1 files changed, 152 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/scoping.rb b/activerecord/lib/active_record/scoping.rb
new file mode 100644
index 0000000000..a8f5e96190
--- /dev/null
+++ b/activerecord/lib/active_record/scoping.rb
@@ -0,0 +1,152 @@
+require 'active_support/concern'
+
+module ActiveRecord
+  module Scoping
+    extend ActiveSupport::Concern
+
+    included do
+      include Default
+      include Named
+    end
+
+    module ClassMethods
+      # with_scope lets you apply options to inner block incrementally. It takes a hash and the keys must be
+      # <tt>:find</tt> or <tt>:create</tt>. <tt>:find</tt> parameter is <tt>Relation</tt> while
+      # <tt>:create</tt> parameters are an attributes hash.
+      #
+      #   class Article < ActiveRecord::Base
+      #     def self.create_with_scope
+      #       with_scope(:find => where(:blog_id => 1), :create => { :blog_id => 1 }) do
+      #         find(1) # => SELECT * from articles WHERE blog_id = 1 AND id = 1
+      #         a = create(1)
+      #         a.blog_id # => 1
+      #       end
+      #     end
+      #   end
+      #
+      # In nested scopings, all previous parameters are overwritten by the innermost rule, with the exception of
+      # <tt>where</tt>, <tt>includes</tt>, and <tt>joins</tt> operations in <tt>Relation</tt>, which are merged.
+      #
+      # <tt>joins</tt> operations are uniqued so multiple scopes can join in the same table without table aliasing
+      # problems. If you need to join multiple tables, but still want one of the tables to be uniqued, use the
+      # array of strings format for your joins.
+      #
+      #   class Article < ActiveRecord::Base
+      #     def self.find_with_scope
+      #       with_scope(:find => where(:blog_id => 1).limit(1), :create => { :blog_id => 1 }) do
+      #         with_scope(:find => limit(10)) do
+      #           all # => SELECT * from articles WHERE blog_id = 1 LIMIT 10
+      #         end
+      #         with_scope(:find => where(:author_id => 3)) do
+      #           all # => SELECT * from articles WHERE blog_id = 1 AND author_id = 3 LIMIT 1
+      #         end
+      #       end
+      #     end
+      #   end
+      #
+      # You can ignore any previous scopings by using the <tt>with_exclusive_scope</tt> method.
+      #
+      #   class Article < ActiveRecord::Base
+      #     def self.find_with_exclusive_scope
+      #       with_scope(:find => where(:blog_id => 1).limit(1)) do
+      #         with_exclusive_scope(:find => limit(10)) do
+      #           all # => SELECT * from articles LIMIT 10
+      #         end
+      #       end
+      #     end
+      #   end
+      #
+      # *Note*: the +:find+ scope also has effect on update and deletion methods, like +update_all+ and +delete_all+.
+      def with_scope(scope = {}, action = :merge, &block)
+        # If another Active Record class has been passed in, get its current scope
+        scope = scope.current_scope if !scope.is_a?(Relation) && scope.respond_to?(:current_scope)
+
+        previous_scope = self.current_scope
+
+        if scope.is_a?(Hash)
+          # Dup first and second level of hash (method and params).
+          scope = scope.dup
+          scope.each do |method, params|
+            scope[method] = params.dup unless params == true
+          end
+
+          scope.assert_valid_keys([ :find, :create ])
+          relation = construct_finder_arel(scope[:find] || {})
+          relation.default_scoped = true unless action == :overwrite
+
+          if previous_scope && previous_scope.create_with_value && scope[:create]
+            scope_for_create = if action == :merge
+              previous_scope.create_with_value.merge(scope[:create])
+            else
+              scope[:create]
+            end
+
+            relation = relation.create_with(scope_for_create)
+          else
+            scope_for_create = scope[:create]
+            scope_for_create ||= previous_scope.create_with_value if previous_scope
+            relation = relation.create_with(scope_for_create) if scope_for_create
+          end
+
+          scope = relation
+        end
+
+        scope = previous_scope.merge(scope) if previous_scope && action == :merge
+
+        self.current_scope = scope
+        begin
+          yield
+        ensure
+          self.current_scope = previous_scope
+        end
+      end
+
+      protected
+
+      # Works like with_scope, but discards any nested properties.
+      def with_exclusive_scope(method_scoping = {}, &block)
+        if method_scoping.values.any? { |e| e.is_a?(ActiveRecord::Relation) }
+          raise ArgumentError, <<-MSG
+  New finder API can not be used with_exclusive_scope. You can either call unscoped to get an anonymous scope not bound to the default_scope:
+
+  User.unscoped.where(:active => true)
+
+  Or call unscoped with a block:
+
+  User.unscoped do
+  User.where(:active => true).all
+  end
+
+  MSG
+        end
+        with_scope(method_scoping, :overwrite, &block)
+      end
+
+      def current_scope #:nodoc:
+        Thread.current["#{self}_current_scope"]
+      end
+
+      def current_scope=(scope) #:nodoc:
+        Thread.current["#{self}_current_scope"] = scope
+      end
+
+      private
+
+      def construct_finder_arel(options = {}, scope = nil)
+        relation = options.is_a?(Hash) ? unscoped.apply_finder_options(options) : options
+        relation = scope.merge(relation) if scope
+        relation
+      end
+
+    end
+
+    def populate_with_current_scope_attributes
+      return unless self.class.scope_attributes?
+
+      self.class.scope_attributes.each do |att,value|
+        send("#{att}=", value) if respond_to?("#{att}=")
+      end
+    end
+
+  end
+end