Add equality to ALL THE THINGS (that matter)

People are often trying to use ARel nodes inside ActiveRecord, and when
they do so, lots of things can break, because ActiveRecord relies on
Array#uniq and sometimes hash key equality to handle values that end up
in wheres, havings, etc. By implementing equality for all the nodes, we
should hopefully be able to prevent any nodes (even nodes containing
other nodes) from failing an equality check they should otherwise pass,
and alleviate many of these errors.

Fixes #130

1 files changed, 22 insertions, 2 deletions

diff --git a/test/nodes/test_table_alias.rb b/test/nodes/test_table_alias.rb
index fef24bb19e..4aafd12b79 100644
--- a/test/nodes/test_table_alias.rb
+++ b/test/nodes/test_table_alias.rb
@@ -5,12 +5,32 @@ module Arel
   module Nodes
     describe 'table alias' do
       it 'has an #engine which delegates to the relation' do
-        engine   = Object.new
-        relation = OpenStruct.new(:engine => engine)
+        engine   = 'vroom'
+        relation = Table.new(:users, engine)
 
         node = TableAlias.new relation, :foo
         node.engine.must_equal engine
       end
+
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          relation1 = Table.new(:users, 'vroom')
+          node1     = TableAlias.new relation1, :foo
+          relation2 = Table.new(:users, 'vroom')
+          node2     = TableAlias.new relation2, :foo
+          array = [node1, node2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          relation1 = Table.new(:users, 'vroom')
+          node1     = TableAlias.new relation1, :foo
+          relation2 = Table.new(:users, 'vroom')
+          node2     = TableAlias.new relation2, :bar
+          array = [node1, node2]
+          assert_equal 2, array.uniq.size
+        end
+      end
     end
   end
 end