Fix bug for repeated fork requests

When asking to fork a project and a project with the same name
already exists (likely from a previous fork), the recovery from
the fork failure would inadvertantly delete the repo of the
existing destination project.

app/contexts/projects/fork_context.rb

@@ -12,10 +12,15 @@ module Projects
       project.name = @from_project.name
       project.path = @from_project.path
       project.namespace = current_user.namespace
+      project.creator = current_user
 
+      # If the project cannot save, we do not want to trigger the project destroy
+      # as this can have the side effect of deleting a repo attached to an existing
+      # project with the same name and namespace
+      if project.valid?
+        begin
           Project.transaction do
             #First save the DB entries as they can be rolled back if the repo fork fails
-        project.creator = current_user
             project.build_forked_project_link(forked_to_project_id: project.id, forked_from_project_id: @from_project.id)
             if project.save
               project.users_projects.create(project_access: UsersProject::MASTER, user: current_user)
@@ -25,13 +30,16 @@ module Projects
               raise "forking failed in gitlab-shell"
             end
             project.ensure_satellite_exists
-
           end
-      project
         rescue => ex
-      project.errors.add(:base, "Can't fork project. Please try again later")
+          project.errors.add(:base, "Fork transaction failed.")
           project.destroy
         end
+      else
+        project.errors.add(:base, "Invalid fork destination")
+      end
+      project
 
     end
+  end
 end

spec/contexts/fork_context_spec.rb

@@ -3,29 +3,45 @@ require 'spec_helper'
 describe Projects::ForkContext do
   describe :fork_by_user do
     before do
-      @from_user = create :user
-      @from_project = create(:project, creator_id: @from_user.id)
-      @to_user = create :user
+      @from_namespace = create(:namespace)
+      @from_user = create(:user, namespace: @from_namespace )
+      @from_project = create(:project, creator_id: @from_user.id, namespace: @from_namespace)
+      @to_namespace = create(:namespace)
+      @to_user = create(:user, namespace: @to_namespace)
     end
 
     context 'fork project' do
-      before do
+
+      it "successfully creates project in the user namespace" do
         @to_project = fork_project(@from_project, @to_user)
-      end
 
-      it { @to_project.owner.should == @to_user }
-      it { @to_project.namespace.should == @to_user.namespace }
+        @to_project.owner.should == @to_user
+        @to_project.namespace.should == @to_user.namespace
+      end
     end
 
     context 'fork project failure' do
-      before do
-        #corrupt the project so the attempt to fork will fail
-        @from_project = create(:project, path: "empty")
+
+      it "fails due to transaction failure" do
+        # make the mock gitlab-shell fail
         @to_project = fork_project(@from_project, @to_user, false)
+
+        @to_project.errors.should_not be_empty
+        @to_project.errors[:base].should include("Fork transaction failed.")
       end
 
-      it {@to_project.errors.should_not be_empty}
-      it {@to_project.errors[:base].should include("Can't fork project. Please try again later") }
+    end
+
+    context 'project already exists' do
+
+      it "should fail due to validation, not transaction failure" do
+        @existing_project = create(:project, creator_id: @to_user.id, name: @from_project.name, namespace: @to_namespace)
+        @to_project = fork_project(@from_project, @to_user)
+
+        @existing_project.persisted?.should be_true
+        @to_project.errors[:base].should include("Invalid fork destination")
+        @to_project.errors[:base].should_not include("Fork transaction failed.")
+      end
 
     end
   end