Active Record: fix `size` method for grouped relations

lib/will_paginate/active_record.rb

@@ -73,7 +73,7 @@ def count
 
       # workaround for Active Record 3.0
       def size
-        if !loaded? and limit_value
+        if !loaded? and limit_value and group_values.empty?
           [super, limit_value].min
         else
           super
@@ -83,12 +83,9 @@ def size
       # overloaded to be pagination-aware
       def empty?
         if !loaded? and offset_value
-          rel_count = count
-          if rel_count.respond_to?(:size) and !rel_count.is_a?(Integer)
-            rel_count.size <= offset_value
-          else
-            rel_count <= offset_value
-          end
+          result = count
+          result = result.size if result.respond_to?(:size) and !result.is_a?(Integer)
+          result <= offset_value
         else
           super
         end

spec/finders/active_record_spec.rb

@@ -146,6 +146,13 @@
       }.should run_queries(1)
     end
 
+    it "supports `size` for grouped queries" do
+      topics = Topic.group(:project_id).paginate :page => 1, :per_page => 3
+      lambda {
+        topics.size.should == {nil=>2, 1=>2}
+      }.should run_queries(1)
+    end
+
     it "overrides total_entries count with a fixed value" do
       lambda {
         topics = Topic.paginate :page => 1, :per_page => 3, :total_entries => 999