Fix 404 when upstream has disabled merge requests

5 files changed, 22 insertions, 3 deletions

diff --git a/app/helpers/merge_requests_helper.rb b/app/helpers/merge_requests_helper.rb
index e347f61fb8d..2614cdfe90e 100644
--- a/app/helpers/merge_requests_helper.rb
+++ b/app/helpers/merge_requests_helper.rb
@@ -1,6 +1,6 @@
 module MergeRequestsHelper
   def new_mr_path_from_push_event(event)
-    target_project = event.project.forked_from_project || event.project
+    target_project = event.project.default_merge_request_target
     new_namespace_project_merge_request_path(
       event.project.namespace,
       event.project,
@@ -127,6 +127,10 @@ module MergeRequestsHelper
     end
   end
 
+  def target_projects(project)
+    [project, project.default_merge_request_target].uniq
+  end
+
   def merge_request_button_visibility(merge_request, closed)
     return 'hidden' if merge_request.closed? == closed || (merge_request.merged? == closed && !merge_request.closed?) || merge_request.closed_without_fork?
   end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 9d2288c311e..365fa4f1e70 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -100,6 +100,7 @@ class MergeRequest < ActiveRecord::Base
   validates :merge_user, presence: true, if: :merge_when_pipeline_succeeds?, unless: :importing?
   validate :validate_branches, unless: [:allow_broken, :importing?, :closed_without_fork?]
   validate :validate_fork, unless: :closed_without_fork?
+  validate :validate_target_project, on: :create
 
   scope :by_source_or_target_branch, ->(branch_name) do
     where("source_branch = :branch OR target_branch = :branch", branch: branch_name)
@@ -330,6 +331,12 @@ class MergeRequest < ActiveRecord::Base
     end
   end
 
+  def validate_target_project
+    return true if target_project.merge_requests_enabled?
+
+    errors.add :base, 'Target project has disabled merge requests'
+  end
+
   def validate_fork
     return true unless target_project && source_project
     return true if target_project == source_project
diff --git a/app/models/project.rb b/app/models/project.rb
index c7dc562c238..9d64e5d406d 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -1314,6 +1314,14 @@ class Project < ActiveRecord::Base
     namespace_id_changed?
   end
 
+  def default_merge_request_target
+    if forked_from_project&.merge_requests_enabled?
+      forked_from_project
+    else
+      self
+    end
+  end
+
   alias_method :name_with_namespace, :full_name
   alias_method :human_name, :full_name
   alias_method :path_with_namespace, :full_path
diff --git a/app/services/merge_requests/build_service.rb b/app/services/merge_requests/build_service.rb
index d45da5180e1..bc0e7ad4e39 100644
--- a/app/services/merge_requests/build_service.rb
+++ b/app/services/merge_requests/build_service.rb
@@ -28,7 +28,7 @@ module MergeRequests
 
     def find_target_project
       return target_project if target_project.present? && can?(current_user, :read_project, target_project)
-      project.forked_from_project || project
+      project.default_merge_request_target
     end
 
     def find_target_branch
diff --git a/app/views/projects/merge_requests/_new_compare.html.haml b/app/views/projects/merge_requests/_new_compare.html.haml
index 8d134aaac67..9cf24e10842 100644
--- a/app/views/projects/merge_requests/_new_compare.html.haml
+++ b/app/views/projects/merge_requests/_new_compare.html.haml
@@ -38,7 +38,7 @@
         .panel-heading
           Target branch
         .panel-body.clearfix
-          - projects =  @project.forked_from_project.nil? ? [@project] : [@project, @project.forked_from_project]
+          - projects = target_projects(@project)
           .merge-request-select.dropdown
             = f.hidden_field :target_project_id
             = dropdown_toggle f.object.target_project.path_with_namespace, { toggle: "dropdown", field_name: "#{f.object_name}[target_project_id]", disabled: @merge_request.persisted? }, { toggle_class: "js-compare-dropdown js-target-project" }