Configure Rails application i18n configuration in railtie

[rochlefebvre]

What are you trying to accomplish?

Part of https://github.com/Shopify/address/issues/2796

In the context of a Rails application, call Worldwide::Config.configure_i18n with the application's i18n config instance instead of the statically-available I18n.config object. Avoid configuring the same i18n config instance more than once.

What approach did you choose and why?

Configure Rails application's existing i18n state

Invoke Worldwide::Config.configure_i18n in the gem railtie's initializer block, passing in the application's config.i18n instance.

Only configure an i18n config instance once

Maintain a class instance variable in Worldwide::Config that remembers each i18n config object that was successfully configured by the configure_i18n method. Subsequent calls to configure_i18n that operate on the same i18n instance will return early.

Calling Worldwide::Config.configure_i18n with the same i18n config instance is not technically idempotent, as the method also accepts an optional additional_components parameter. This example shows the limitations of my implementation:

some_config = I18n::Config.new

Worldwide::Config.configure_i18n(i18n_config: some_config) # updates some_config
Worldwide::Config.configure_i18n(
  i18n_config: some_config,
  additional_components: [:some_component],
) # ignores some_component directive, returns early

What should reviewers focus on?

I chose to use a set an array that remembers previously-seen i18n configs rather than try to manage their state in the context of repeated invocations to configure_i18n. I did not come up with a cheap and clean way to maintain a sane set of updates to i18n configurations, so I went with this simple approach.

If someone wants to run configure_i18n on an i18n config instance after the first invocation, they can manipulate the cache with Worldwide::Config.previously_configured_i18ns.clear and take on the responsibility of editing the i18n config instance accordingly.

Testing

Railtie testing

In a Rails app, I introduced a railtie that configured the shared i18n configs available_locales, ensuring that this railtie's initializer ran before Worldwide's own railie:

class Railtie < ::Rails::Railtie
  initializer "some-gem", before: Worldwide::Rails::Railtie::SETUP do |app|
    app.config.i18n.available_locales = [:en, :fr]
  end
end

The railties initialized in the desired order.

Avoid configuring i18n config more than once

In a large app that has both direct and transitive dependencies on Worldwide, with several configuration classes that wind up calling Worldwide::Config.configure_i18n on a shared i18n config instance, only the first call to configure_i18n actually updated the i18n config instance.

Checklist

• I have added a CHANGELOG entry for this change (or determined that it isn't needed)

[rochlefebvre]

I originally used a set instead of an array, then learned that sets have surprising behaviour for inclusion by object identity:

(byebug) Worldwide::Config.previously_configured_i18ns.class.name
"Set"
(byebug) Worldwide::Config.previously_configured_i18ns.first === i18n_config
true
(byebug) Worldwide::Config.previously_configured_i18ns.include?(i18n_config)
false
(byebug) Worldwide::Config.previously_configured_i18ns.first.object_id
64480
(byebug) i18n_config.object_id
64480

I believe we're supposed to call Set#compare_by_identity, but there is no guaranteed support on all ruby flavours.

An array is just fine.

Copilot reviewed 6 out of 7 changed files in this pull request and generated no suggestions.

Files not reviewed (1)

• CHANGELOG.md: Evaluated as low risk