Many to many #clear no longer deletes documents:

- This simply nullifies the relation to be consistent with AR behaviour.
- For previous behaviour of #clear, please use #purge.
- Fixes #988.

lib/mongoid/relations/referenced/many.rb

@@ -60,23 +60,6 @@ def build(attributes = {}, type = nil)
         end
         alias :new :build
 
-        # Clear the relation. Will delete the documents from the db if they are
-        # already persisted.
-        #
-        # @example Clear the relation.
-        #   person.posts.clear
-        #
-        # @return [ Many ] The relation emptied.
-        #
-        # @since 2.0.0.beta.1
-        def clear
-          criteria.delete_all
-          target.clear do |doc|
-            unbind_one(doc)
-            doc.destroyed = true
-          end
-        end
-
         # Creates a new document on the references many relation. This will
         # save the document if the parent has been persisted.
         #
@@ -259,6 +242,24 @@ def nullify
         end
         alias :nullify_all :nullify
 
+        # Clear the relation. Will delete the documents from the db if they are
+        # already persisted.
+        #
+        # @example Clear the relation.
+        #   person.posts.clear
+        #
+        # @return [ Many ] The relation emptied.
+        #
+        # @since 2.0.0.beta.1
+        def purge
+          criteria.delete_all
+          target.clear do |doc|
+            unbind_one(doc)
+            doc.destroyed = true
+          end
+        end
+        alias :clear :purge
+
         # Substitutes the supplied target documents for the existing documents
         # in the relation. If the new target is nil, perform the necessary
         # deletion.
@@ -273,7 +274,7 @@ def nullify
         # @since 2.0.0.rc.1
         def substitute(replacement)
           tap do |proxy|
-            proxy.clear
+            proxy.purge
             proxy.push(replacement) if replacement
           end
         end

lib/mongoid/relations/referenced/many_to_many.rb

@@ -171,14 +171,19 @@ def initialize(base, target, metadata)
         #
         # @since 2.0.0.rc.1
         def nullify
-          # @todo: Durran: This is wrong.
-          criteria.update(metadata.inverse_foreign_key => [])
-          # We need to update the inverse as well.
+          criteria.pull(metadata.inverse_foreign_key, base.id)
+          unless base.destroyed?
+            base.set(
+              metadata.foreign_key,
+              base.send(metadata.foreign_key).clear
+            )
+          end
           target.clear do |doc|
             unbind_one(doc)
           end
         end
         alias :nullify_all :nullify
+        alias :clear :nullify
 
         private
 

spec/functional/mongoid/relations/referenced/many_to_many_spec.rb

@@ -705,11 +705,11 @@
             preference.person_ids.should_not include(person.id)
           end
 
-          it "marks the documents as deleted" do
-            preference.should be_destroyed
+          it "does not delete the documents" do
+            preference.should_not be_destroyed
           end
 
-          it "deletes the documents from the db" do
+          it "persists the nullification" do
             person.reload.preferences.should be_empty
           end