push reduction visitors to a reduction base class

this lets our old depth first and dot visitors to work normally

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/arel/visitors/reduce.rb b/lib/arel/visitors/reduce.rb
new file mode 100644
index 0000000000..9670cad27c
--- /dev/null
+++ b/lib/arel/visitors/reduce.rb
@@ -0,0 +1,25 @@
+require 'arel/visitors/visitor'
+
+module Arel
+  module Visitors
+    class Reduce < Arel::Visitors::Visitor
+      def accept object, collector
+        visit object, collector
+      end
+
+      private
+
+      def visit object, collector
+        send dispatch[object.class], object, collector
+      rescue NoMethodError => e
+        raise e if respond_to?(dispatch[object.class], true)
+        superklass = object.class.ancestors.find { |klass|
+          respond_to?(dispatch[klass], true)
+        }
+        raise(TypeError, "Cannot visit #{object.class}") unless superklass
+        dispatch[object.class] = dispatch[superklass]
+        retry
+      end
+    end
+  end
+end