CanCanCommunity/cancancan · error · CanCan::NotImplemented

This model adapter does not support matching on a specific c

Error message

This model adapter does not support matching on a specific condition.

What it means

AbstractAdapter#matches_condition? (lib/cancan/model_adapters/abstract_adapter.rb:63) raises CanCan::NotImplemented. It is only called when the adapter's override_condition_matching?(subject, name, value) returns true — the per-condition override hook — so this error means an adapter promised per-condition matching for some (subject, attribute) pair but never implemented the method.

Source

Thrown at lib/cancan/model_adapters/abstract_adapter.rb:63

      # If this returns true then nested_subject_matches_conditions? will be called.
      def self.override_nested_subject_conditions_matching?(_parent, _child, _all_conditions)
        false
      end

      # Override if override_nested_subject_conditions_matching? returns true
      def self.nested_subject_matches_conditions?(_parent, _child, _all_conditions)
        raise NotImplemented, 'This model adapter does not support matching on a nested subject.'
      end

      # Used to determine if this model adapter will override the matching behavior for a specific condition.
      # If this returns true then matches_condition? will be called. See Rule#matches_conditions_hash
      def self.override_condition_matching?(_subject, _name, _value)
        false
      end

      # Override if override_condition_matching? returns true
      def self.matches_condition?(_subject, _name, _value)
        raise NotImplemented, 'This model adapter does not support matching on a specific condition.'
      end

      def initialize(model_class, rules)
        @model_class = model_class
        @rules = rules
      end

      def database_records
        # This should be overridden in a subclass to return records which match @rules
        raise NotImplemented, 'This model adapter does not support fetching records from the database.'
      end
    end
  end
end

View on GitHub (pinned to 8c1bf153a3)

Solutions

Implement self.matches_condition?(subject, name, value) for every (name, value) shape your override_condition_matching? claims.
Or narrow override_condition_matching? so it returns true only for the cases you actually handle, letting others fall through to default matching.
If using a third-party adapter: upgrade it or replace the exotic condition with a plain attribute/block condition.

Example fix

# before (custom adapter)
def self.override_condition_matching?(_subject, name, _value)
  true # claims every condition, implements none
end

# after
def self.override_condition_matching?(_subject, name, _value)
  false # default matching handles regular columns
end
# and only flip to true for specific names you implement in
# def self.matches_condition?(subject, name, value); ...; end

Defensive patterns

Strategy: validation

Validate before calling

# adapter authors: scope the claim to conditions you really implement
class MyAdapter < CanCan::ModelAdapters::AbstractAdapter
  HANDLED = %i[geometry].freeze
  def self.override_condition_matching?(_subject, name, _value)
    HANDLED.include?(name.to_sym) # false elsewhere -> default matching
  end
end

Type guard

def adapter_supports_condition?(adapter, subject, name, value)
  !adapter.override_condition_matching?(subject, name, value) || adapter.method(:matches_condition?).owner != CanCan::ModelAdapters::AbstractAdapter
end

Try / catch

begin
  can?(:read, @map)
rescue CanCan::NotImplemented => e
  Rails.logger.error("adapter incomplete: #{e.message}")
  false
end

Prevention

Never return true unconditionally from override_condition_matching?.
Pair every override_condition_matching? branch with a spec for matches_condition?.
Replace exotic conditions with plain attributes or blocks when the adapter cannot match them.

When it happens

Trigger: A custom adapter with special handling like def self.override_condition_matching?(subject, name, value); name == :geometry; end but no matches_condition? implementation; then a rule containing that condition (can :read, Map, geometry: polygon) is instance-checked via can?/authorize!.

Common situations: Adapters adding support for non-column condition types (arrays, JSON columns, geo types) and forgetting the matcher half of the pair; partial vendored forks of the ActiveRecord adapter.

Related errors

AI-assisted analysis of CanCanCommunity/cancancan@8c1bf153a3 (2026-08-21). Data as JSON: /api/errors/d9a8852ced9e5588. Report an issue: GitHub.