{"record":{"id":"2c96037c423275b1","repo":"mongodb/mongoid","slug":"the-fallback-option-for-association-name-on-2c9603","errorCode":null,"errorMessage":"The :fallback option for association '#{name}' on #{@owner_class} cannot be combined with :autobuild.","messagePattern":"The :fallback option for association '#(.+?)' on #(.+?) cannot be combined with :autobuild\\.","errorType":"exception","errorClass":"ArgumentError","httpStatus":null,"severity":"error","filePath":"lib/mongoid/association/relatable.rb","lineNumber":433,"sourceCode":"        Association::Depending.define_dependency!(self)\n      end\n\n      def validate!\n        @options.keys.each do |opt|\n          unless self.class::VALID_OPTIONS.include?(opt)\n            raise Errors::InvalidRelationOption.new(@owner_class, name, opt, self.class::VALID_OPTIONS)\n          end\n        end\n\n        if @options.key?(:fallback)\n          unless @options[:fallback].respond_to?(:call)\n            raise ArgumentError,\n                  \"The :fallback option for association '#{name}' on \" \\\n                  \"#{@owner_class} must be a Proc or lambda.\"\n          end\n\n          if @options.key?(:autobuild)\n            raise ArgumentError,\n                  \"The :fallback option for association '#{name}' on \" \\\n                  \"#{@owner_class} cannot be combined with :autobuild.\"\n          end\n        end\n\n        [ name, :\"#{name}?\", :\"#{name}=\" ].each do |n|\n          raise Errors::InvalidRelation.new(@owner_class, n) if Mongoid.destructive_fields.include?(n)\n        end\n      end\n\n      def polymorph!\n        return unless polymorphic?\n\n        @owner_class.polymorphic = true\n      end\n\n      def create_extension!(&block)\n        return unless block","sourceCodeStart":415,"sourceCodeEnd":451,"githubUrl":"https://github.com/mongodb/mongoid/blob/0da0e23d71adfbad31128c18e5e2c8c301c6f7c4/lib/mongoid/association/relatable.rb#L415-L451","documentation":"Error \"The :fallback option for association '#{name}' on #{@owner_class} cannot be combined with :autobuild.\" thrown in mongodb/mongoid.","triggerScenarios":"Thrown at lib/mongoid/association/relatable.rb:433 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"0da0e23d71adfbad31128c18e5e2c8c301c6f7c4","analyzedAt":"2026-08-23T06:25:47.656Z","schemaVersion":2},"datasetVersion":"2026-08-23T08:06:27.607Z"}