Raise error when using invalid relation type in member finder

Adds a check in the GroupMembersFinder to raise ArgumentError
if using an invalid value in the include_relations argument.

Currently this just fails silently in the case of a typo.

app/finders/group_members_finder.rb

@@ -3,6 +3,7 @@
 class GroupMembersFinder < UnionFinder
   RELATIONS = %i(direct inherited descendants).freeze
   DEFAULT_RELATIONS = %i(direct inherited).freeze
+  INVALID_RELATION_TYPE_ERROR_MSG = "is not a valid relation type. Valid relation types are #{RELATIONS.join(', ')}."
 
   RELATIONS_DESCRIPTIONS = {
     direct: 'Members in the group itself',
@@ -42,6 +43,8 @@ class GroupMembersFinder < UnionFinder
   attr_reader :user, :group
 
   def groups_by_relations(include_relations)
+    check_relation_arguments!(include_relations)
+
     case include_relations.sort
     when [:inherited]
       group.ancestors
@@ -86,6 +89,12 @@ class GroupMembersFinder < UnionFinder
   def members_of_groups(groups)
     GroupMember.non_request.of_groups(groups)
   end
+
+  def check_relation_arguments!(include_relations)
+    unless include_relations & RELATIONS == include_relations
+      raise ArgumentError, "#{(include_relations - RELATIONS).first} #{INVALID_RELATION_TYPE_ERROR_MSG}"
+    end
+  end
 end
 
 GroupMembersFinder.prepend_mod_with('GroupMembersFinder')

spec/finders/group_members_finder_spec.rb

@@ -38,6 +38,12 @@ RSpec.describe GroupMembersFinder, '#execute' do
       }
     end
 
+    it 'raises an error if a non-supported relation type is used' do
+      expect do
+        described_class.new(group).execute(include_relations: [:direct, :invalid_relation_type])
+      end.to raise_error(ArgumentError, "invalid_relation_type is not a valid relation type. Valid relation types are direct, inherited, descendants.")
+    end
+
     using RSpec::Parameterized::TableSyntax
 
     where(:subject_relations, :subject_group, :expected_members) do