1 files changed, 88 insertions, 0 deletions
diff --git a/app/graphql/mutations/merge_requests/accept.rb b/app/graphql/mutations/merge_requests/accept.rb
new file mode 100644
index 00000000000..540be7098ac
--- /dev/null
+++ b/app/graphql/mutations/merge_requests/accept.rb
@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+module Mutations
+  module MergeRequests
+    class Accept < Base
+      NOT_MERGEABLE = 'This branch cannot be merged'
+      HOOKS_VALIDATION_ERROR = 'Pre-merge hooks failed'
+      SHA_MISMATCH = 'The merge-head is not at the anticipated SHA'
+      MERGE_FAILED = 'The merge failed'
+      ALREADY_SCHEDULED = 'The merge request is already scheduled to be merged'
+
+      graphql_name 'MergeRequestAccept'
+      authorize :accept_merge_request
+      description <<~DESC
+        Accepts a merge request.
+        When accepted, the source branch will be merged into the target branch, either
+        immediately if possible, or using one of the automatic merge strategies.
+      DESC
+
+      argument :strategy,
+               ::Types::MergeStrategyEnum,
+               required: false,
+               as: :auto_merge_strategy,
+               description: 'How to merge this merge request.'
+
+      argument :commit_message, ::GraphQL::STRING_TYPE,
+               required: false,
+               description: 'Custom merge commit message.'
+      argument :squash_commit_message, ::GraphQL::STRING_TYPE,
+               required: false,
+               description: 'Custom squash commit message (if squash is true).'
+      argument :sha, ::GraphQL::STRING_TYPE,
+               required: true,
+               description: 'The HEAD SHA at the time when this merge was requested.'
+
+      argument :should_remove_source_branch, ::GraphQL::BOOLEAN_TYPE,
+               required: false,
+               description: 'Should the source branch be removed.'
+      argument :squash, ::GraphQL::BOOLEAN_TYPE,
+               required: false,
+               default_value: false,
+               description: 'Squash commits on the source branch before merge.'
+
+      def resolve(project_path:, iid:, **args)
+        Gitlab::QueryLimiting.whitelist('https://gitlab.com/gitlab-org/gitlab-foss/issues/42317')
+        merge_request = authorized_find!(project_path: project_path, iid: iid)
+        project = merge_request.target_project
+        merge_params = args.compact.with_indifferent_access
+        merge_service = ::MergeRequests::MergeService.new(project, current_user, merge_params)
+
+        if error = validate(merge_request, merge_service, merge_params)
+          return { merge_request: merge_request, errors: [error] }
+        end
+
+        merge_request.update(merge_error: nil, squash: merge_params[:squash])
+
+        result = if merge_params.key?(:auto_merge_strategy)
+                   service = AutoMergeService.new(project, current_user, merge_params)
+                   service.execute(merge_request, merge_params[:auto_merge_strategy])
+                 else
+                   merge_service.execute(merge_request)
+                 end
+
+        {
+          merge_request: merge_request,
+          errors: result == :failed ? [MERGE_FAILED] : []
+        }
+      rescue ::MergeRequests::MergeBaseService::MergeError => e
+        {
+          merge_request: merge_request,
+          errors: [e.message]
+        }
+      end
+
+      def validate(merge_request, merge_service, merge_params)
+        if merge_request.auto_merge_enabled?
+          ALREADY_SCHEDULED
+        elsif !merge_request.mergeable?(skip_ci_check: merge_params.key?(:auto_merge_strategy))
+          NOT_MERGEABLE
+        elsif !merge_service.hooks_validation_pass?(merge_request)
+          HOOKS_VALIDATION_ERROR
+        elsif merge_params[:sha] != merge_request.diff_head_sha
+          SHA_MISMATCH
+        end
+      end
+    end
+  end
+end