Fix relation.create to avoid leaking scope to initialization block and callbacks

`relation.create` populates scope attributes to new record by `scoping`,
it is necessary to assign the scope attributes to the record and to find
STI subclass from the scope attributes.

But the effect of `scoping` is class global, it was caused undesired
behavior that pollute all class level querying methods in initialization
block and callbacks (`after_initialize`, `before_validation`,
`before_save`, etc), which are user provided code.

To avoid the leaking scope issue, restore the original current scope
before initialization block and callbacks are invoked.

Fixes #9894.
Fixes #17577.
Closes #31526.

activerecord/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Fix `relation.create` to avoid leaking scope to initialization block and callbacks.
+
+    Fixes #9894, #17577.
+
+    *Ryuta Kamizono*
+
 *   Chaining named scope is no longer leaking to class level querying methods.
 
     Fixes #14003.

activerecord/lib/active_record/relation.rb

@@ -67,6 +67,11 @@ def bind_attribute(name, value) # :nodoc:
     #   user = users.new { |user| user.name = 'Oscar' }
     #   user.name # => Oscar
     def new(attributes = nil, &block)
+      current_scope = klass.current_scope(true)
+      block = -> record do
+        klass.current_scope = current_scope
+        yield record if block_given?
+      end
       scoping { klass.new(attributes, &block) }
     end
 
@@ -92,7 +97,11 @@ def new(attributes = nil, &block)
     #   users.create(name: nil) # validation on name
     #   # => #<User id: nil, name: nil, ...>
     def create(attributes = nil, &block)
-      scoping { klass.create(attributes, &block) }
+      if attributes.is_a?(Array)
+        attributes.collect { |attr| create(attr, &block) }
+      else
+        new(attributes, &block).tap(&:save)
+      end
     end
 
     # Similar to #create, but calls
@@ -102,7 +111,11 @@ def create(attributes = nil, &block)
     # Expects arguments in the same format as
     # {ActiveRecord::Base.create!}[rdoc-ref:Persistence::ClassMethods#create!].
     def create!(attributes = nil, &block)
-      scoping { klass.create!(attributes, &block) }
+      if attributes.is_a?(Array)
+        attributes.collect { |attr| create!(attr, &block) }
+      else
+        new(attributes, &block).tap(&:save!)
+      end
     end
 
     def first_or_create(attributes = nil, &block) # :nodoc:

activerecord/test/cases/base_test.rb

@@ -1535,7 +1535,7 @@ def test_protected_environments_are_stored_as_an_array_of_string
     Bird.create!(name: "Bluejay")
 
     ActiveRecord::Base.connection.while_preventing_writes do
-      assert_queries(2) { Bird.where(name: "Bluejay").explain }
+      assert_nothing_raised { Bird.where(name: "Bluejay").explain }
     end
   end
 

activerecord/test/cases/relations_test.rb

@@ -1167,7 +1167,12 @@ def test_first_or_create_with_no_parameters
   end
 
   def test_first_or_create_with_block
-    parrot = Bird.where(color: "green").first_or_create { |bird| bird.name = "parrot" }
+    canary = Bird.create!(color: "yellow", name: "canary")
+    parrot = Bird.where(color: "green").first_or_create do |bird|
+      bird.name = "parrot"
+      assert_equal canary, Bird.find_by!(name: "canary")
+    end
+    assert_equal 1, parrot.total_count
     assert_kind_of Bird, parrot
     assert_predicate parrot, :persisted?
     assert_equal "green", parrot.color
@@ -1209,7 +1214,12 @@ def test_first_or_create_bang_with_no_parameters
   end
 
   def test_first_or_create_bang_with_valid_block
-    parrot = Bird.where(color: "green").first_or_create! { |bird| bird.name = "parrot" }
+    canary = Bird.create!(color: "yellow", name: "canary")
+    parrot = Bird.where(color: "green").first_or_create! do |bird|
+      bird.name = "parrot"
+      assert_equal canary, Bird.find_by!(name: "canary")
+    end
+    assert_equal 1, parrot.total_count
     assert_kind_of Bird, parrot
     assert_predicate parrot, :persisted?
     assert_equal "green", parrot.color
@@ -1259,7 +1269,12 @@ def test_first_or_initialize_with_no_parameters
   end
 
   def test_first_or_initialize_with_block
-    parrot = Bird.where(color: "green").first_or_initialize { |bird| bird.name = "parrot" }
+    canary = Bird.create!(color: "yellow", name: "canary")
+    parrot = Bird.where(color: "green").first_or_initialize do |bird|
+      bird.name = "parrot"
+      assert_equal canary, Bird.find_by!(name: "canary")
+    end
+    assert_equal 1, parrot.total_count
     assert_kind_of Bird, parrot
     assert_not_predicate parrot, :persisted?
     assert_predicate parrot, :valid?

activerecord/test/models/bird.rb

@@ -16,4 +16,9 @@ class Bird < ActiveRecord::Base
   def cancel_save_callback_method
     throw(:abort)
   end
+
+  attr_accessor :total_count
+  after_initialize do
+    self.total_count = Bird.count
+  end
 end