From 5c6d3653830465176ed9d37ec210d55d6ab62852 Mon Sep 17 00:00:00 2001
From: Matthew Draper <matthew@trebex.net>
Date: Mon, 11 Jan 2016 16:33:16 +1030
Subject: [PATCH] Skip the STI condition when evaluating a default scope

Given a default_scope on a parent of the current class, where that
parent is not the base class, the parent's STI condition would become
attached to the evaluated default scope, and then override the child's
own STI condition.

Instead, we can treat the STI condition as though it is a default scope,
and skip it in this situation: the scope will be merged into the base
relation, which already contains the correct STI condition.

Fixes #22426.
---
 activerecord/lib/active_record/core.rb             |  2 +-
 activerecord/lib/active_record/scoping/default.rb  |  4 ++--
 .../test/cases/scoping/default_scoping_test.rb     | 14 ++++++++++++++
 activerecord/test/models/post.rb                   |  7 +++++++
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 1250f8a3c3..475a298467 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -275,7 +275,7 @@ def cached_find_by_statement(key, &block) # :nodoc:
       def relation # :nodoc:
         relation = Relation.create(self, arel_table, predicate_builder)
 
-        if finder_needs_type_condition?
+        if finder_needs_type_condition? && !ignore_default_scope?
           relation.where(type_condition).create_with(inheritance_column.to_sym => sti_name)
         else
           relation
diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index cdcb73382f..8baf3b8044 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -122,11 +122,11 @@ def build_default_scope(base_rel = nil) # :nodoc:
         end
 
         def ignore_default_scope? # :nodoc:
-          ScopeRegistry.value_for(:ignore_default_scope, self)
+          ScopeRegistry.value_for(:ignore_default_scope, base_class)
         end
 
         def ignore_default_scope=(ignore) # :nodoc:
-          ScopeRegistry.set_value_for(:ignore_default_scope, self, ignore)
+          ScopeRegistry.set_value_for(:ignore_default_scope, base_class, ignore)
         end
 
         # The ignore_default_scope flag is used to prevent an infinite recursion
diff --git a/activerecord/test/cases/scoping/default_scoping_test.rb b/activerecord/test/cases/scoping/default_scoping_test.rb
index 86316ab476..ad5ca70f36 100644
--- a/activerecord/test/cases/scoping/default_scoping_test.rb
+++ b/activerecord/test/cases/scoping/default_scoping_test.rb
@@ -459,4 +459,18 @@ def test_with_abstract_class_where_clause_should_not_be_duplicated
     scope = Bus.all
     assert_equal scope.where_clause.ast.children.length, 1
   end
+
+  def test_sti_conditions_are_not_carried_in_default_scope
+    ConditionalStiPost.create! body: ''
+    SubConditionalStiPost.create! body: ''
+    SubConditionalStiPost.create! title: 'Hello world', body: ''
+
+    assert_equal 2, ConditionalStiPost.count
+    assert_equal 2, ConditionalStiPost.all.to_a.size
+    assert_equal 3, ConditionalStiPost.unscope(where: :title).to_a.size
+
+    assert_equal 1, SubConditionalStiPost.count
+    assert_equal 1, SubConditionalStiPost.all.to_a.size
+    assert_equal 2, SubConditionalStiPost.unscope(where: :title).to_a.size
+  end
 end
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 23cebe2602..bf3079a1df 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -263,3 +263,10 @@ class PostWithCommentWithDefaultScopeReferencesAssociation < ActiveRecord::Base
 class SerializedPost < ActiveRecord::Base
   serialize :title
 end
+
+class ConditionalStiPost < Post
+  default_scope { where(title: 'Untitled') }
+end
+
+class SubConditionalStiPost < ConditionalStiPost
+end
-- 
GitLab