I have updated a few tests and verified that the whole test suite succeeded locally (npm test), and also verified that the build worked (npm run build)

Thanks for the contribution @josundt. @Sayan751 and I have had already the Intl RelativeTime feature on our plate. Safari, and specifically Safari iOS was one of the major holdbacks to do the port.

With your approach we'd definitely get the best of it going forward for unsupported browsers but it comes with a large overhead for typically only a small amount of locales used.

The best approach perhaps would be that the plugin ships your script and users can generate their own translations and register them via the plugin options. What do you think @Sayan751?

PS, while Intl translations are regarded standard perhaps some users still prefer the current ones. So the recommended approach would allow both options

EDIT:
ok hold on I think I've misunderstood and you're actually just fixing the existing ones instead of adding all available locales. Nevertheless it might be worth thinking about the alternative approach proposed in order to reduce the plugins size.

Additionally may I ask you to exclude the files from dist folders from this PR, as these will be generated during the release.

In my opinion, translations that comes with i18n should not differ from the defined language standards even if certain contributors prefer some different flavor. Personal preferences should probably not override national standards. Pluralization rules cannot be fully represented through i18n translations - f.ex. in Arabic I noticed that the numeric is not included when the integer the count is 1, but also not when it is 2! Certain locales have different rules for 1, 2 and many (and some even more). Still, getting as close as possible with the national standards will probably make the potential future transition to Intl.RelativeTimeFormat easier.

The challenge with the current solution as mentioned is that as you increase the number of supported locales you also increase the size of this plugin.

In the Aurelia applications developed by my organization, we use Aurelia with webpack, we do not use bundling of translations; we simply copy (and compact) the json source translation files to the webpack output folder (using CopyWebpackPlugin), and we have made our own fetch-based i18next loader that dynamically loads translations over HTTP when the user changes user locale (appending a per-build unique queryString value for cache-boosting).

For us it would have been a sufficient solution if the aurelia-i18n npm package included standard i18n per-locale JSON translation files for the relative time translations, so that we could include the languages we support in the webpack build process.

As an alternative, there could have been a small cli tool, a webpack plugin or similar included with the package to generate these files during build. The package would need full-icu as a dependency/peerDependency (a.k.a. not devDependency) for this to work.

To test my added translation generator, please review the build/translation-generator/index.ts file and maybe pull the PR and run npm run build:translations once. I think the code I wrote can be easily reused for both scenarios described above.

I have updated the PR, removing the dist folder and with a few improvements to the generator script.

In Au2 we are already using the Intl API. Personally, I find it pretty cool. It means less things for me as a developer to ship with the application. We can gladly make the switch in Au1 as well.

Regarding browser support, devs can always use polyfill like this: https://www.npmjs.com/package/relative-time-format to get the translation.

import RelativeTimeFormat from 'relative-time-format';
import * as deRt from 'relative-time-format/locale/de.json';
import * as enRt from 'relative-time-format/locale/en.json';
RelativeTimeFormat.addLocale(enRt['default']);
RelativeTimeFormat.addLocale(deRt['default']);
Intl['RelativeTimeFormat'] = Intl['RelativeTimeFormat'] || RelativeTimeFormat;

Generating the translation using the Intl API, and shipping that with aurelia-i18n package on the other hand seems bit counter intuitive.

Thanks for the update @Sayan751 totally forgot that it already got introduced in v2.

I wont be able to do the backport in the next two weeks as I'm starting tomorrow at my new job. If you can wait all good otherwise you maybe want to give it a shot by yourself. You can find the newly introduced rt method from the i18n service here which then would be used in the ValueConverter instead of the custom RtService. So yep it would result in a minor breaking change with a major bump but it shouldn't be too dramatic since I don't expect lots of users consuming the coded approach to create RTs

I think I will probably not be able to contribute to any "backport", but looking forward to the Intl based version in Aurelia 2.
I have personally already written an Intl based service+value converter+binding behavior solution for our applicatoin suite, my plan was actually to use aurelia-i18n as a fallback solution (for Safari etc).

@Sayan751 I was actually not aware that a polyfill existed for Intl.RelativeTimeFormat, I thought this feature would be hard to polyfill. But from the looks of your code sample, it seems to be to possible to both bundle locale json files or to dynamically load them over HTTP. The latter should be a good solution in our case.

I have tested 3rd party libraries earlier that used "raw" locale pluralization rules data to generate language phrases of different kinds. Some of those libraries were dynamically generating and evaluating code, and this did not work with our Content-Security-Policy (no script-src: 'unsafe-eval'). I hope the RelativeTimeFormat polyfill does not rely on dynamic code generation and evaluation.

I think I will cancel this PR, but I would still like to create a new PR with updated translations, at least for the Scandinavian languages. The current translations are bad, and the Norwegian (bokmål) language code is even wrong.

Please let me know if you want me to update only the Scandinavian languages or all the currently supported languages.

Sounds good, yeah we'd be glad for the updates languages meanwhile. While at it let's do it for all currently supported.

@zewa666 I have now updated the translations in "src/defaultTranslations/relative.time.ts" as requested using my generator script. (I realized that I can actually also generate the "now" translation with Intl, so those are also updated for all the currently supported locales.)

I think I will ask for this PR to be merged after all instead of creating a new one. Hope that's OK. This PR includes, in addition to the udpated translations; 3 additional ts files under the build/translation-generator folder + an added npm run-script command (in package.json) - I guess it does not hurt to include this - you decide if you want to use it or not. If someone asks for a translation to another language you will be able to generate it by adding the new locale to the "supported-locales.ts" file and run the npm command.

Remarks:
My tool (npm run build:translations) could now actually rewrite the whole src/defaultTranslations/relative.time.ts file, the single drawback is that the node full-icu does not include the zh-TW locale, so you would loose that single translation. For this reason I decided that the command will still just writes to src/defaultTranslations/relative.time.generated.ts - right next to the original. (The path can be changed in the npm script in package.json if you decide to loose zh-TW for the sake of full automation).
(PS! You may notice that the zh-CH is also removed, since my generator removes "sub-locales" (e.g. zh-CH) when every translation is identical to the main locale (e.g. zh). This should not cause any issues).

I had to update a few tests and ran all tests + build successfully on my machine, not sure why the circleci reports test/ci failures.

Hoping you will accept this PR, and I'm also hoping that a minor release can be scheduled ASAP, since an upcoming product feature in my company relies on the improved translations.

@zewa666 Do you have time to review and hopefully accept this soon?

Hey, super sorry for the delay but I'm burried under work currently. Can I ask you to keep the PR open but create one merely with the unit test fixes and the updated translations. I simply won't have time for a proper review and could get this new one merged quicker along with a patch release.

Thanks again and sorry for the troubles, hope things will get better in near future.

@zewa666 I have now created a separate PR with only the updated translations and tests: #323.

Feel free to review the translation-generator in this PR at a later time. It is just a separate standalone npm run-script command that you may run on demand when needed; I have not altered any other build or test scripts..

Fixed the misplaced zh-TW in relative time tranlations - same fix as in #323