API: refined status code handling when adding or updating a project member

When a user is added to a project that is already a member of, a status code 201 is now returned to
signal an idempotent operation. If something fails then instead of returning error code 404 different
more specific error codes are returned. Status code 400 (Bad request) is returned when a required
attribute, e.g. `access_level` is not given or 422 if there is a semantic error, e.g. should
the `access_level` have an unsupported value.

Specs are added to check these status codes.

lib/api/projects.rb

@@ -89,15 +89,26 @@ module Gitlab
       #   POST /projects/:id/members
       post ":id/members" do
         authorize! :admin_project, user_project
-        users_project = user_project.users_projects.new(
+
+        error!("User id not given", 400) if !params.has_key? :user_id
+        error!("Access level not given", 400) 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])
+        if team_member.nil?
+          team_member = user_project.users_projects.new(
             user_id: params[:user_id],
             project_access: params[:access_level]
           )
+        end
 
-        if users_project.save
-          @member = users_project.user
+        if team_member.save
+          @member = team_member.user
           present @member, with: Entities::ProjectMember, project: user_project
         else
+          if team_member.errors[:project_access].any?
+            error!(team_member.errors[:project_access], 422)
+          end
           not_found!
         end
       end
@@ -112,12 +123,18 @@ module Gitlab
       #   PUT /projects/:id/members/:user_id
       put ":id/members/:user_id" do
         authorize! :admin_project, user_project
-        users_project = user_project.users_projects.find_by_user_id params[:user_id]
 
-        if users_project.update_attributes(project_access: params[:access_level])
-          @member = users_project.user
+        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?
+
+        if team_member.update_attributes(project_access: params[:access_level])
+          @member = team_member.user
           present @member, with: Entities::ProjectMember, project: user_project
         else
+          if team_member.errors[:project_access].any?
+            error!(team_member.errors[:project_access], 422)
+          end
           not_found!
         end
       end

spec/requests/api/projects_spec.rb

@@ -177,6 +177,34 @@ describe Gitlab::API do
       json_response['email'].should == user2.email
       json_response['access_level'].should == UsersProject::DEVELOPER
     end
+
+    it "should return a 201 status if user is already project member" do
+      post api("/projects/#{project.id}/members", user), user_id: user2.id,
+        access_level: UsersProject::DEVELOPER
+      expect {
+        post api("/projects/#{project.id}/members", user), user_id: user2.id,
+          access_level: UsersProject::DEVELOPER
+      }.not_to change { UsersProject.count }.by(1)
+
+      response.status.should == 201
+      json_response['email'].should == user2.email
+      json_response['access_level'].should == UsersProject::DEVELOPER
+    end
+
+    it "should return a 400 error when user id is not given" do
+      post api("/projects/#{project.id}/members", user), access_level: UsersProject::MASTER
+      response.status.should == 400
+    end
+
+    it "should return a 400 error when access level is not given" do
+      post api("/projects/#{project.id}/members", user), user_id: user2.id
+      response.status.should == 400
+    end
+
+    it "should return a 422 error when access level is not known" do
+      post api("/projects/#{project.id}/members", user), user_id: user2.id, access_level: 1234
+      response.status.should == 422
+    end
   end
 
   describe "PUT /projects/:id/members/:user_id" do
@@ -186,6 +214,21 @@ describe Gitlab::API do
       json_response['email'].should == user3.email
       json_response['access_level'].should == UsersProject::MASTER
     end
+
+    it "should return a 404 error if user_id is not found" do
+      put api("/projects/#{project.id}/members/1234", user), access_level: UsersProject::MASTER
+      response.status.should == 404
+    end
+
+    it "should return a 400 error when access level is not given" do
+      put api("/projects/#{project.id}/members/#{user3.id}", user)
+      response.status.should == 400
+    end
+
+    it "should return a 422 error when access level is not known" do
+      put api("/projects/#{project.id}/members/#{user3.id}", user), access_level: 123
+      response.status.should == 422
+    end
   end
 
   describe "DELETE /projects/:id/members/:user_id" do