From b52e7ca9186d7fd3c2d9736c779520d514c409ee Mon Sep 17 00:00:00 2001
From: Jakub <qoobaa@gmail.com>
Date: Thu, 16 Jul 2009 20:16:23 +0200
Subject: [PATCH] ActiveRecord::Base finders select merging

---
 activerecord/lib/active_record/base.rb         |   32 +++++++++++++++++++++-
 activerecord/test/cases/method_scoping_test.rb |   34 ++++++++++++++++++++++-
 2 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 9bc8131..ab09173 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1712,9 +1712,37 @@ module ActiveRecord #:nodoc:
           end
         end
 
+        def merge_selects(*selects)
+          distinct_select = false
+
+          selects_without_distincts = selects.compact.map do |select|
+            select_without_distinct = select.sub(/^\s*(DISTINCT|distinct)\s/, "")
+            distinct_select ||= $1
+            select_without_distinct
+          end
+
+          splitted_selects = selects_without_distincts.inject([]) { |array, select| array + select.split(",") }
+          joined_selects = splitted_selects.map(&:strip).uniq.join(",")
+
+          distinct_select ? "DISTINCT #{joined_selects}" : joined_selects
+        end
+
+        def add_selects!(sql, options, scope = :auto)
+          if options[:select] || scope && scope[:select]
+            select = merge_selects(options[:select], scope[:select])
+          else
+            select = default_select(options[:joins] || (scope && scope[:joins]))
+          end
+          sql << "#{select} "
+        end
+
         def construct_finder_sql(options)
           scope = scope(:find)
-          sql  = "SELECT #{options[:select] || (scope && scope[:select]) || default_select(options[:joins] || (scope && scope[:joins]))} "
+
+          sql  = "SELECT "
+
+          add_selects!(sql, options, scope)
+
           sql << "FROM #{options[:from]  || (scope && scope[:from]) || quoted_table_name} "
 
           add_joins!(sql, options[:joins], scope)
@@ -2142,6 +2170,8 @@ module ActiveRecord #:nodoc:
                         hash[method][key] = merge_includes(hash[method][key], params[key]).uniq
                       elsif key == :joins && merge
                         hash[method][key] = merge_joins(params[key], hash[method][key])
+                      elsif key == :select && merge
+                        hash[method][key] = merge_selects(params[key], hash[method][key])
                       else
                         hash[method][key] = hash[method][key] || params[key]
                       end
diff --git a/activerecord/test/cases/method_scoping_test.rb b/activerecord/test/cases/method_scoping_test.rb
index d8246f4..7755299 100644
--- a/activerecord/test/cases/method_scoping_test.rb
+++ b/activerecord/test/cases/method_scoping_test.rb
@@ -77,11 +77,11 @@ class MethodScopingTest < ActiveRecord::TestCase
     end
   end
 
-  def test_options_select_replaces_scope_select
+  def test_options_select_merges_scope_select
     Developer.with_scope(:find => { :select => "id, name" }) do
       developer = Developer.find(:first, :select => 'id, salary', :conditions => "name = 'David'")
       assert_equal 80000, developer.salary
-      assert !developer.has_attribute?(:name)
+      assert_equal "David", developer.name
     end
   end
 
@@ -312,6 +312,36 @@ class NestedScopingTest < ActiveRecord::TestCase
     end
   end
 
+  def test_nested_scoped_find_merged_select
+    Developer.with_scope(:find => { :select => "id" }) do
+      Developer.with_scope(:find => { :select => "salary" }) do
+        assert_equal 80000, Developer.find(:first).salary
+        assert_equal 1, Developer.find(:first).id
+        assert !Developer.find(:first).has_attribute?(:name)
+      end
+    end
+  end
+
+  def test_nested_scoped_find_merged_select_distinct
+    Developer.with_scope(:find => { :select => "DISTINCT id" }) do
+      Developer.with_scope(:find => { :select => "DISTINCT salary" }) do
+        assert_equal 80000, Developer.find(:first).salary
+        assert_equal 1, Developer.find(:first).id
+        assert !Developer.find(:first).has_attribute?(:name)
+      end
+    end
+  end
+
+  def test_nested_scoped_find_merged_select_star
+    Developer.with_scope(:find => { :select => "DISTINCT id" }) do
+      Developer.with_scope(:find => { :select => "DISTINCT *" }) do
+        assert_equal 80000, Developer.find(:first).salary
+        assert_equal 1, Developer.find(:first).id
+        assert_equal "David", Developer.find(:first).name
+      end
+    end
+  end
+
   def test_nested_scoped_find_include
     Developer.with_scope(:find => { :include => :projects }) do
       Developer.with_scope(:find => { :conditions => "projects.id = 2" }) do
-- 
1.6.0.4