Fix UnknownAuthStrategy raised when custom auth strategy inherits from Grape::Middleware::Auth::Base

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Summary

Fixes #2669.

Problem

PR #2563 moved the strategy lookup in Grape::Middleware::Auth::Base#initialize from request-time to initialization-time. However, when a custom auth strategy class inherits from Grape::Middleware::Auth::Base (as documented in the README and explicitly supported via Grape::Middleware::Auth::Strategies.add), calling StrategyInfo#create instantiates that class via auth_class.new(app) — without any options. The inherited initialize then tries to look up options[:type] which is nil, causing:

Grape::Exceptions::UnknownAuthStrategy: unknown auth strategy:

(Note the blank strategy name — because options[:type] is nil.)

Fix

Guard the strategy lookup so it only runs when :type is present in options. This preserves compile-time validation for the outer Grape::Middleware::Auth::Base middleware wrapper while allowing subclasses to be instantiated cleanly as the actual strategy implementations.

def initialize(app, **options)
  super
  return unless options.key?(:type)

  @auth_strategy = Grape::Middleware::Auth::Strategies[options[:type]].tap do |auth_strategy|
    raise Grape::Exceptions::UnknownAuthStrategy.new(strategy: options[:type]) unless auth_strategy
  end
end

Test

Added a spec that registers a custom auth middleware class inheriting from Grape::Middleware::Auth::Base and verifies it works correctly with auth :custom_token in an API.

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Danger Report

No issues found.

View run

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Needs #2670.