API: extracted helper method to provide 400 bad request error with description

Extracted a method for 400 error (Bad request) and adjusted code accordingly. The name of
the missing attribute is used to show which one was missing from the request. It is used to
give an appropriate message in the json response.

lib/api/helpers.rb

@@ -55,6 +55,12 @@ module Gitlab
       render_api_error!('403 Forbidden', 403)
     end
+    def bad_request!(attribute)
+      message = ["400 (Bad request)"]
+      message << "\"" + attribute.to_s + "\" not given"
+      render_api_error!(message.join(' '), 400)
+    end
+
     def not_found!(resource = nil)
       message = ["404"]
       message << resource if resource

lib/api/merge_requests.rb

@@ -13,9 +13,9 @@ module Gitlab
         #
         def handle_merge_request_error(merge_request_errors)
           if merge_request_errors[:target_branch].any?
-            error!(merge_request_errors[:target_branch], 400)
+            bad_request!(:target_branch)
           elsif merge_request_errors[:source_branch].any?
-            error!(merge_request_errors[:source_branch], 400)
+            bad_request!(:source_branch)
           elsif merge_request_errors[:base].any?
             error!(merge_request_errors[:base], 422)
           end
@@ -129,7 +129,7 @@ module Gitlab
           present note, with: Entities::MRNote
         else
           if note.errors[:note].any?
-            error!(note.errors[:note], 400)
+            bad_request!(:note)
           end
           not_found!
         end

lib/api/milestones.rb

@@ -13,7 +13,7 @@ module Gitlab
         #
         def handle_milestone_errors(milestone_errors)
           if milestone_errors[:title].any?
-            error!(milestone_errors[:title], 400)
+            bad_request!(:title)
           end
         end
       end

lib/api/notes.rb

@@ -44,7 +44,7 @@ module Gitlab
           present @note, with: Entities::Note
         else
           # :note is exposed as :body, but :note is set on error
-          error!(@note.errors[:note], 400) if @note.errors[:note].any?
+          bad_request!(:note) if @note.errors[:note].any?
           not_found!
         end
       end

lib/api/projects.rb

@@ -45,7 +45,7 @@ module Gitlab
       # Example Request
       #   POST /projects
       post do
-        error!("Name is required", 400) if !params.has_key? :name
+        bad_request!(:name) if !params.has_key? :name
         attrs = attributes_for_keys [:name,
                                     :description,
                                     :default_branch,
@@ -101,8 +101,8 @@ module Gitlab
       post ":id/members" do
         authorize! :admin_project, user_project
-        error!("User id not given", 400) if !params.has_key? :user_id
-        error!("Access level not given", 400) if !params.has_key? :access_level
+        bad_request!(:user_id) if !params.has_key? :user_id
+        bad_request!(:access_level) if !params.has_key? :access_level
         # either the user is already a team member or a new one
         team_member = user_project.team_member_by_id(params[:user_id])
@@ -133,8 +133,8 @@ module Gitlab
         authorize! :admin_project, user_project
         team_member = user_project.users_projects.find_by_user_id(params[:user_id])
-        error!("Access level not given", 400) if !params.has_key? :access_level
-        error!("User can not be found", 404) if team_member.nil?
+        bad_request!(:access_level) if !params.has_key? :access_level
+        not_found!("User can not be found") if team_member.nil?
         if team_member.update_attributes(project_access: params[:access_level])
           @member = team_member.user
@@ -196,7 +196,7 @@ module Gitlab
       post ":id/hooks" do
         authorize! :admin_project, user_project
-        error!("Url not given", 400) unless params.has_key? :url
+        bad_request!(:url) unless params.has_key? :url
         @hook = user_project.hooks.new({"url" => params[:url]})
         if @hook.save
@@ -218,7 +218,7 @@ module Gitlab
         @hook = user_project.hooks.find(params[:hook_id])
         authorize! :admin_project, user_project
-        error!("Url not given", 400) unless params.has_key? :url
+        bad_request!(:url) unless params.has_key? :url
         attrs = attributes_for_keys [:url]
         if @hook.update_attributes attrs
@@ -237,7 +237,7 @@ module Gitlab
       #   DELETE /projects/:id/hooks
       delete ":id/hooks" do
         authorize! :admin_project, user_project
-        error!("Hook id not given", 400) unless params.has_key? :hook_id
+        bad_request!(:hook_id) unless params.has_key? :hook_id
         begin
           @hook = ProjectHook.find(params[:hook_id])
@@ -368,9 +368,9 @@ module Gitlab
       post ":id/snippets" do
         authorize! :write_snippet, user_project
-        error!("Title not given", 400) if !params[:title].present?
-        error!("Filename not given", 400) if !params[:file_name].present?
-        error!("Code not given", 400) if !params[:code].present?
+        bad_request!(:title) if !params[:title].present?
+        bad_request!(:file_name) if !params[:file_name].present?
+        bad_request!(:code) if !params[:code].present?
         attrs = attributes_for_keys [:title, :file_name]
         attrs[:expires_at] = params[:lifetime] if params[:lifetime].present?
@@ -451,7 +451,7 @@ module Gitlab
       get ":id/repository/commits/:sha/blob" do
         authorize! :download_code, user_project
-        error!("Filepath must be specified", 400) if !params.has_key? :filepath
+        bad_request!(:filepath) if !params.has_key? :filepath
         ref = params[:sha]

spec/requests/api/merge_requests_spec.rb

@@ -32,6 +32,11 @@ describe Gitlab::API do
       response.status.should == 200
       json_response['title'].should == merge_request.title
     end
+
+    it "should return a 404 error if merge_request_id not found" do
+      get api("/projects/#{project.id}/merge_request/999", user)
+      response.status.should == 404
+    end
   end
   describe "POST /projects/:id/merge_requests" do