API: refactored and simplified error handling in merge requests API

lib/api/merge_requests.rb

@@ -4,21 +4,12 @@ module Gitlab
     before { authenticate! }
     resource :projects do
-
       helpers do
-        # If an error occurred this helper method provides an appropriate status code
-        #
-        # Parameters:
-        #   merge_request_errors (required) - The errors collection of MR
-        #
-        def handle_merge_request_error(merge_request_errors)
-          if merge_request_errors[:target_branch].any?
-            bad_request!(:target_branch)
-          elsif merge_request_errors[:source_branch].any?
-            bad_request!(:source_branch)
-          elsif merge_request_errors[:base].any?
-            error!(merge_request_errors[:base], 422)
+        def handle_merge_request_errors!(errors)
+          if errors[:project_access].any?
+            error!(errors[:project_access], 422)
           end
+          not_found!
         end
       end
@@ -78,8 +69,7 @@ module Gitlab
           merge_request.reload_code
           present merge_request, with: Entities::MergeRequest
         else
-          handle_merge_request_error(merge_request.errors)
-          not_found!
+          handle_merge_request_errors! merge_request.errors
         end
       end
@@ -107,8 +97,7 @@ module Gitlab
           merge_request.mark_as_unchecked
           present merge_request, with: Entities::MergeRequest
         else
-          handle_merge_request_error(merge_request.errors)
-          not_found!
+          handle_merge_request_errors! merge_request.errors
         end
       end

lib/api/projects.rb

@@ -233,7 +233,7 @@ module Gitlab
         end
       end
-      # Delete project hook
+      # Deletes project hook. This is an idempotent function.
       #
       # Parameters:
       #   id (required) - The ID of a project
@@ -248,6 +248,7 @@ module Gitlab
           @hook = ProjectHook.find(params[:hook_id])
           @hook.destroy
         rescue
+          # ProjectHook can raise Error if hook_id not found
         end
       end