Merge branch 'osw-sync-merge-ref-upon-mergeability-check' into 'master'

Automatically update MR merge-ref along merge status

Closes #58495

See merge request gitlab-org/gitlab-ce!28513

2 files changed, 85 insertions, 17 deletions

diff --git a/app/services/merge_requests/merge_to_ref_service.rb b/app/services/merge_requests/merge_to_ref_service.rb
index 87147d90c32..8670b9ccf3d 100644
--- a/app/services/merge_requests/merge_to_ref_service.rb
+++ b/app/services/merge_requests/merge_to_ref_service.rb
@@ -20,20 +20,14 @@ module MergeRequests
 
       raise_error('Conflicts detected during merge') unless commit_id
 
-      commit = project.commit(commit_id)
-      target_id, source_id = commit.parent_ids
-
-      success(commit_id: commit.id,
-              target_id: target_id,
-              source_id: source_id)
-    rescue MergeError => error
+      success(commit_id: commit_id)
+    rescue MergeError, ArgumentError => error
       error(error.message)
     end
 
     private
 
     def validate!
-      authorization_check!
       error_check!
     end
 
@@ -43,21 +37,13 @@ module MergeRequests
       error =
         if !hooks_validation_pass?(merge_request)
           hooks_validation_error(merge_request)
-        elsif !@merge_request.mergeable_to_ref?
-          "Merge request is not mergeable to #{target_ref}"
-        elsif !source
+        elsif source.blank?
           'No source for merge'
         end
 
       raise_error(error) if error
     end
 
-    def authorization_check!
-      unless Ability.allowed?(current_user, :admin_merge_request, project)
-        raise_error("You are not allowed to merge to this ref")
-      end
-    end
-
     def target_ref
       merge_request.merge_ref_path
     end
diff --git a/app/services/merge_requests/mergeability_check_service.rb b/app/services/merge_requests/mergeability_check_service.rb
new file mode 100644
index 00000000000..ef833774e65
--- /dev/null
+++ b/app/services/merge_requests/mergeability_check_service.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+module MergeRequests
+  class MergeabilityCheckService < ::BaseService
+    include Gitlab::Utils::StrongMemoize
+
+    delegate :project, to: :@merge_request
+    delegate :repository, to: :project
+
+    def initialize(merge_request)
+      @merge_request = merge_request
+    end
+
+    # Updates the MR merge_status. Whenever it switches to a can_be_merged state,
+    # the merge-ref is refreshed.
+    #
+    # Returns a ServiceResponse indicating merge_status is/became can_be_merged
+    # and the merge-ref is synced. Success in case of being/becoming mergeable,
+    # error otherwise.
+    def execute
+      return ServiceResponse.error(message: 'Invalid argument') unless merge_request
+      return ServiceResponse.error(message: 'Unsupported operation') if Gitlab::Database.read_only?
+
+      update_merge_status
+
+      unless merge_request.can_be_merged?
+        return ServiceResponse.error(message: 'Merge request is not mergeable')
+      end
+
+      unless payload.fetch(:merge_ref_head)
+        return ServiceResponse.error(message: 'Merge ref was not found')
+      end
+
+      ServiceResponse.success(payload: payload)
+    end
+
+    private
+
+    attr_reader :merge_request
+
+    def payload
+      strong_memoize(:payload) do
+        {
+          merge_ref_head: merge_ref_head_payload
+        }
+      end
+    end
+
+    def merge_ref_head_payload
+      commit = merge_request.merge_ref_head
+
+      return unless commit
+
+      target_id, source_id = commit.parent_ids
+
+      {
+        commit_id: commit.id,
+        source_id: source_id,
+        target_id: target_id
+      }
+    end
+
+    def update_merge_status
+      return unless merge_request.recheck_merge_status?
+
+      if can_git_merge?
+        merge_to_ref && merge_request.mark_as_mergeable
+      else
+        merge_request.mark_as_unmergeable
+      end
+    end
+
+    def can_git_merge?
+      !merge_request.broken? && repository.can_be_merged?(merge_request.diff_head_sha, merge_request.target_branch)
+    end
+
+    def merge_to_ref
+      result = MergeRequests::MergeToRefService.new(project, merge_request.author).execute(merge_request)
+      result[:status] == :success
+    end
+  end
+end