store tzinfo time zones

app/cells/settings/time_zone_setting_cell.rb

@@ -48,8 +48,28 @@ module Settings
 
     ##
     # Returns time zone (label, value) tuples to be used for a select field.
+    # As we only store tzinfo compatible data we only provide options, for which the
+    # values can later on be retrieved unambiguously. This is not always the case
+    # for values in ActiveSupport::TimeZone since multiple AS zones map to single tzinfo zones.
     def time_zone_entries
-      time_zones.map { |tz| [tz.to_s, tz.name] }
+      time_zones
+        .group_by { |tz| tz.tzinfo.name }
+        .values
+        .map do |zones|
+        tz = namesake_time_zone(zones)
+
+        [tz.to_s, tz.tzinfo.canonical_identifier]
+      end
+    end
+
+    # If there are multiple AS::TimeZones for a single TZInfo::Timezone, we
+    # one return the one that is the namesake.
+    def namesake_time_zone(time_zones)
+      if time_zones.length == 1
+        time_zones.first
+      else
+        time_zones.detect { |tz| tz.tzinfo.name.include?(tz.name.gsub(' ', '_')) }
+      end
     end
   end
 end

app/contracts/user_preferences/base_contract.rb

@@ -54,7 +54,10 @@ module UserPreferences
     protected
 
     def time_zone_correctness
-      errors.add(:time_zone, :inclusion) if model.time_zone.present? && model.canonical_time_zone.nil?
+      if model.time_zone.present? &&
+         ActiveSupport::TimeZone[model.time_zone]&.tzinfo&.canonical_identifier != model.time_zone
+        errors.add(:time_zone, :inclusion)
+      end
     end
 
     ##

spec/contracts/user_preferences/update_contract_spec.rb

@@ -50,8 +50,9 @@ describe UserPreferences::UpdateContract do
         enabled: true,
         times: %w[08:00:00+00:00 12:00:00+00:00]
       },
-      time_zone: 'Brasilia',
-      warn_on_leaving_unsaved: true
+      time_zone: 'America/Sao_Paulo',
+      warn_on_leaving_unsaved: true,
+      workdays: [1, 2, 4, 6]
     }
   end
   let(:contract) { described_class.new(user_preference, current_user) }
@@ -237,36 +238,34 @@ describe UserPreferences::UpdateContract do
     it_behaves_like 'contract is invalid', time_zone: :inclusion
   end
 
-  describe 'workdays' do
-    context 'with valid entries' do
-      let(:settings) do
-        {
-          workdays: [1, 2, 4, 6]
-        }
-      end
-
-      it_behaves_like 'contract is valid'
+  context 'with a non tzinfo time_zone' do
+    let(:settings) do
+      {
+        time_zone: 'Brasilia'
+      }
     end
 
-    context 'with duplicate entries' do
-      let(:settings) do
-        {
-          workdays: [1, 1]
-        }
-      end
+    it_behaves_like 'contract is invalid', time_zone: :inclusion
+  end
 
-      it_behaves_like 'contract is invalid', workdays: :no_duplicates
+  context 'with duplicate workday entries' do
+    let(:settings) do
+      {
+        workdays: [1, 1]
+      }
     end
 
-    context 'with non-iso entries' do
-      let(:settings) do
-        {
-          workdays: [nil, 'foo', :bar, 21345, 2.0]
-        }
-      end
+    it_behaves_like 'contract is invalid', workdays: :no_duplicates
+  end
 
-      it_behaves_like 'contract is invalid', workdays: %i[invalid type_mismatch_nested
-                                                          type_mismatch_nested type_mismatch_nested]
+  context 'with non-iso workday entries' do
+    let(:settings) do
+      {
+        workdays: [nil, 'foo', :bar, 21345, 2.0]
+      }
     end
+
+    it_behaves_like 'contract is invalid', workdays: %i[invalid type_mismatch_nested
+                                                        type_mismatch_nested type_mismatch_nested]
   end
 end