Skip StatementCache for eager loaded associations (Fixes #16761)

Eagerly loaded collection and singular associations are ignored by the StatementCache, which causes errors when the queries they generate reference columns that were not eagerly loaded.

This commit skips the creation of the StatementCache as a fix for these scenarios.

activerecord/lib/active_record/associations/collection_association.rb

@@ -407,7 +407,7 @@ def null_scope?
 
       private
       def get_records
-        return scope.to_a if reflection.scope_chain.any?(&:any?)
+        return scope.to_a if reflection.scope_chain.any?(&:any?) || scope.eager_loading?
 
         conn = klass.connection
         sc = reflection.association_scope_cache(conn, owner) do

activerecord/lib/active_record/associations/singular_association.rb

@@ -39,7 +39,7 @@ def create_scope
         end
 
         def get_records
-          return scope.limit(1).to_a if reflection.scope_chain.any?(&:any?)
+          return scope.limit(1).to_a if reflection.scope_chain.any?(&:any?) || scope.eager_loading?
 
           conn = klass.connection
           sc = reflection.association_scope_cache(conn, owner) do

activerecord/lib/active_record/core.rb

@@ -152,6 +152,7 @@ def find(*ids)
 
       def find_by(*args)
         return super if current_scope || !(Hash === args.first) || reflect_on_all_aggregations.any?
+        return super if default_scopes.any?
 
         hash = args.first
 

activerecord/test/cases/scoping/default_scoping_test.rb

 require 'cases/helper'
 require 'models/post'
+require 'models/comment'
 require 'models/developer'
 
 class DefaultScopingTest < ActiveRecord::TestCase
-  fixtures :developers, :posts
+  fixtures :developers, :posts, :comments
 
   def test_default_scope
     expected = Developer.all.merge!(:order => 'salary DESC').to_a.collect { |dev| dev.salary }
@@ -378,6 +379,24 @@ def test_default_scope_include_with_count
     assert_equal 1, DeveloperWithIncludes.where(:audit_logs => { :message => 'foo' }).count
   end
 
+  def test_default_scope_with_references_works_through_collection_association
+    post = PostWithCommentWithDefaultScopeReferencesAssociation.create!(title: "Hello World", body: "Here we go.")
+    comment = post.comment_with_default_scope_references_associations.create!(body: "Great post.", developer_id: Developer.first.id)
+    assert_equal comment, post.comment_with_default_scope_references_associations.to_a.first
+  end
+
+  def test_default_scope_with_references_works_through_association
+    post = PostWithCommentWithDefaultScopeReferencesAssociation.create!(title: "Hello World", body: "Here we go.")
+    comment = post.comment_with_default_scope_references_associations.create!(body: "Great post.", developer_id: Developer.first.id)
+    assert_equal comment, post.first_comment
+  end
+
+  def test_default_scope_with_references_works_with_find_by
+    post = PostWithCommentWithDefaultScopeReferencesAssociation.create!(title: "Hello World", body: "Here we go.")
+    comment = post.comment_with_default_scope_references_associations.create!(body: "Great post.", developer_id: Developer.first.id)
+    assert_equal comment, CommentWithDefaultScopeReferencesAssociation.find_by(id: comment.id)
+  end
+
   unless in_memory_db?
     def test_default_scope_is_threadsafe
       threads = []

activerecord/test/models/comment.rb

@@ -52,3 +52,8 @@ class CommentThatAutomaticallyAltersPostBody < Comment
     comment.post.update_attributes(body: "Automatically altered")
   end
 end
+
+class CommentWithDefaultScopeReferencesAssociation < Comment
+  default_scope ->{ includes(:developer).order('developers.name').references(:developer) }
+  belongs_to :developer
+end

activerecord/test/models/post.rb

@@ -218,3 +218,9 @@ class PostThatLoadsCommentsInAnAfterSaveHook < ActiveRecord::Base
     post.comments.load
   end
 end
+
+class PostWithCommentWithDefaultScopeReferencesAssociation < ActiveRecord::Base
+  self.table_name = 'posts'
+  has_many :comment_with_default_scope_references_associations, foreign_key: :post_id
+  has_one :first_comment, class_name: "CommentWithDefaultScopeReferencesAssociation", foreign_key: :post_id
+end