Module: Grape::Util::ShadowedRescueHandlers

Defined in:
lib/grape/util/shadowed_rescue_handlers.rb

Overview

Diagnostics for rescue_from registrations that can never run.

Middleware::Error resolves with find, so within a scope the first matching class wins and one registered for a class an earlier handler already covers is dead code — silently, before this warned:

rescue_from StandardError do ... end   # wins
rescue_from ArgumentError do ... end   # never runs

Warn rather than reorder: which should win is the author's call, and rescue_from :all (consulted only after the registered handlers) already offers "broad first, specific still wins" to anyone who wants it.

Class Method Summary collapse

Class Method Details

.message_for(klass, covered_by) ⇒ Object 



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# File 'lib/grape/util/shadowed_rescue_handlers.rb', line 41

def message_for(klass, covered_by)
  return "Grape: rescue_from #{klass} was already registered in this scope; the first handler is kept and this one will never run." if klass == covered_by

  "Grape: rescue_from #{klass} will never run — #{covered_by} was registered earlier in the same scope " \
    'and is matched first. Register the more specific class before the broader one.'
end

.warn_about(registered, mapping) ⇒ void

This method returns an undefined value.

Only a scope's own registrations are compared: across scopes the nearest one deliberately wins, so an inner rescue_from StandardError shadowing an outer rescue_from ArgumentError is the documented behaviour rather than a mistake. Classes sharing a handler object are skipped too, since rescue_from A, B registers one handler for both and the entry that loses to the other changes nothing.

Parameters:

  • registered (Hash) —

    the scope's own handlers, in registration order

  • mapping (Hash) —

    the handlers being registered now



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# File 'lib/grape/util/shadowed_rescue_handlers.rb', line 30

def warn_about(registered, mapping)
  return if registered.empty?

  mapping.each do |klass, handler|
    covered_by, = registered.find { |already, existing| klass <= already && !existing.equal?(handler) }
    next unless covered_by

    warn(message_for(klass, covered_by))
  end
end