Fix counter_cache create/concat with overlapping counter_cache_column

Fix when multiple `belongs_to` maps to the same counter_cache column.
In such situation `inverse_which_updates_counter_cache` may find the
wrong relation which leads into an invalid increment of the
counter_cache.

This is done by improving the inverse relation detection in 2 ways:
- by comparing `inverse.klass` with the current
  `active_record` (doesn't work for polymorphic)
- by relying on `inverse_of`

The above adjustments allows to correctly map the
`inverse_which_updates_counter_cache` for both non-polymorphic/polymorphic
relations.

Fixes rails#41250

activerecord/lib/active_record/reflection.rb

@@ -249,7 +249,9 @@ def check_validity_of_inverse!
       # Hence this method.
       def inverse_which_updates_counter_cache
         return @inverse_which_updates_counter_cache if defined?(@inverse_which_updates_counter_cache)
-        @inverse_which_updates_counter_cache = klass.reflect_on_all_associations(:belongs_to).find do |inverse|
+        inverse_candidates = inverse_of ? [inverse_of] : klass.reflect_on_all_associations(:belongs_to)
+        @inverse_which_updates_counter_cache = inverse_candidates.find do |inverse|
+          next false if inverse.klass_suppress_errors && inverse.klass_suppress_errors != active_record
           inverse.counter_cache_column == counter_cache_column
         end
       end
@@ -298,6 +300,11 @@ def actual_source_reflection # FIXME: this is a horrible name
           self
         end
 
+        def klass_suppress_errors
+          klass
+        rescue NameError, ArgumentError
+        end
+
       private
         def predicate_builder(table)
           PredicateBuilder.new(TableMetadata.new(klass, table))

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -41,6 +41,7 @@
 require "models/zine"
 require "models/interest"
 require "models/human"
+require "models/comment_overlapping_counter_cache"
 
 class HasManyAssociationsTestForReorderWithJoinDependency < ActiveRecord::TestCase
   fixtures :authors, :author_addresses, :posts, :comments
@@ -1361,6 +1362,23 @@ def test_counter_cache_updates_in_memory_after_update_with_inverse_of_disabled
     assert_equal 2, topic.reload.replies_count
   end
 
+  def test_counter_cache_updates_in_memory_after_create_with_overlapping_counter_cache_columns
+    user = UserCommentsCount.create!
+    post = PostCommentsCount.create!
+
+    assert_difference "user.comments_count", +1 do
+      assert_no_difference "post.comments_count" do
+        post.comments << CommentOverlappingCounterCache.create!(user_comments_count: user)
+      end
+    end
+
+    assert_difference "user.comments_count", +1 do
+      assert_no_difference "post.comments_count" do
+        user.comments << CommentOverlappingCounterCache.create!(post_comments_count: post)
+      end
+    end
+  end
+
   def test_counter_cache_updates_in_memory_after_update_with_inverse_of_enabled
     category = Category.create!(name: "Counter Cache")
 

activerecord/test/models/comment_overlapping_counter_cache.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class CommentOverlappingCounterCache < ActiveRecord::Base
+  belongs_to :user_comments_count, counter_cache: :comments_count
+  belongs_to :post_comments_count, class_name: "PostCommentsCount"
+  belongs_to :commentable, polymorphic: true, counter_cache: :comments_count
+end
+
+class UserCommentsCount < ActiveRecord::Base
+  has_many :comments, as: :commentable, class_name: "CommentOverlappingCounterCache"
+end
+
+class PostCommentsCount < ActiveRecord::Base
+  has_many :comments, class_name: "CommentOverlappingCounterCache"
+end

activerecord/test/schema/schema.rb

@@ -244,8 +244,14 @@
     t.integer :company
   end
 
+  create_table :comment_overlapping_counter_caches, force: true do |t|
+    t.integer :user_comments_count_id
+    t.integer :post_comments_count_id
+    t.references :commentable, polymorphic: true, index: false
+  end
+
   create_table :companies, force: true do |t|
-    t.string  :type
+    t.string :type
     t.references :firm, index: false
     t.string  :firm_name
     t.string  :name
@@ -843,6 +849,10 @@
     t.string :author_id
   end
 
+  create_table :post_comments_counts, force: true do |t|
+    t.integer :comments_count, default: 0
+  end
+
   create_table :serialized_posts, force: true do |t|
     t.integer :author_id
     t.string :title, null: false
@@ -1265,6 +1275,10 @@
     t.string :auth_token
   end
 
+  create_table :user_comments_counts, force: true do |t|
+    t.integer :comments_count, default: 0
+  end
+
   create_table :test_with_keyword_column_name, force: true do |t|
     t.string :desc
   end