From 92a4ddd165793a5b5a3935341e08213183d88898 Mon Sep 17 00:00:00 2001
From: Joel Low <joel@joelsplace.sg>
Date: Thu, 28 Apr 2016 09:13:02 +0800
Subject: [PATCH] Allow querying nested unloaded associations using a database
 query.

---
 CHANGELOG.md                           |  7 ++++
 lib/cancancan/squeel/squeel_adapter.rb | 44 ++++++++++++++++----------
 spec/cancancan/squeel_spec.rb          | 11 +++++++
 3 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8d4b0ea..4404231 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+## master
+
+### bug fixes
+
+ - Allow querying nested unloaded associations using a database query.
+   [@lowjoel](https://github.com/lowjoel)
+
 ## 0.1.3
 
 ### enhancements
diff --git a/lib/cancancan/squeel/squeel_adapter.rb b/lib/cancancan/squeel/squeel_adapter.rb
index d11f2f6..14066fa 100644
--- a/lib/cancancan/squeel/squeel_adapter.rb
+++ b/lib/cancancan/squeel/squeel_adapter.rb
@@ -52,11 +52,14 @@ def self.match_relation?(subject, name)
   def self.matches_relation?(subject, name, value)
     relation = subject.public_send(name)
     klass = subject.class.reflect_on_association(name).klass
+    join_list = nil
 
-    relation.where do
-      expression, = CanCanCan::Squeel::ExpressionBuilder.build(self, klass, :==, value)
+    scope = relation.where do
+      expression, join_list = CanCanCan::Squeel::ExpressionBuilder.build(self, klass, :==, value)
       expression
-    end.any?
+    end
+
+    add_joins_to_scope(scope, join_list, :inner).any?
   end
   private_class_method :matches_relation?
 
@@ -65,6 +68,25 @@ def database_records
     relation.distinct
   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.
+  # @param [Symbol] join_type The type of join; defaults to outer joins.
+  # @return [ActiveRecord::Relation] The built relation.
+  def self.add_joins_to_scope(scope, joins, join_type = :outer)
+    joins.reduce(scope) do |result, join|
+      result.joins do
+        join.reduce(self) do |relation, association|
+          relation = relation.__send__(association)
+          relation = relation.__send__(join_type) unless join_type == :inner
+          relation
+        end
+      end
+    end
+  end
+  private_class_method :add_joins_to_scope
+
   private
 
   # Builds a relation that expresses the set of provided rules.
@@ -82,19 +104,9 @@ def relation
     add_joins_to_scope(scope, join_list)
   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
+  # @see CanCanCan::Squeel::SqueelAdapter.add_joins_to_scope
+  def add_joins_to_scope(*args)
+    self.class.send(:add_joins_to_scope, *args)
   end
 
   # This builds Squeel expression for each rule, and combines the expression with those to the left
diff --git a/spec/cancancan/squeel_spec.rb b/spec/cancancan/squeel_spec.rb
index 85b30d7..648692d 100644
--- a/spec/cancancan/squeel_spec.rb
+++ b/spec/cancancan/squeel_spec.rb
@@ -203,5 +203,16 @@
       ability.can?(:read, parent)
       expect(parent.children).not_to be_loaded
     end
+
+    context 'when unloaded associations include joins' do
+      it 'adds the necessary joins' do
+        parent = Parent.create!
+        ability.can(:read, Parent, children: { parent: { id: 2 }})
+        expect(parent.children).to receive(:where).and_call_original
+
+        expect(ability.can?(:read, parent)).to eq(false)
+        expect(parent.children).not_to be_loaded
+      end
+    end
   end
 end