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108 lines
4 KiB
Ruby
108 lines
4 KiB
Ruby
module ActiveSupport
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# Rescuable module adds support for easier exception handling.
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module Rescuable
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def self.included(base) # :nodoc:
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base.class_inheritable_accessor :rescue_handlers
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base.rescue_handlers = []
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base.extend(ClassMethods)
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end
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module ClassMethods
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# Rescue exceptions raised in controller actions.
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#
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# <tt>rescue_from</tt> receives a series of exception classes or class
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# names, and a trailing <tt>:with</tt> option with the name of a method
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# or a Proc object to be called to handle them. Alternatively a block can
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# be given.
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#
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# Handlers that take one argument will be called with the exception, so
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# that the exception can be inspected when dealing with it.
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#
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# Handlers are inherited. They are searched from right to left, from
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# bottom to top, and up the hierarchy. The handler of the first class for
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# which <tt>exception.is_a?(klass)</tt> holds true is the one invoked, if
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# any.
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#
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# class ApplicationController < ActionController::Base
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# rescue_from User::NotAuthorized, :with => :deny_access # self defined exception
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# rescue_from ActiveRecord::RecordInvalid, :with => :show_errors
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#
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# rescue_from 'MyAppError::Base' do |exception|
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# render :xml => exception, :status => 500
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# end
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#
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# protected
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# def deny_access
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# ...
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# end
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#
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# def show_errors(exception)
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# exception.record.new_record? ? ...
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# end
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# end
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def rescue_from(*klasses, &block)
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options = klasses.extract_options!
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unless options.has_key?(:with)
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if block_given?
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options[:with] = block
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else
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raise ArgumentError, "Need a handler. Supply an options hash that has a :with key as the last argument."
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end
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end
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klasses.each do |klass|
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key = if klass.is_a?(Class) && klass <= Exception
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klass.name
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elsif klass.is_a?(String)
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klass
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else
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raise ArgumentError, "#{klass} is neither an Exception nor a String"
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end
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# put the new handler at the end because the list is read in reverse
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rescue_handlers << [key, options[:with]]
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end
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end
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end
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# Tries to rescue the exception by looking up and calling a registered handler.
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def rescue_with_handler(exception)
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if handler = handler_for_rescue(exception)
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handler.arity != 0 ? handler.call(exception) : handler.call
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true # don't rely on the return value of the handler
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end
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end
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def handler_for_rescue(exception)
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# We go from right to left because pairs are pushed onto rescue_handlers
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# as rescue_from declarations are found.
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_, rescuer = Array(rescue_handlers).reverse.detect do |klass_name, handler|
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# The purpose of allowing strings in rescue_from is to support the
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# declaration of handler associations for exception classes whose
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# definition is yet unknown.
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#
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# Since this loop needs the constants it would be inconsistent to
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# assume they should exist at this point. An early raised exception
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# could trigger some other handler and the array could include
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# precisely a string whose corresponding constant has not yet been
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# seen. This is why we are tolerant to unknown constants.
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#
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# Note that this tolerance only matters if the exception was given as
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# a string, otherwise a NameError will be raised by the interpreter
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# itself when rescue_from CONSTANT is executed.
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klass = self.class.const_get(klass_name) rescue nil
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klass ||= klass_name.constantize rescue nil
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exception.is_a?(klass) if klass
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end
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case rescuer
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when Symbol
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method(rescuer)
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when Proc
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rescuer.bind(self)
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end
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end
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end
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end
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