Extract module and tests from rails

README

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+This module provides a class-level method for specifying that certain
+actions are guarded against being called without certain prerequisites
+being met. This is essentially a special kind of before_filter.
+
+An action may be guarded against being invoked without certain request
+parameters being set, or without certain session values existing.
+
+When a verification is violated, values may be inserted into the flash, and
+a specified redirection is triggered. If no specific action is configured,
+verification failures will by default result in a 400 Bad Request response.
+
+Usage:
+
+  class GlobalController < ActionController::Base
+    # Prevent the #update_settings action from being invoked unless
+    # the 'admin_privileges' request parameter exists. The
+    # settings action will be redirected to in current controller
+    # if verification fails.
+    verify :params => "admin_privileges", :only => :update_post,
+           :redirect_to => { :action => "settings" }
+
+    # Disallow a post from being updated if there was no information
+    # submitted with the post, and if there is no active post in the
+    # session, and if there is no "note" key in the flash. The route
+    # named category_url will be redirected to if verification fails.
+
+    verify :params => "post", :session => "post", "flash" => "note",
+           :only => :update_post,
+           :add_flash => { "alert" => "Failed to create your message" },
+           :redirect_to => :category_url
+
+Note that these prerequisites are not business rules. They do not examine
+the content of the session or the parameters. That level of validation should
+be encapsulated by your domain model or helper methods in the controller.

Rakefile

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+require 'rake'
+require 'rake/testtask'
+require 'rake/rdoctask'
+
+desc 'Default: run unit tests.'
+task :default => :test
+
+desc 'Test the verification plugin.'
+Rake::TestTask.new(:test) do |t|
+  t.libs << 'lib'
+  t.pattern = 'test/**/*_test.rb'
+  t.verbose = true
+end
+
+desc 'Generate documentation for the verification plugin.'
+Rake::RDocTask.new(:rdoc) do |rdoc|
+  rdoc.rdoc_dir = 'rdoc'
+  rdoc.title    = 'Verification'
+  rdoc.options << '--line-numbers' << '--inline-source'
+  rdoc.rdoc_files.include('README')
+  rdoc.rdoc_files.include('lib/**/*.rb')
+end

init.rb

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+require 'action_controller/verification'

lib/action_controller/verification.rb

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+module ActionController #:nodoc:
+  module Verification #:nodoc:
+    extend ActiveSupport::Concern
+
+    include AbstractController::Callbacks, Flash, Rendering
+
+    # This module provides a class-level method for specifying that certain
+    # actions are guarded against being called without certain prerequisites
+    # being met. This is essentially a special kind of before_filter.
+    #
+    # An action may be guarded against being invoked without certain request
+    # parameters being set, or without certain session values existing.
+    #
+    # When a verification is violated, values may be inserted into the flash, and
+    # a specified redirection is triggered. If no specific action is configured,
+    # verification failures will by default result in a 400 Bad Request response.
+    #
+    # Usage:
+    #
+    #   class GlobalController < ActionController::Base
+    #     # Prevent the #update_settings action from being invoked unless
+    #     # the 'admin_privileges' request parameter exists. The
+    #     # settings action will be redirected to in current controller
+    #     # if verification fails.
+    #     verify :params => "admin_privileges", :only => :update_post,
+    #            :redirect_to => { :action => "settings" }
+    #
+    #     # Disallow a post from being updated if there was no information
+    #     # submitted with the post, and if there is no active post in the
+    #     # session, and if there is no "note" key in the flash. The route
+    #     # named category_url will be redirected to if verification fails.
+    #
+    #     verify :params => "post", :session => "post", "flash" => "note",
+    #            :only => :update_post,
+    #            :add_flash => { "alert" => "Failed to create your message" },
+    #            :redirect_to => :category_url
+    #
+    # Note that these prerequisites are not business rules. They do not examine
+    # the content of the session or the parameters. That level of validation should
+    # be encapsulated by your domain model or helper methods in the controller.
+    module ClassMethods
+      # Verify the given actions so that if certain prerequisites are not met,
+      # the user is redirected to a different action. The +options+ parameter
+      # is a hash consisting of the following key/value pairs:
+      #
+      # <tt>:params</tt>::
+      #   a single key or an array of keys that must be in the <tt>params</tt>
+      #   hash in order for the action(s) to be safely called.
+      # <tt>:session</tt>::
+      #   a single key or an array of keys that must be in the <tt>session</tt>
+      #   in order for the action(s) to be safely called.
+      # <tt>:flash</tt>::
+      #   a single key or an array of keys that must be in the flash in order
+      #   for the action(s) to be safely called.
+      # <tt>:method</tt>::
+      #   a single key or an array of keys--any one of which must match the
+      #   current request method in order for the action(s) to be safely called.
+      #   (The key should be a symbol: <tt>:get</tt> or <tt>:post</tt>, for
+      #   example.)
+      # <tt>:xhr</tt>::
+      #   true/false option to ensure that the request is coming from an Ajax
+      #   call or not.
+      # <tt>:add_flash</tt>::
+      #   a hash of name/value pairs that should be merged into the session's
+      #   flash if the prerequisites cannot be satisfied.
+      # <tt>:add_headers</tt>::
+      #   a hash of name/value pairs that should be merged into the response's
+      #   headers hash if the prerequisites cannot be satisfied.
+      # <tt>:redirect_to</tt>::
+      #   the redirection parameters to be used when redirecting if the
+      #   prerequisites cannot be satisfied. You can redirect either to named
+      #   route or to the action in some controller.
+      # <tt>:render</tt>::
+      #   the render parameters to be used when the prerequisites cannot be satisfied.
+      # <tt>:only</tt>::
+      #   only apply this verification to the actions specified in the associated
+      #   array (may also be a single value).
+      # <tt>:except</tt>::
+      #   do not apply this verification to the actions specified in the associated
+      #   array (may also be a single value).
+      def verify(options={})
+        before_filter :only => options[:only], :except => options[:except] do
+          verify_action options
+        end
+      end
+    end
+
+  private
+
+    def verify_action(options) #:nodoc:
+      if prereqs_invalid?(options)
+        flash.update(options[:add_flash])              if options[:add_flash]
+        response.headers.merge!(options[:add_headers]) if options[:add_headers]
+        apply_remaining_actions(options)               unless performed?
+      end
+    end
+
+    def prereqs_invalid?(options) # :nodoc:
+      verify_presence_of_keys_in_hash_flash_or_params(options) ||
+      verify_method(options) ||
+      verify_request_xhr_status(options)
+    end
+
+    def verify_presence_of_keys_in_hash_flash_or_params(options) # :nodoc:
+      [*options[:params] ].find { |v| v && params[v.to_sym].nil?  } ||
+      [*options[:session]].find { |v| session[v].nil? } ||
+      [*options[:flash]  ].find { |v| flash[v].nil?   }
+    end
+
+    def verify_method(options) # :nodoc:
+      [*options[:method]].all? { |v| request.method != v.to_sym } if options[:method]
+    end
+
+    def verify_request_xhr_status(options) # :nodoc:
+      request.xhr? != options[:xhr] unless options[:xhr].nil?
+    end
+
+    def apply_redirect_to(redirect_to_option) # :nodoc:
+      (redirect_to_option.is_a?(Symbol) && redirect_to_option != :back) ? self.__send__(redirect_to_option) : redirect_to_option
+    end
+
+    def apply_remaining_actions(options) # :nodoc:
+      case
+        when options[:render]      ; render(options[:render])
+        when options[:redirect_to] ; redirect_to(apply_redirect_to(options[:redirect_to]))
+        else head(:bad_request)
+      end
+    end
+  end
+end
+
+ActionController::Base.send :include, ActionController::Verification