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.

6 files changed, 34 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index 065a2cff01..1836ff0910 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -407,7 +407,7 @@ module ActiveRecord
 
       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
diff --git a/activerecord/lib/active_record/associations/singular_association.rb b/activerecord/lib/active_record/associations/singular_association.rb
index f2e3a4e40f..b9326b9683 100644
--- a/activerecord/lib/active_record/associations/singular_association.rb
+++ b/activerecord/lib/active_record/associations/singular_association.rb
@@ -39,7 +39,7 @@ module ActiveRecord
         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
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 82b9c79533..2e9c9e3197 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -152,6 +152,7 @@ module ActiveRecord
 
       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
 
diff --git a/activerecord/test/cases/scoping/default_scoping_test.rb b/activerecord/test/cases/scoping/default_scoping_test.rb
index 9a4d8c6740..a5c4404175 100644
--- a/activerecord/test/cases/scoping/default_scoping_test.rb
+++ b/activerecord/test/cases/scoping/default_scoping_test.rb
@@ -1,9 +1,10 @@
 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 @@ class DefaultScopingTest < ActiveRecord::TestCase
     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 = []
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index 7a88299d08..b38b17e90e 100644
--- a/activerecord/test/models/comment.rb
+++ b/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
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 56a31011da..256b720c9a 100644
--- a/activerecord/test/models/post.rb
+++ b/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