From cec55aafb9191b0bd357679453170c60196479fa Mon Sep 17 00:00:00 2001
From: Dinah Shi <dinahshi@github.com>
Date: Thu, 24 Jun 2021 11:54:40 -0400
Subject: [PATCH] Convert strict_loading_mode from class attr to ivar

Strict loading mode `:n_plus_one_only` is only
supported on single records, not associations or
models. Using an ivar instead of class_attribute
ensures that this cannot be set globally. This
fixes a bug where setting `strict_loading_mode`
caused errors to be silent when
`strict_loading_by_default` is true.

Fixes #42576

Co-Authored-By: John Hawthorn <john@hawthorn.email>
---
 .../active_record/associations/association.rb |  2 +-
 activerecord/lib/active_record/core.rb        |  5 ++-
 .../test/cases/strict_loading_test.rb         | 45 -------------------
 3 files changed, 4 insertions(+), 48 deletions(-)

diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index 20cdc69fb9..2b88f53df0 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -240,7 +240,7 @@ module ActiveRecord
             if owner.strict_loading_n_plus_one_only? && reflection.macro == :has_many
               record.strict_loading!
             else
-              record.strict_loading_mode = owner.strict_loading_mode
+              record.strict_loading!(false, mode: owner.strict_loading_mode)
             end
           end
         end
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 6c30cc4b79..eea6210e41 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -68,7 +68,6 @@ module ActiveRecord
       class_attribute :belongs_to_required_by_default, instance_accessor: false
 
       class_attribute :strict_loading_by_default, instance_accessor: false, default: false
-      class_attribute :strict_loading_mode, instance_accessor: true, default: :all
 
       class_attribute :has_many_inversing, instance_accessor: false, default: false
 
@@ -677,6 +676,8 @@ module ActiveRecord
       @strict_loading = value
     end
 
+    attr_reader :strict_loading_mode
+
     # Returns +true+ if the record uses strict_loading with +:n_plus_one_only+ mode enabled.
     def strict_loading_n_plus_one_only?
       @strict_loading_mode == :n_plus_one_only
@@ -768,7 +769,7 @@ module ActiveRecord
 
         @primary_key         = klass.primary_key
         @strict_loading      = klass.strict_loading_by_default
-        @strict_loading_mode = klass.strict_loading_mode
+        @strict_loading_mode = :all
 
         klass.define_attribute_methods
       end
diff --git a/activerecord/test/cases/strict_loading_test.rb b/activerecord/test/cases/strict_loading_test.rb
index 200d3f4dd1..052cca9fc7 100644
--- a/activerecord/test/cases/strict_loading_test.rb
+++ b/activerecord/test/cases/strict_loading_test.rb
@@ -77,51 +77,6 @@ class StrictLoadingTest < ActiveRecord::TestCase
     end
   end
 
-  def test_strict_loading_n_plus_one_only_mode_by_default
-    with_strict_loading_by_default(Developer) do
-      previous_strict_loading_mode = Developer.strict_loading_mode
-      Developer.strict_loading_mode = :n_plus_one_only
-
-      developer = Developer.first
-      ship = Ship.first
-      ShipPart.create!(name: "Stern", ship: ship)
-      firm = Firm.create!(name: "NASA")
-      project = Project.create!(name: "Apollo", firm: firm)
-
-      ship.update_column(:developer_id, developer.id)
-      developer.projects << project
-      developer.reload
-
-      assert_predicate developer, :strict_loading?
-
-      # Does not raise when loading a has_many association (:projects)
-      assert_nothing_raised do
-        developer.projects.to_a
-      end
-
-      # strict_loading is enabled for has_many associations
-      assert developer.projects.all?(&:strict_loading?)
-      assert_raises ActiveRecord::StrictLoadingViolationError do
-        developer.projects.last.firm
-      end
-
-      # Does not raise when a belongs_to association (:ship) loads its
-      # has_many association (:parts)
-      assert_nothing_raised do
-        developer.ship.parts.to_a
-      end
-
-      # strict_loading is enabled for has_many through a belongs_to
-      assert_not developer.ship.strict_loading?
-      assert developer.ship.parts.all?(&:strict_loading?)
-      assert_raises ActiveRecord::StrictLoadingViolationError do
-        developer.ship.parts.first.trinkets.to_a
-      end
-    ensure
-      Developer.strict_loading_mode = previous_strict_loading_mode
-    end
-  end
-
   def test_strict_loading
     Developer.all.each { |d| assert_not d.strict_loading? }
     Developer.strict_loading.each { |d| assert d.strict_loading? }