Merge pull request #399 from ernie/join_conditions_on_join

Add association join conditions to JOIN clause, not WHERE

activerecord/lib/active_record/associations/join_dependency/join_association.rb

@@ -91,12 +91,12 @@ def join_to(relation)
 
             constraint = build_constraint(reflection, table, key, foreign_table, foreign_key)
 
-            relation.from(join(table, constraint))
-
             unless conditions[i].empty?
-              relation.where(sanitize(conditions[i], table))
+              constraint = constraint.and(sanitize(conditions[i], table))
             end
 
+            relation.from(join(table, constraint))
+
             # The current table in this iteration becomes the foreign table in the next
             foreign_table = table
           end

activerecord/test/cases/associations/inner_join_association_test.rb

@@ -34,6 +34,17 @@ def test_construct_finder_sql_ignores_empty_joins_array
     assert_no_match(/JOIN/i, sql)
   end
 
+  def test_join_conditions_added_to_join_clause
+    sql = Author.joins(:essays).to_sql
+    assert_match(/writer_type.*?=.*?Author/i, sql)
+    assert_no_match(/WHERE/i, sql)
+  end
+
+  def test_join_conditions_allow_nil_associations
+    authors = Author.includes(:essays).where(:essays => {:id => nil})
+    assert_equal 2, authors.count
+  end
+
   def test_find_with_implicit_inner_joins_honors_readonly_without_select
     authors = Author.joins(:posts).to_a
     assert !authors.empty?, "expected authors to be non-empty"