Benchmark:

localized components:

Warming up --------------------------------------
component: 13.862k i/100ms
partial: 2.296k i/100ms
Calculating -------------------------------------
component: 139.812k (± 0.9%) i/s - 1.400M in 10.014746s
partial: 22.876k (± 3.2%) i/s - 229.600k in 10.047667s

main branch:

Warming up --------------------------------------
component: 13.007k i/100ms
partial: 2.440k i/100ms
Calculating -------------------------------------
component: 129.883k (± 1.9%) i/s - 1.301M in 10.018044s
partial: 24.145k (± 3.6%) i/s - 241.560k in 10.021579s

I'm doing some tests in a dummy app, with the following configuration:

I18n.available_locales = [:en, :es, :fr]
I18n.default_locale = :en

I'm adding a FooComponent with 3 partials:

app/components/foo_component.en.html.erb
# no partial for `es`
app/components/foo_component.fr.html.erb
app/components/foo_component.html.erb

• If I set I18n.locale = :en in my request, I get the foo_component.html.erb ➡️ I would expect foo_component.en.html.erb
• If I set I18n.locale = :es in my request, I get the foo_component.html.erb ✔️
• If I set I18n.locale = :fr in my request, I get the foo_component.fr.html.erb ✔️
• If I set no locale in my request, I get the foo_component.html.erb ➡️ I would expect the I18n.default_locale to be used, so foo_component.en.html.erb

Now If I'm removing this partial and restart the server :

app/components/foo_component.en.html.erb
app/components/foo_component.fr.html.erb
- app/components/foo_component.html.erb

• If I set I18n.locale = :en in my request, I get an error undefined local variable or method 'call' for #<FooComponent:0x00007f9720c56610>
• If I set I18n.locale = :es in my request, I get an error undefined local variable or method 'call' for #<FooComponent:0x00007f9720c56610>
• If I set I18n.locale = :fr in my request, I get the foo_component.fr.html.erb ✔️
• If I set no locale in my request, I get an error undefined local variable or method 'call' for #<FooComponent:0x00007f9720c56610>

I guess it should work without a "default" partial, what do you think?

EDIT: here is the standard behavior with localized views in Rails:

app/views/pages/show.en.html.erb
# no view for `es`
app/views/pages/show.fr.html.erb
app/views/pages/show.html.erb

• If I set I18n.locale = :en in my request, I get the show.en.html.erb
• If I set I18n.locale = :es in my request, I get the show.en.html.erb
• If I set I18n.locale = :fr in my request, I get the show.fr.html.erb
• If I set no locale in my request, I get the show.en.html.erb
• Actually, I never get the show.html.erb and I can remove it without getting errors

Thanks for reviewing it @Spone

I think every case is expected as I used the I18n.default_locale as the default, without locale information in the filename. I mean, if you set I18n.default_locale = :en there's no need to have all your files with '.en'.... 🤔

There's a (test) for this.

If I set I18n.locale = :es in my request, I get an error undefined local variable or method 'call' for #FooComponent:0x00007f9720c56610

This happened because there's no foo_component.es.html.erb. You think we should to fallback to the foo_component.html.erb ?

If I set no locale in my request, I get an error undefined local variable or method 'call' for #FooComponent:0x00007f9720c56610

Also expected, as the file foo_component.html.erb was deleted.

If I set no locale in my request, I get the show.en.html.erb
Actually, I never get the show.html.erb and I can remove it without getting errors

Without locale, but with I18n.default_locale = :en right?

This happened because there's no foo_component.es.html.erb. You think we should to fallback to the foo_component.html.erb ?

In this case, Rails localized views fall back to the default locale (so foo_component.en.html.erb in this case).

Also expected, as the file foo_component.html.erb was deleted.

Yes but in this case Rails localized views fall back to the default locale as well.

Without locale, but with I18n.default_locale = :en right?

Yes. Actually you can also remove it from the config since :en is the default value.

To sum up, I think the fall back behavior should be the same as Rails standard behavior with localized views, as described in the EDIT of my previous comment. What do you think?

Thanks @Spone and @jonspalmer for the comments. I'll have a look into it carefully.

@lfalcao is there any news on this PR?