Fix locale setting

[mateusdeap]

Summary

Better late than never.

This PR aims to make the locale setting work in threaded server environments.

It adds back the @locale class variable to Faker::Config and adds a new thread unsafe method that sets that variable. That way we can still set the locale on a per thread basis with Faker::Config.locale or we can set it in a global manner using Faker::Config.locale!

As a final remark, not really sure this does what we want it to do, but tests still pass.

Also would like to give a shout out to @nateberkopec, @hlascelles, @stefannibrasil and @thdaraujo for all the help and patience.

P.S.: I might need some help with writing tests. I kind of know how to write the tests, just not sure in what file to add it.

Fixes Issue #2563

[stefannibrasil]

I've been running behind on reviews, will check out this tomorrow. In the meantime, could you take a look at the rubocop failure? Thank you 🚀

[stefannibrasil]

@mateusdeap thank you for your contribution so far! Sorry for the late response.

I think that having a configuration option which sets the default locale in a non-threadsafe way by having a:

Faker.configure do |config|
  config.locale = :en
  (...)
end

can be worth introducing on faker. It seems like that's the easiest way to set that default locale initially. @thdaraujo thoughts? It would be a breaking change, and we can create a new release for it, no worries.

Something I had in mind is to include this test from this branch, as it shows the desired behaviour of setting the locale globally with per-thread locales. It's just a start but it gives us a start 💭

If I add this test when trying the branch locally, I have some failing specs, though. Updated: see comment below.

About your question of where to place the tests, there is the faker test file. Another option is add the tests to the test_locale file. But I am okay with creating a new test file just for testing threads. What do you think?

[stefannibrasil]

Sorry, I first missed the ! in Faker::Config.locale!.

These are now passing:

  def test_setting_default_locale
    # if locale is not set, fallback is :en
    assert_equal :en, Faker::Config.locale

    # locale can be updated initially
    # and it becomes the default value
    # for new threads
    Faker::Config.locale!(:pt)

    assert_equal :pt, Faker::Config.locale

    t1 = Thread.new do
      # child thread has initial locale equal to
      # latest locale set on main thread
      # instead of the fallback value
      assert_equal :pt, Faker::Config.locale

      # child thread can set its own locale
      Faker::Config.locale = :es
      assert_equal :es, Faker::Config.locale
    end

    t1.join

    # child thread won't change locale of other threads
    assert_equal :pt, Faker::Config.locale

    t2 = Thread.new do
      # initial default locale is copied over to new thread
      assert_equal :pt, Faker::Config.locale

      Faker::Config.locale = :it
      assert_equal :it, Faker::Config.locale
    end

    t2.join

    assert_equal :pt, Faker::Config.locale

    # setting this to reset the default locale for all tests
    Faker::Config.locale!(nil)
    assert_equal :en, Faker::Config.locale
  end

  def test_setting_default_locale_on_child_thread
    # if locale is not set, fallback is :en
    assert_equal :en, Faker::Config.locale

    # locale can be updated initially
    # and it becomes the default value
    # for new threads
    Faker::Config.locale!(:pt)

    assert_equal :pt, Faker::Config.locale

    t1 = Thread.new do
      # child thread has initial locale equal to
      # latest locale set on main thread
      # instead of the fallback value
      assert_equal :pt, Faker::Config.locale

      # child thread can set the default locale
      Faker::Config.locale!(:es)
      assert_equal :es, Faker::Config.locale
    end

    t1.join

    # all threads now will have the same default
    assert_equal :es, Faker::Config.locale

    t2 = Thread.new do
      # initial default locale is copied over to new thread
      assert_equal :es, Faker::Config.locale

      Faker::Config.locale = :it
      assert_equal :it, Faker::Config.locale
    end

    t2.join

    assert_equal :es, Faker::Config.locale

    # setting this to reset the default locale for all tests
    Faker::Config.locale!(nil)
    assert_equal :en, Faker::Config.locale
  end

We'll need to update the docs as well to guide folks on how to use this as well. I confess I'm not super familiar with this, so hopefully @thdaraujo can chime in to give some ideas on the tests and docs 🙏

[thdaraujo]

thanks for working on this and being so helpful, @mateusdeap!

For testing, we can just add a new file called faker/test/test_default_locale.rb and base it off of the specs that @stefannibrasil shared. That would be good enough.

See my comment about changing to default_locale and let me know what you think.

[stefannibrasil]

Merging this and I will add the test and update the README in a follow up PR. Thank you @mateusdeap for your contribution!