Allow Members::ApproveAccessRequestService to accept a new :force param

This param allows to bypass permission check. It is useful for LDAP-sync
where even owners don't have the :admin_group_member permission.

See
https://gitlab.com/gitlab-org/gitlab-ee/blob/6081c37123abae4570f78831b33c2f45f92c2765/app/policies/group_policy.rb#L38
and https://gitlab.com/gitlab-org/gitlab-ee/issues/1159Signed-off-by: Rémy Coutable <remy@rymai.me>

app/services/members/approve_access_request_service.rb

@@ -4,17 +4,25 @@ module Members
 
     attr_accessor :source
 
+    # source - The source object that respond to `#requesters` (i.g. project or group)
+    # current_user - The user that performs the access request approval
+    # params - A hash of parameters
+    #   :user_id - User ID used to retrieve the access requester
+    #   :id - Member ID used to retrieve the access requester
+    #   :access_level - Optional access level set when the request is accepted
     def initialize(source, current_user, params = {})
       @source = source
       @current_user = current_user
-      @params = params
+      @params = params.slice(:user_id, :id, :access_level)
     end
 
-    def execute
+    # opts - A hash of options
+    #   :force - Bypass permission check: current_user can be nil in that case
+    def execute(opts = {})
       condition = params[:user_id] ? { user_id: params[:user_id] } : { id: params[:id] }
       access_requester = source.requesters.find_by!(condition)
 
-      raise Gitlab::Access::AccessDeniedError unless can_update_access_requester?(access_requester)
+      raise Gitlab::Access::AccessDeniedError unless can_update_access_requester?(access_requester, opts)
 
       access_requester.access_level = params[:access_level] if params[:access_level]
       access_requester.accept_request
@@ -24,8 +32,11 @@ module Members
 
     private
 
-    def can_update_access_requester?(access_requester)
-      access_requester && can?(current_user, action_member_permission(:update, access_requester), access_requester)
+    def can_update_access_requester?(access_requester, opts = {})
+      access_requester && (
+        opts[:force] ||
+        can?(current_user, action_member_permission(:update, access_requester), access_requester)
+      )
     end
   end
 end

spec/services/members/approve_access_request_service_spec.rb

@@ -5,36 +5,37 @@ describe Members::ApproveAccessRequestService, services: true do
   let(:access_requester) { create(:user) }
   let(:project) { create(:project, :public) }
   let(:group) { create(:group, :public) }
+  let(:opts) { {} }
 
   shared_examples 'a service raising ActiveRecord::RecordNotFound' do
     it 'raises ActiveRecord::RecordNotFound' do
-      expect { described_class.new(source, user, params).execute }.to raise_error(ActiveRecord::RecordNotFound)
+      expect { described_class.new(source, user, params).execute(opts) }.to raise_error(ActiveRecord::RecordNotFound)
     end
   end
 
   shared_examples 'a service raising Gitlab::Access::AccessDeniedError' do
     it 'raises Gitlab::Access::AccessDeniedError' do
-      expect { described_class.new(source, user, params).execute }.to raise_error(Gitlab::Access::AccessDeniedError)
+      expect { described_class.new(source, user, params).execute(opts) }.to raise_error(Gitlab::Access::AccessDeniedError)
     end
   end
 
   shared_examples 'a service approving an access request' do
     it 'succeeds' do
-      expect { described_class.new(source, user, params).execute }.to change { source.requesters.count }.by(-1)
+      expect { described_class.new(source, user, params).execute(opts) }.to change { source.requesters.count }.by(-1)
     end
 
     it 'returns a <Source>Member' do
-      member = described_class.new(source, user, params).execute
+      member = described_class.new(source, user, params).execute(opts)
 
       expect(member).to be_a "#{source.class}Member".constantize
       expect(member.requested_at).to be_nil
     end
 
     context 'with a custom access level' do
-      let(:params) { { user_id: access_requester.id, access_level: Gitlab::Access::MASTER } }
+      let(:params2) { params.merge(user_id: access_requester.id, access_level: Gitlab::Access::MASTER) }
 
       it 'returns a ProjectMember with the custom access level' do
-        member = described_class.new(source, user, params).execute
+        member = described_class.new(source, user, params2).execute(opts)
 
         expect(member.access_level).to eq Gitlab::Access::MASTER
       end
@@ -60,6 +61,56 @@ describe Members::ApproveAccessRequestService, services: true do
     end
     let(:params) { { user_id: access_requester.id } }
 
+    context 'when current user is nil' do
+      let(:user) { nil }
+
+      context 'and :force option is not given' do
+        it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
+          let(:source) { project }
+        end
+
+        it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
+          let(:source) { group }
+        end
+      end
+
+      context 'and :force option is false' do
+        let(:opts) { { force: false } }
+
+        it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
+          let(:source) { project }
+        end
+
+        it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
+          let(:source) { group }
+        end
+      end
+
+      context 'and :force option is true' do
+        let(:opts) { { force: true } }
+
+        it_behaves_like 'a service approving an access request' do
+          let(:source) { project }
+        end
+
+        it_behaves_like 'a service approving an access request' do
+          let(:source) { group }
+        end
+      end
+
+      context 'and :force param is true' do
+        let(:params) { { user_id: access_requester.id, force: true } }
+
+        it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
+          let(:source) { project }
+        end
+
+        it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
+          let(:source) { group }
+        end
+      end
+    end
+
     context 'when current user cannot approve access request to the project' do
       it_behaves_like 'a service raising Gitlab::Access::AccessDeniedError' do
         let(:source) { project }