Cope with scoped :select when counting.

lib/will_paginate/finder.rb

@@ -181,7 +181,19 @@ def method_missing_with_paginate(method, *args, &block) #:nodoc:
       # in the database. It relies on the ActiveRecord +count+ method.
       def wp_count(options, args, finder)
         excludees = [:count, :order, :limit, :offset, :readonly]
-        unless options[:select] and options[:select] =~ /^\s*DISTINCT\b/i
+
+        # we may be in a model or an association proxy
+        klass = (@owner and @reflection) ? @reflection.klass : self
+
+        # Use :select from scope if it isn't already present.
+        options[:select] = scope(:find, :select) unless options[:select]
+
+        if options[:select] and options[:select] =~ /^\s*DISTINCT\b/i
+          # Remove quoting and check for table_name.*-like statement.
+          if options[:select].gsub('`', '') =~ /\w+\.\*/
+            options[:select] = "DISTINCT #{klass.table_name}.#{klass.primary_key}"
+          end
+        else
           excludees << :select # only exclude the select param if it doesn't begin with DISTINCT
         end
 
@@ -191,10 +203,7 @@ def wp_count(options, args, finder)
         # merge the hash found in :count
         # this allows you to specify :select, :order, or anything else just for the count query
         count_options.update options[:count] if options[:count]
-
-        # we may be in a model or an association proxy
-        klass = (@owner and @reflection) ? @reflection.klass : self
-
+
         # forget about includes if they are irrelevant (Rails 2.1)
         if count_options[:include] and
             klass.private_methods.include?('references_eager_loaded_tables?') and

test/finder_test.rb

@@ -340,6 +340,12 @@ def test_count_select_when_distinct
       Developer.paginate :select => 'DISTINCT salary', :page => 2
     end
 
+    def test_count_with_scoped_select_when_distinct
+      Developer.stubs(:find).returns([])
+      Developer.expects(:count).with(:select => 'DISTINCT users.id').returns(0)
+      Developer.distinct.paginate :page => 2
+    end
+
     def test_should_use_scoped_finders_if_present
       # scope-out compatibility
       Topic.expects(:find_best).returns(Array.new(5))

test/fixtures/developer.rb

@@ -7,6 +7,7 @@ def self.with_poor_ones(&block)
     end
   end
 
+  named_scope :distinct, :select => 'DISTINCT `users`.*'
   named_scope :poor, :conditions => ['salary <= ?', 80000], :order => 'salary'
 
   def self.per_page() 10 end