Implement initial support for the Squeel adapter.

cancancan-squeel.gemspec

@@ -20,9 +20,15 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_development_dependency 'bundler', '~> 1.11'
-  spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rake'
   spec.add_development_dependency 'rspec', '~> 3.0'
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'coveralls'
   spec.add_development_dependency 'codeclimate-test-reporter'
+
+  spec.add_development_dependency 'sqlite3'
+
+  spec.add_dependency 'activerecord', '>= 4.1'
+  spec.add_dependency 'cancancan', '~> 1.10'
+  spec.add_dependency 'squeel', '~> 1.2'
 end

lib/cancancan/squeel.rb

@@ -1,5 +1,8 @@
+require 'active_record'
+require 'cancancan'
+require 'squeel'
+
 require 'cancancan/squeel/version'
+require 'cancancan/squeel/active_record_disabler'
+require 'cancancan/squeel/squeel_adapter'
 
-module CanCanCan::Squeel
-  # Your code goes here...
-end

lib/cancancan/squeel/active_record_disabler.rb

@@ -0,0 +1,7 @@
+class CanCanCan::Squeel::ActiveRecordDisabler
+  ::CanCan::ModelAdapters::ActiveRecord4Adapter.class_eval do
+    def self.for_class?(_)
+      false
+    end
+  end
+end

lib/cancancan/squeel/squeel_adapter.rb

@@ -0,0 +1,195 @@
+class CanCanCan::Squeel::SqueelAdapter < CanCan::ModelAdapters::AbstractAdapter
+  def self.for_class?(model_class)
+    model_class <= ActiveRecord::Base
+  end
+
+  def self.override_condition_matching?(subject, name, _)
+    return false unless subject.class.respond_to?(:defined_enums)
+
+    subject.class.defined_enums.include?(name.to_s)
+  end
+
+  def self.matches_condition?(subject, name, value)
+    # Get the mapping from enum strings to values.
+    enum = subject.class.public_send(name.to_s.pluralize)
+
+    # Get the value of the attribute as an integer.
+    attribute = enum[subject.public_send(name)]
+
+    # Check to see if the value matches the condition.
+    value.is_a?(Enumerable) ? value.include?(attribute) : attribute == value
+  end
+
+  def database_records
+    # TODO: Handle overridden scopes.
+    relation.distinct
+  end
+
+  private
+
+  # Builds a relation that expresses the set of provided rules.
+  #
+  # This first joins all the tables specified in the rules, then builds the corresponding Squeel
+  # expression for the conditions.
+  def relation
+    join_scope = @rules.reduce(@model_class.where(nil)) do |scope, rule|
+      add_joins_to_scope(scope, build_join_list(rule.conditions))
+    end
+
+    add_conditions_to_scope(join_scope)
+  end
+
+  # Builds an array of joins for the given conditions hash.
+  #
+  # For example:
+  #
+  # a: { b: { c: 3 }, d: { e: 4 }} => [[:a, :b], [:a, :d]]
+  #
+  # @param [Hash] conditions The conditions to build the joins.
+  # @return [Array<Array<Symbol>>] The joins needed to satisfy the given conditions
+  def build_join_list(conditions)
+    conditions.flat_map do |key, value|
+      if value.is_a?(Hash)
+        [[key]].concat(build_join_list(value).map { |join| Array(join).unshift(key) })
+      else
+        []
+      end
+    end
+  end
+
+  # Builds a relation, outer joined on the provided associations.
+  #
+  # @param [ActiveRecord::Relation] scope The current scope to add the joins to.
+  # @param [Array<Array<Symbol>>] joins The set of associations to outer join with.
+  # @return [ActiveRecord::Relation] The built relation.
+  def add_joins_to_scope(scope, joins)
+    joins.reduce(scope) do |result, join|
+      result.joins do
+        join.reduce(self) do |relation, association|
+          relation.__send__(association).outer
+        end
+      end
+    end
+  end
+
+  # Adds the rule conditions to the scope.
+  #
+  # This builds Squeel expression for each rule, and combines the expression with those to the left
+  # using a fold-left.
+  #
+  # @param [ActiveRecord::Relation] scope The scope to add the rule conditions to.
+  def add_conditions_to_scope(scope)
+    adapter = self
+    rules = @rules
+
+    # default n
+    scope.where do
+      rules.reduce(nil) do |left_expression, rule|
+        combined_rule = adapter.send(:combine_expression_with_rule, self, left_expression, rule)
+        break if combined_rule.nil?
+
+        combined_rule
+      end
+    end
+  end
+
+  # Combines the given expression with the new rule.
+  #
+  # @param squeel The Squeel scope.
+  # @param left_expression The Squeel expression for all preceding rules.
+  # @param [CanCan::Rule] rule The rule being added.
+  # @return [Squeel::Nodes::Node] If the rule has an expression.
+  # @return [NilClass] If the rule is unconditional.
+  def combine_expression_with_rule(squeel, left_expression, rule)
+    right_expression = build_expression_from_rule(squeel, rule)
+    return right_expression if right_expression.nil? || !left_expression
+
+    if rule.base_behavior
+      left_expression | right_expression
+    else
+      left_expression & right_expression
+    end
+  end
+
+  # Builds a Squeel expression representing the rule's conditions.
+  #
+  # @param squeel The Squeel scope.
+  # @param [CanCan::Rule] rule The rule being built.
+  def build_expression_from_rule(squeel, rule)
+    comparator = rule.base_behavior ? :== : :!=
+    build_expression_node(squeel, @model_class, comparator, rule.conditions, true)
+  end
+
+  # Builds a new Squeel expression node.
+  #
+  # @param node The parent node context.
+  # @param [Class] model_class The model class which the conditions reference.
+  # @param [Symbol] comparator The comparator to use when generating the comparison.
+  # @param [Hash] conditions The values to compare the given node's attributes against.
+  # @param [Boolean] root True if the node being built is from the root. The root node is special
+  #   because it does not mutate itself; all other nodes do.
+  def build_expression_node(node, model_class, comparator, conditions, root = false)
+    conditions.reduce(nil) do |left_expression, (key, value)|
+      comparison_node = build_comparison_node(root ? node : node.dup, model_class, key,
+                                              comparator, value)
+      if left_expression
+        left_expression & comparison_node
+      else
+        comparison_node
+      end
+    end
+  end
+
+  # Builds a comparison node for the given key and value.
+  #
+  # @param node The node context to build the comparison.
+  # @param [Class] model_class The model class which the conditions reference.
+  # @param [Symbol] key The column to compare against.
+  # @param [Symbol] comparator The comparator to compare the column against the value.
+  # @param value The value to compare the column against.
+  def build_comparison_node(node, model_class, key, comparator, value)
+    if value.is_a?(Hash)
+      reflection = model_class.reflect_on_association(key)
+      build_expression_node(node.__send__(key), reflection.klass, comparator, value)
+    else
+      key, comparator, value = squeel_comparison_for(model_class, key, comparator, value)
+      node.__send__(key).public_send(comparator, value)
+    end
+  end
+
+  # Picks the appropriate column, comparator, and value to use in the Squeel expression.
+  #
+  # This checks for association references: this will use the appropriate column name.
+  #
+  # Array values are interpreted as alternative choices allowed or disallowed.
+  #
+  # @param [Class] model_class The model class which the key references.
+  # @param [Symbol] key The column being compared.
+  # @param [Symbol] comparator The comparator to get the appropriate Squeel comparator for.
+  # @param value The value to be comparing against.
+  # @return [Array<(Symbol, Symbol, Object)>] A triple containing the column to compare with, the
+  #   comparator to use, and the value to compare with.
+  def squeel_comparison_for(model_class, key, comparator, value)
+    if (association = model_class.reflect_on_association(key))
+      key = association.foreign_key
+    end
+
+    comparator = squeel_comparator_for(comparator, value)
+    [key, comparator, value]
+  end
+
+  # Maps the given comparator to a comparator appropriate for the given value.
+  #
+  # Array values are interpreted as alternative choices allowed or disallowed.
+  #
+  # @param [Symbol] comparator The comparator to get the appropriate Squeel comparator for.
+  # @param value The value to be comparing against.
+  # @return [Symbol] The comparator for the desired effect, suitable for the given type.
+  def squeel_comparator_for(comparator, value)
+    case [comparator, value]
+    when :==, Array then :>>
+    when :!=, Array then :<<
+    else comparator
+    end
+  end
+end

spec/cancancan/squeel_spec.rb

@@ -5,7 +5,72 @@
     expect(CanCanCan::Squeel::VERSION).not_to be nil
   end
 
-  it 'does something useful' do
-    expect(false).to eq(true)
+  let(:ability) { double.extend(CanCan::Ability) }
+
+  with_database(:sqlite) do
+    it 'respects scope on included associations' do
+      ability.can :read, [Parent, Child]
+
+      parent = Parent.create!
+      child1 = Child.create!(parent: parent, created_at: 1.hours.ago)
+      child2 = Child.create!(parent: parent, created_at: 2.hours.ago)
+
+      parents = Parent.accessible_by(ability).order(created_at: :asc).includes(:children)
+      expect(parents.first.children).to eq([child2, child1])
+    end
+
+    it 'supports repeated tables in deeply nested conditions' do
+      parent1 = Parent.create!
+      parent2 = Parent.create!
+      ability.can :read, Parent, children: {
+        other_parent: {
+          id: parent1.id
+        }
+      }
+
+      # check that we are not directly accessible
+      expect(Parent.accessible_by(ability)).to be_empty
+
+      _child = Child.create!(parent: parent2, other_parent: parent1)
+      expect(Parent.accessible_by(ability)).to contain_exactly(parent2)
+    end
+
+    it 'allows using accessible_by on a chained scope' do
+      parent1 = Parent.create!
+      parent2 = Parent.create!
+      parent3 = Parent.create!
+      _child1 = Child.create!(parent: parent1, other_parent: parent2)
+      _child2 = Child.create!(parent: parent2, other_parent: parent3)
+      ability.can :read, Parent, other_parents: { id: parent3.id }
+
+      expect(parent1.other_parents.accessible_by(ability)).to contain_exactly(parent2)
+    end
+
+    it 'allows filters on enums' do
+      red = Shape.create!(color: :red)
+      green = Shape.create!(color: :green)
+      blue = Shape.create!(color: :blue)
+
+      # A condition with a single value.
+      ability.can(:read, Shape, color: Shape.colors[:green])
+
+      expect(ability.cannot?(:read, red)).to be true
+      expect(ability.can?(:read, green)).to be true
+      expect(ability.cannot?(:read, blue)).to be true
+
+      accessible = Shape.accessible_by(ability)
+      expect(accessible).to contain_exactly(green)
+
+      # A condition with multiple values.
+      ability.can(:update, Shape, color: [Shape.colors[:red],
+                                          Shape.colors[:blue]])
+
+      expect(ability.can?(:update, red)).to be true
+      expect(ability.cannot?(:update, green)).to be true
+      expect(ability.can?(:update, blue)).to be true
+
+      accessible = Shape.accessible_by(ability, :update)
+      expect(accessible).to contain_exactly(red, blue)
+    end
   end
 end

spec/spec_helper.rb

@@ -19,6 +19,7 @@
 $LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
 require 'coverage_helper'
 require 'cancancan/squeel'
+Dir["#{__dir__}/support/*.rb"].each { |f| require f }
 
 RSpec.configure do |config|
   # rspec-expectations config goes here. You can use an alternate