Merge branch '21513-fix-branch-protection-api' into 'master'

Fix branch protection API.

## What does this MR do?

- Fixes the branch protection API.
- Closes #21513 
- EE Merge Request: gitlab-org/gitlab-ee!718

## Tasks

- [ ]  #21513 !6215 Protected branches API bug
    - [x]  Investigate
    - [x]  Test + Fix
    - [x]  Changelog
    - [x]  MR
    - [x]  Wait for build to pass
    - [x]  Review
    - [x]  Check for EE conflicts
    - [x]  Create EE MR
    - [x]  Refactor + Fix
    - [x]  Rebase EE MR against EE master
    - [x]  Wait for builds to pass
    - [x]  Assign to dbalexandre/douwe
    - [x]  Implement latest review comments
    - [x]  Wait for Douwe's review
        - [x]  Implement changes
        - [x]  Port changes to EE MR
        - [x]  Assign both back to Douwe
    - [ ]  Wait for merge
    - [ ]  Merge gitlab-org/gitlab-ee!718

See merge request !6215

1 files changed, 15 insertions, 33 deletions

diff --git a/lib/api/branches.rb b/lib/api/branches.rb
index b615703df93..6d827448994 100644
--- a/lib/api/branches.rb
+++ b/lib/api/branches.rb
@@ -54,43 +54,25 @@ module API
         not_found!('Branch') unless @branch
         protected_branch = user_project.protected_branches.find_by(name: @branch.name)
 
-        developers_can_merge = to_boolean(params[:developers_can_merge])
-        developers_can_push = to_boolean(params[:developers_can_push])
-
         protected_branch_params = {
-          name: @branch.name
+          name: @branch.name,
+          developers_can_push: to_boolean(params[:developers_can_push]),
+          developers_can_merge: to_boolean(params[:developers_can_merge])
         }
 
-        # If `developers_can_merge` is switched off, _all_ `DEVELOPER`
-        # merge_access_levels need to be deleted.
-        if developers_can_merge == false
-          protected_branch.merge_access_levels.where(access_level: Gitlab::Access::DEVELOPER).destroy_all
-        end
+        service_args = [user_project, current_user, protected_branch_params]
 
-        # If `developers_can_push` is switched off, _all_ `DEVELOPER`
-        # push_access_levels need to be deleted.
-        if developers_can_push == false
-          protected_branch.push_access_levels.where(access_level: Gitlab::Access::DEVELOPER).destroy_all
-        end
+        protected_branch = if protected_branch
+                             ProtectedBranches::ApiUpdateService.new(*service_args).execute(protected_branch)
+                           else
+                             ProtectedBranches::ApiCreateService.new(*service_args).execute
+                           end
 
-        protected_branch_params.merge!(
-          merge_access_levels_attributes: [{
-            access_level: developers_can_merge ? Gitlab::Access::DEVELOPER : Gitlab::Access::MASTER
-          }],
-          push_access_levels_attributes: [{
-            access_level: developers_can_push ? Gitlab::Access::DEVELOPER : Gitlab::Access::MASTER
-          }]
-        )
-
-        if protected_branch
-          service = ProtectedBranches::UpdateService.new(user_project, current_user, protected_branch_params)
-          service.execute(protected_branch)
+        if protected_branch.valid?
+          present @branch, with: Entities::RepoBranch, project: user_project
         else
-          service = ProtectedBranches::CreateService.new(user_project, current_user, protected_branch_params)
-          service.execute
+          render_api_error!(protected_branch.errors.full_messages, 422)
         end
-
-        present @branch, with: Entities::RepoBranch, project: user_project
       end
 
       # Unprotect a single branch
@@ -123,7 +105,7 @@ module API
       post ":id/repository/branches" do
         authorize_push_project
         result = CreateBranchService.new(user_project, current_user).
-          execute(params[:branch_name], params[:ref])
+                 execute(params[:branch_name], params[:ref])
 
         if result[:status] == :success
           present result[:branch],
@@ -142,10 +124,10 @@ module API
       # Example Request:
       #   DELETE /projects/:id/repository/branches/:branch
       delete ":id/repository/branches/:branch",
-          requirements: { branch: /.+/ } do
+             requirements: { branch: /.+/ } do
         authorize_push_project
         result = DeleteBranchService.new(user_project, current_user).
-          execute(params[:branch])
+                 execute(params[:branch])
 
         if result[:status] == :success
           {