json.
Build time is considerably longer (en locale has almost 700 files, compared to others with 20 or less)
The result:

Open for discussion.

[ZYSzys]

It's awesome for me !👍

But is there anything we can do to make a bit more optimization ? That's even better :)

[flakolefluk]

As far as i know, there's no way to avoid building all the pages available in english (ignoring the ones already built for the current language) for every locale. I'm thinking of adding specific language builds, but i guess that is not part of this PR. Any advice?

[flakolefluk]

Looks like it solves #825

[ZYSzys]

/cc @fhemberger Can you please have a review on this, although I'm almost +1 for this(feature maybe).

[ZYSzys]

Since we also have preserveLocale in server.js, is it more reasonable to serve as node server.js --preserveLocale ? Or add one more script like build:deploy but for serve ?

[flakolefluk]

I think while developing is less needed to build all the files for every language. I think it's more relevant when deploying. But a second script in package.json might help.

Current options to serve with preserveLocale are:

npm start -- -- --preserveLocale
npm run serve -- --preserveLocale
node server.js --preserveLocale

I could add a script to run:

npm run serve:preserveLocale

[fhemberger]

If we decide to land this change, this would be a good opportunity to go over the process in general.

E.g. instead of building all languages for local testing/serving, setting DEFAULT_LOCALE=en by default and allow collaborators to overwrite that with an environment variable (e.g. DEFAULT_LOCALE=zh-cn npm run serve, when you're only working on the Chinese translation).

Only for deployment via CI all languages must be built.

This would save a lot of generation time for local development.

[fhemberger]

First of all: Thank you for your work! 👍

Only two little nits remaining:
a) See comment below
b) Could you add a short description of the build options (as in your comment above) to the README file?

FYI, I measured the time difference for a full build with and without --preserveLocale:

npm run build  12.83s user 1.62s system 118% cpu 12.215 total

rm -r build

npm run build -- --preserveLocale  113.75s user 9.43s system 125% cpu 1:38.04 total

As you can see, the latter took eight times as long. This probably isn't relevant during development, but this will have an impact on the build time during an actual release.

Therefore I'd love other members of @nodejs/website have a look as well.

[flakolefluk]

@fhemberger I added the requested changes to the readme section and when serving a different locale than english

[fhemberger]

@flakolefluk Thanks, LGTM now.
@ZYSzys If you are okay with it, we can merge it.

[ZYSzys]

Thank you!👍