Fix exception in AS::Timezone.all when any tzinfo data is missing

[dsander]

Before this change missing timezone data for any of the time zones defined in ActiveSupport::Timezone::MAPPING caused a comparison of NilClass with ActiveSupport::TimeZone failed exception.

Attempting to get a timezone by passing a number/duration to [] or calling all directly will try to sort sort the values of zones_map. Those values are initialized by the return value of create(zonename) which returns nil if TZInfo is unable to find the timezone information.

In our case the exception was triggered by an outdated tzdata package which did not include information for the "recently" added time zones.

Before 078421b zones_map only returned the information that have been loaded into @lazy_zone_map which ignored time zones for which the data could not be loaded, this change restores the previous behaviour.

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[rafaelfranca]

How would this happen in real world? All zones defined in that constant we know exists.

[dsander]

They do exist if the tzdata system package is current, but when it is not TZInfo does not know anything about them and raises an exception itself. Before 078421b AS::Timezone.all just omitted those timezones.

[pixeltrix]

Replace this method with this:

def with_tz_mappings(mappings)
  old_mappings = ActiveSupport::TimeZone::MAPPING.dup
  ActiveSupport::TimeZone.clear
  ActiveSupport::TimeZone::MAPPING.clear
  ActiveSupport::TimeZone::MAPPING.merge!(mappings)

  yield
ensure
  ActiveSupport::TimeZone.clear
  ActiveSupport::TimeZone::MAPPING.clear
  ActiveSupport::TimeZone::MAPPING.merge!(old_mappings)
end

and use as explained above.

[pixeltrix]

While creating a subclass works as a way of reproducing the error it doesn't really reflect real-life usage so I'd prefer a test that more accurately reflects the error which we can do by changing the mappings for this test using the helper method in the comment below. With that you can then change the test to this:

def test_all_not_raises_exception_with_mizzing_tzinfo_data
  mappings = {
    "Puerto Rico" => "America/Unknown",
    "Pittsburgh"  => "America/New_York"
  }

  with_tz_mappings(mappings) do
    assert_nil ActiveSupport::TimeZone["Puerto Rico"]
    assert_nil ActiveSupport::TimeZone[-9]
    assert_nothing_raised do
      ActiveSupport::TimeZone.all
    end
  end
end

[dsander]

Thanks, I wasn't particular happy with creating the subclass and now realize that I created the test from the wrong "perspective".

[pixeltrix]

I think the change is 👍 we just need to change the tests as I've outlined, thanks.

[dsander]

@pixeltrix Thanks for the feedback, should I squash the commits into one?

[rafaelfranca]

should I squash the commits into one?

Yes

[pixeltrix]

@dsander thanks! 👍