Use ActiveSupport::Callbacks

Author: javierav

.rubocop.yml

@@ -38,6 +38,10 @@ Metrics/ModuleLength:
     - hash
     - heredoc
 
+Naming/FileName:
+  Exclude:
+    - "**/lib/pundit-before.rb"
+
 Style/Documentation:
   Enabled: false
 

CHANGELOG.md

@@ -1,4 +1,4 @@
 ## [Unreleased]
 
-## [0.0.1] - 2023-01-03
+## [0.0.1] - 2023-01-15
 - Initial release

README.md

@@ -2,14 +2,15 @@
 
 ![CI](https://github.com/javierav/pundit-before/workflows/CI/badge.svg)
 
-Add before hook to pundit
+Adds `before` hook to pundit policy classes to resolve things like varvet/pundit#474. Inspired by action_policy
+[pre-checks](https://actionpolicy.evilmartians.io/#/pre_checks).
 
 ## Installation
 
 Add this line to your application's Gemfile:
 
 ```ruby
-gem 'pundit-before'
+gem "pundit-before"
 ```
 
 And then execute:
@@ -20,6 +21,173 @@ bundle install
 
 ## Usage
 
+Use `allow!` inside callback method or block to return `true` without evaluating `edit?` method defined in policy.
+
+```ruby
+class UserPolicy < ApplicationPolicy
+  include Pundit::Before
+
+  before :check_admin
+
+  def edit?
+    false
+  end
+
+  private
+
+  def check_admin
+    allow! if user.admin?
+  end
+end
+
+UserPolicy.new(User.new(admin: true), record).edit?  # => true
+UserPolicy.new(User.new(admin: false), record).edit? # => false
+```
+
+Use `deny!` inside callback method or block to return `false` without evaluating `edit?` method defined in policy.
+
+```ruby
+class UserPolicy < ApplicationPolicy
+  include Pundit::Before
+
+  before :check_admin
+
+  def edit?
+    true
+  end
+
+  private
+
+  def check_admin
+    deny! unless user.admin?
+  end
+end
+
+UserPolicy.new(User.new(admin: true), record).edit?  # => true
+UserPolicy.new(User.new(admin: false), record).edit? # => false
+```
+
+Internally `before` hook is implemented as `ActiveSupport::Callbacks`, so the callback chain will halt if do any call to
+`allow!` or `deny!` method. It's similar as Rails controller action filters works.
+
+### block form
+
+```ruby
+class UserPolicy < ApplicationPolicy
+  include Pundit::Before
+
+  before do
+    allow! if user.admin?
+  end
+
+  def edit?
+    false
+  end
+end
+```
+
+### skip before hook
+
+```ruby
+class UserPolicy < ApplicationPolicy
+  include Pundit::Before
+
+  before :check_admin
+
+  def edit?
+    false
+  end
+
+  private
+
+  def check_admin
+    allow! if user.admin?
+  end
+end
+
+class OperatorPolicy < UserPolicy
+  skip_before :check_admin
+end
+
+UserPolicy.new(User.new(admin: true), record).edit?     # => true
+OperatorPolicy.new(User.new(admin: true), record).edit? # => false
+```
+
+### using `only` modifier
+
+```ruby
+class UserPolicy < ApplicationPolicy
+  include Pundit::Before
+
+  before :check_admin, only: :update?
+
+  def edit?
+    false
+  end
+
+  private
+
+  def check_admin
+    allow! if user.admin?
+  end
+end
+
+UserPolicy.new(User.new(admin: true), record).edit? # => false
+```
+
+### using `except` modifier
+
+```ruby
+class UserPolicy < ApplicationPolicy
+  include Pundit::Before
+
+  before :check_admin, except: :edit?
+
+  def edit?
+    false
+  end
+
+  def destroy?
+    false
+  end
+
+  private
+
+  def check_admin
+    allow! if user.admin?
+  end
+end
+
+UserPolicy.new(User.new(admin: true), record).edit?    # => false
+UserPolicy.new(User.new(admin: true), record).destroy? # => true
+```
+
+### calling multiple methods
+
+```ruby
+class UserPolicy < BasePolicy
+  before :check_presence, :check_admin
+
+  def edit?
+    false
+  end
+
+  private
+
+  def check_presence
+    deny! unless user.present?
+  end
+
+  def check_admin
+    allow! if user.admin?
+  end
+end
+
+UserPolicy.new(nil, record).edit?                    # => false
+UserPolicy.new(User.new(admin: false), record).edit? # => false
+UserPolicy.new(User.new(admin: true), record).edit?  # => true
+```
+
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests.

lib/pundit-before.rb

@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require "pundit/before"

lib/pundit/before.rb

@@ -1,60 +1,98 @@
 # frozen_string_literal: true
 
-require "active_support/concern"
-require "active_support/core_ext/class/attribute"
+require "active_support/callbacks"
+require "active_support/core_ext/array/wrap"
 require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/object/blank"
 
 require_relative "before/version"
 
 module Pundit
   module Before
-    # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/MethodLength
+    # rubocop:disable Metrics/MethodLength
     def self.included(base)
       base.extend ClassMethods
+      base.include ActiveSupport::Callbacks
 
       base.class_eval do
-        class_attribute :_pundit_before, default: []
+        define_callbacks :_pundit_before, skip_after_callbacks_if_terminated: true
 
         def self.method_added(method_name)
           super
 
-          return if @_pundit_before_running
           return unless method_name.to_s =~ /.*\?$/ && public_method_defined?(method_name)
+          return if @_pundit_before_running
 
           @_pundit_before_running = true
 
           old_method = instance_method(method_name)
 
           redefine_method(method_name) do
-            result = catch :halt do
-              (_pundit_before.presence || []).each do |name, block|
-                name.present? ? send(name) : instance_eval(&block)
-              end
-              nil
-            end
-
-            result.nil? ? old_method.bind(self).call : result
+            @_pundit_before_result = nil
+            @_pundit_before_method = method_name
+
+            run_callbacks :_pundit_before
+
+            @_pundit_before_result.nil? ? old_method.bind(self).call : @_pundit_before_result
           end
 
           @_pundit_before_running = false
         end
       end
     end
-    # rubocop:enable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/MethodLength
+    # rubocop:enable Metrics/MethodLength
+
+    class CallbackFilter
+      def initialize(methods)
+        @methods = Array(methods).map(&:to_sym)
+      end
+
+      def match?(object)
+        @methods.include?(object.instance_variable_get(:@_pundit_before_method).to_sym)
+      end
+
+      alias after  match?
+      alias before match?
+      alias around match?
+    end
 
     module ClassMethods
-      def before(method_name=nil, &block)
-        self._pundit_before = _pundit_before.dup.push([method_name, block])
+      def before(*method_names, **options, &block)
+        _normalize_callback_options(options)
+
+        if block_given?
+          set_callback :_pundit_before, :before, **options, &block
+        else
+          set_callback :_pundit_before, :before, *method_names, **options
+        end
+      end
+
+      def skip_before(*method_names, **options)
+        _normalize_callback_options(options)
+        skip_callback :_pundit_before, :before, *method_names, **options
+      end
+
+      def _normalize_callback_options(options)
+        _normalize_callback_option(options, :only, :if)
+        _normalize_callback_option(options, :except, :unless)
+      end
+
+      def _normalize_callback_option(options, from, to)
+        return unless (from = options.delete(from))
+
+        from = CallbackFilter.new(from)
+        options[to] = Array(options[to]).unshift(from)
       end
     end
 
     def allow!
-      throw :halt, true
+      @_pundit_before_result = true
+      throw :abort
     end
 
     def deny!
-      throw :halt, false
+      @_pundit_before_result = false
+      throw :abort
     end
   end
 end

pundit-before.gemspec

@@ -8,7 +8,7 @@ Gem::Specification.new do |spec|
   #
   spec.name = "pundit-before"
   spec.version = Pundit::Before.version
-  spec.summary = "Add before hook to pundit"
+  spec.summary = "Adds before hook to pundit policy classes"
   spec.homepage = "https://github.com/javierav/pundit-before"
   spec.license = "MIT"
 

test/test_block.rb

@@ -3,31 +3,27 @@
 require "test_helper"
 
 class TestBlock < Minitest::Test
-  def test_not_admin_and_not_owner
-    user = User.new(2)
-    record = Record.new(1, 3)
-
-    refute_predicate BeforeWithBlockPolicy.new(user, record), :edit?
+  class BlockPolicy < BasePolicy
+    before do
+      deny! unless user.admin?
+    end
+
+    def edit?
+      true
+    end
   end
 
-  def test_not_admin_and_owner
-    user = User.new(3)
-    record = Record.new(1, 3)
-
-    refute_predicate BeforeWithBlockPolicy.new(user, record), :edit?
-  end
-
-  def test_admin_and_not_owner
+  def test_admin
     user = User.new(1)
-    record = Record.new(1, 2)
+    policy = BlockPolicy.new(user)
 
-    refute_predicate BeforeWithBlockPolicy.new(user, record), :edit?
+    assert_predicate policy, :edit?
   end
 
-  def test_admin_and_owner
-    user = User.new(1)
-    record = Record.new(1, 1)
+  def test_user
+    user = User.new(2)
+    policy = BlockPolicy.new(user)
 
-    assert_predicate BeforeWithBlockPolicy.new(user, record), :edit?
+    refute_predicate policy, :edit?
   end
 end