Correct errors in counter cache updating

The cache name should be converted to a string when given, not compared
as a symbol. This edge case is already adequately covered by our tests,
but was masked by another issue where we were incorrectly updating the
counter cache twice. When paired with a bug where we didn't update the
counter cache because we couldn't find a match with the name, this made
it look like everything was working fine.

Fixes #10865.

activerecord/CHANGELOG.md

+*   Fixed several edge cases which could result in a counter cache updating
+    twice or not updating at all for `has_many` and `has_many :through`.
+
+    Fixes #10865.
+
+    *Sean Griffin*
+
 *   Foreign keys added by migrations were given random, generated names. This
     meant a different `structure.sql` would be generated every time a developer
     ran migrations on their machine.

activerecord/lib/active_record/associations/has_many_association.rb

@@ -85,7 +85,11 @@ def has_cached_counter?(reflection = reflection())
         end
 
         def cached_counter_attribute_name(reflection = reflection())
-          options[:counter_cache] || "#{reflection.name}_count"
+          if reflection.options[:counter_cache]
+            reflection.options[:counter_cache].to_s
+          else
+            "#{reflection.name}_count"
+          end
         end
 
         def update_counter(difference, reflection = reflection())

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -160,9 +160,9 @@ def delete_records(records, method)
 
           if through_reflection.collection? && update_through_counter?(method)
             update_counter(-count, through_reflection)
+          else
+            update_counter(-count)
           end
-
-          update_counter(-count)
         end
 
         def through_records_for(record)