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

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In our case the exception was triggered by an outdated tzdata package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 078421bacba178eac6a8e607b16f3f4511c5d72f `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.

4 files changed, 35 insertions, 1 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 82c985fae2..aa7e206bb2 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Fix bug where `ActiveSupport::Timezone.all` would fail when tzinfo data for
+    any timezone defined in `ActiveSupport::MAPPING` is missing.
+
+    *Dominik Sander*
+
 *   Fix bug where `ActiveSupport::Cache` will massively inflate the storage
     size when compression is enabled (which is true by default). This patch
     does not attempt to repair existing data: please manually flush the cache
diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index 9dfaddb825..5f709c5fd9 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -279,7 +279,8 @@ module ActiveSupport
 
         def zones_map
           @zones_map ||= MAPPING.each_with_object({}) do |(name, _), zones|
-            zones[name] = self[name]
+            timezone = self[name]
+            zones[name] = timezone if timezone
           end
         end
     end
diff --git a/activesupport/test/time_zone_test.rb b/activesupport/test/time_zone_test.rb
index 63ca22efb5..120afa61f2 100644
--- a/activesupport/test/time_zone_test.rb
+++ b/activesupport/test/time_zone_test.rb
@@ -725,6 +725,21 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_not_includes all_zones, galapagos
   end
 
+  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
+
   def test_index
     assert_nil ActiveSupport::TimeZone["bogus"]
     assert_instance_of ActiveSupport::TimeZone, ActiveSupport::TimeZone["Central Time (US & Canada)"]
diff --git a/activesupport/test/time_zone_test_helpers.rb b/activesupport/test/time_zone_test_helpers.rb
index 051703a781..85ed727c9b 100644
--- a/activesupport/test/time_zone_test_helpers.rb
+++ b/activesupport/test/time_zone_test_helpers.rb
@@ -23,4 +23,17 @@ module TimeZoneTestHelpers
   ensure
     ActiveSupport.to_time_preserves_timezone = old_preserve_tz
   end
+
+  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
 end