2 files changed, 53 insertions, 21 deletions

diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index 2daa48859a..6caf9b3251 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module Scoping
     module Default
@@ -5,11 +7,8 @@ module ActiveRecord
 
       included do
         # Stores the default scope for the class.
-        class_attribute :default_scopes, instance_writer: false, instance_predicate: false
-        class_attribute :default_scope_override, instance_writer: false, instance_predicate: false
-
-        self.default_scopes = []
-        self.default_scope_override = nil
+        class_attribute :default_scopes, instance_writer: false, instance_predicate: false, default: []
+        class_attribute :default_scope_override, instance_writer: false, instance_predicate: false, default: nil
       end
 
       module ClassMethods
@@ -32,7 +31,14 @@ module ActiveRecord
         #     Post.limit(10) # Fires "SELECT * FROM posts LIMIT 10"
         #   }
         def unscoped
-          block_given? ? relation.scoping { yield } : relation
+          block_given? ? _scoping(relation) { yield } : relation
+        end
+
+        def _scoping(relation) # :nodoc:
+          previous, self.current_scope = current_scope(true), relation
+          yield
+        ensure
+          self.current_scope = previous
         end
 
         # Are there attributes associated with this scope?
@@ -110,13 +116,17 @@ module ActiveRecord
 
             if default_scope_override
               # The user has defined their own default scope method, so call that
-              evaluate_default_scope { default_scope }
+              evaluate_default_scope do
+                if scope = default_scope
+                  (base_rel ||= relation).merge!(scope)
+                end
+              end
             elsif default_scopes.any?
               base_rel ||= relation
               evaluate_default_scope do
                 default_scopes.inject(base_rel) do |default_scope, scope|
                   scope = scope.respond_to?(:to_proc) ? scope : scope.method(:call)
-                  default_scope.merge(base_rel.instance_exec(&scope))
+                  default_scope.merge!(base_rel.instance_exec(&scope))
                 end
               end
             end
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index 27cdf8cb7e..573d97b819 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/array"
 require "active_support/core_ext/hash/except"
 require "active_support/core_ext/kernel/singleton_class"
@@ -22,20 +24,36 @@ module ActiveRecord
         # You can define a scope that applies to all finders using
         # {default_scope}[rdoc-ref:Scoping::Default::ClassMethods#default_scope].
         def all
-          if current_scope
-            current_scope.clone
+          scope = current_scope
+
+          if scope
+            if self == scope.klass
+              scope.clone
+            else
+              relation.merge!(scope)
+            end
           else
             default_scoped
           end
         end
 
-        def default_scoped # :nodoc:
-          scope = build_default_scope
+        def scope_for_association(scope = relation) # :nodoc:
+          if current_scope&.empty_scope?
+            scope
+          else
+            default_scoped(scope)
+          end
+        end
 
-          if scope
-            relation.spawn.merge!(scope)
+        def default_scoped(scope = relation) # :nodoc:
+          build_default_scope(scope) || scope
+        end
+
+        def default_extensions # :nodoc:
+          if scope = current_scope || build_default_scope
+            scope.extensions
           else
-            relation
+            []
           end
         end
 
@@ -151,22 +169,26 @@ module ActiveRecord
               "a class method with the same name."
           end
 
+          if method_defined_within?(name, Relation)
+            raise ArgumentError, "You tried to define a scope named \"#{name}\" " \
+              "on the model \"#{self.name}\", but ActiveRecord::Relation already defined " \
+              "an instance method with the same name."
+          end
+
           valid_scope_name?(name)
           extension = Module.new(&block) if block
 
           if body.respond_to?(:to_proc)
             singleton_class.send(:define_method, name) do |*args|
-              scope = all.scoping { instance_exec(*args, &body) }
+              scope = all._exec_scope(*args, &body)
               scope = scope.extending(extension) if extension
-
-              scope || all
+              scope
             end
           else
             singleton_class.send(:define_method, name) do |*args|
-              scope = all.scoping { body.call(*args) }
+              scope = body.call(*args) || all
               scope = scope.extending(extension) if extension
-
-              scope || all
+              scope
             end
           end
         end