Add tests for `TypeMap#fetch` and push up to `TypeMap`

It doesn't make sense for the subclass to implement this method, and not
have it on the parent. We can also DRY up the implementation of
`#lookup` to be defined in terms of fetch, which will give us a single
point of entry

2 files changed, 5 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/type/hash_lookup_type_map.rb b/activerecord/lib/active_record/type/hash_lookup_type_map.rb
index bf92680268..90a8c674cb 100644
--- a/activerecord/lib/active_record/type/hash_lookup_type_map.rb
+++ b/activerecord/lib/active_record/type/hash_lookup_type_map.rb
@@ -3,10 +3,6 @@ module ActiveRecord
     class HashLookupTypeMap < TypeMap # :nodoc:
       delegate :key?, to: :@mapping
 
-      def lookup(type, *args)
-        @mapping.fetch(type, proc { default_value }).call(type, *args)
-      end
-
       def fetch(type, *args, &block)
         @mapping.fetch(type, block).call(type, *args)
       end
diff --git a/activerecord/lib/active_record/type/type_map.rb b/activerecord/lib/active_record/type/type_map.rb
index 88c5f9c497..13d4943861 100644
--- a/activerecord/lib/active_record/type/type_map.rb
+++ b/activerecord/lib/active_record/type/type_map.rb
@@ -6,6 +6,10 @@ module ActiveRecord
       end
 
       def lookup(lookup_key, *args)
+        fetch(lookup_key, *args) { default_value }
+      end
+
+      def fetch(lookup_key, *args)
         matching_pair = @mapping.reverse_each.detect do |key, _|
           key === lookup_key
         end
@@ -13,7 +17,7 @@ module ActiveRecord
         if matching_pair
           matching_pair.last.call(lookup_key, *args)
         else
-          default_value
+          yield lookup_key, *args
         end
       end