ruby-grape/grape · error · Grape::DSL::Declared::MethodNotYetAvailable

#declared is not available prior to parameter validation

Error message

#declared is not available prior to parameter validation

What it means

The `declared` helper returns only the parameters declared via `params` blocks, but that information is only trustworthy after Grape has run the endpoint's filters and parameter validation. `declared` checks `before_filter_passed` and raises Grape::Exceptions::MethodNotYetAvailable ('#declared is not available prior to parameter validation') when it is called earlier in the request lifecycle, typically from inside a `before` block.

Source

Thrown at lib/grape/dsl/declared.rb:23

    module Declared
      # Denotes a situation where a DSL method has been invoked in a
      # filter which it should not yet be available in
      class MethodNotYetAvailable < StandardError
        def initialize(msg = '#declared is not available prior to parameter validation')
          super
        end
      end

      # A filtering method that will return a hash
      # consisting only of keys that have been declared by a
      # `params` statement against the current/target endpoint or parent
      # namespaces.
      # @param params [Hash] The initial hash to filter. Usually this will just be `params`
      # @param options [Hash] Can pass `:include_missing`, `:stringify` and `:include_parent_namespaces`
      # options. `:include_parent_namespaces` defaults to true, hence must be set to false if
      # you want only to return params declared against the current/target endpoint.
      def declared(passed_params, include_parent_namespaces: true, include_missing: true, evaluate_given: false, stringify: false)
        raise MethodNotYetAvailable unless before_filter_passed

        contract_key_map = inheritable_setting.contract_key_maps
        handler = DeclaredParamsHandler.new(include_missing:, evaluate_given:, stringify:, contract_key_map:)
        declared_params = include_parent_namespaces ? inheritable_setting.route_declared_params : (inheritable_setting.declared_params.last || [])
        renamed_params = inheritable_setting.route_renamed_params
        route_params = config.params

        handler.call(passed_params, declared_params, route_params, renamed_params)
      end
    end
  end
end

View on GitHub (pinned to 22d7975629)

Solutions

Move the `declared(params)` call into the route action (the get/post/put block), where validation has already run.
If you only need the raw validated params in the before block, use `params` directly instead of `declared(params)`.
Extract shared logic into a helper method that takes the already-filtered hash and call it from the action after `declared`.

Example fix

# before
before do
  @scoped = declared(params, include_missing: false) # raises MethodNotYetAvailable
end
get '/things' do
  @scoped
end

# after
get '/things' do
  declared(params, include_missing: false)
end

Defensive patterns

Strategy: validation

Validate before calling

# In before blocks, use raw params; declared is only legal in the action
before do
  @raw = params # NOT declared(params)
end

Try / catch

begin
  declared(params, include_missing: false)
rescue Grape::Exceptions::MethodNotYetAvailable
  params # fallback: raw params when called too early (e.g. shared helper)
end

Prevention

Call `declared` only inside route actions, never in `before` or `rescue_from`.
Put shared filtering logic in helpers that accept the filtered hash as an argument.
Add a spec that exercises each `before` block to catch premature helper use.

When it happens

Trigger: Calling `declared(params)` inside `before do ... end` in an endpoint or namespace. Calling `declared` from a `rescue_from` handler or a helper invoked during the filter phase, before the route action runs.

Common situations: Refactoring an endpoint and moving parameter filtering into a before block for reuse. Trying to log or whitelist params in a global before filter. Upgrading from an old Grape version where the ordering was not enforced.

Related errors

AI-assisted analysis of ruby-grape/grape@22d7975629 (2026-08-21). Data as JSON: /api/errors/3aaf6c118880958a. Report an issue: GitHub.