Add missing hash, eql?, == to various node classes

Some of the nodes classes are missing either one or many of the common comparison methods #hash, #eql? and #==.

This makes comparision and working with the ast sometimes painful, as equality or operations likes array differences (which uses a hash behind the scene) produces unexpected results.

A test has been added that ensures that every descendants of Node:
* have all 3 methods
* that all 3 methods were defined from the same class
* that the class defining all 3 is also a descendant of Node, to avoid the default ones that rely on identity only

7 files changed, 22 insertions, 1 deletions

diff --git a/lib/arel/nodes/bind_param.rb b/lib/arel/nodes/bind_param.rb
index 225fcc4798..efa4f452d4 100644
--- a/lib/arel/nodes/bind_param.rb
+++ b/lib/arel/nodes/bind_param.rb
@@ -9,10 +9,15 @@ module Arel
         super()
       end
 
-      def ==(other)
+      def hash
+        [self.class, self.value].hash
+      end
+
+      def eql?(other)
         other.is_a?(BindParam) &&
           value == other.value
       end
+      alias :== :eql?
 
       def nil?
         value.nil?
diff --git a/lib/arel/nodes/false.rb b/lib/arel/nodes/false.rb
index 26b4e5db97..fb821dd522 100644
--- a/lib/arel/nodes/false.rb
+++ b/lib/arel/nodes/false.rb
@@ -9,6 +9,7 @@ module Arel
       def eql? other
         self.class == other.class
       end
+      alias :== :eql?
     end
   end
 end
diff --git a/lib/arel/nodes/function.rb b/lib/arel/nodes/function.rb
index 28a394e9f3..b2b89ee9ff 100644
--- a/lib/arel/nodes/function.rb
+++ b/lib/arel/nodes/function.rb
@@ -29,6 +29,8 @@ module Arel
           self.alias == other.alias &&
           self.distinct == other.distinct
       end
+      alias :== :eql?
+
     end
 
     %w{
diff --git a/lib/arel/nodes/terminal.rb b/lib/arel/nodes/terminal.rb
index 6f60fe006f..421f039904 100644
--- a/lib/arel/nodes/terminal.rb
+++ b/lib/arel/nodes/terminal.rb
@@ -9,6 +9,7 @@ module Arel
       def eql? other
         self.class == other.class
       end
+      alias :== :eql?
     end
   end
 end
diff --git a/lib/arel/nodes/true.rb b/lib/arel/nodes/true.rb
index 796b5b9348..bb9d8c1414 100644
--- a/lib/arel/nodes/true.rb
+++ b/lib/arel/nodes/true.rb
@@ -9,6 +9,7 @@ module Arel
       def eql? other
         self.class == other.class
       end
+      alias :== :eql?
     end
   end
 end
diff --git a/lib/arel/nodes/values_list.rb b/lib/arel/nodes/values_list.rb
index b39aaa1465..89cea1790d 100644
--- a/lib/arel/nodes/values_list.rb
+++ b/lib/arel/nodes/values_list.rb
@@ -8,6 +8,16 @@ module Arel
         @rows = rows
         super()
       end
+
+      def hash
+        @rows.hash
+      end
+
+      def eql? other
+        self.class == other.class &&
+          self.rows == other.rows
+      end
+      alias :== :eql?
     end
   end
 end
diff --git a/lib/arel/nodes/window.rb b/lib/arel/nodes/window.rb
index 535c0c6238..23a005daba 100644
--- a/lib/arel/nodes/window.rb
+++ b/lib/arel/nodes/window.rb
@@ -107,6 +107,7 @@ module Arel
       def eql? other
         self.class == other.class
       end
+      alias :== :eql?
     end
 
     class Preceding < Unary