Merge pull request #10796 from neerajdotname/10669

flatten merged join_values before building the joins

3 files changed, 19 insertions, 2 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 608b5b64cb..4055dcd484 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,13 @@
+*   Flatten merged join_values before building the joins.
+   
+    While joining_values special treatment is given to string values.
+    By flattening the array it ensures that string values are detected
+    as strings and not arrays.
+
+    Fixes #10669.
+
+    *Neeraj Singh and iwiznia*
+
 *   Do not load all child records for inverse case.
 
     currently `post.comments.find(Comment.first.id)` would load all
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index ca1de2d4dc..0200fcf69b 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -802,7 +802,7 @@ module ActiveRecord
     def build_arel
       arel = Arel::SelectManager.new(table.engine, table)
 
-      build_joins(arel, joins_values) unless joins_values.empty?
+      build_joins(arel, joins_values.flatten) unless joins_values.empty?
 
       collapse_wheres(arel, (where_values - ['']).uniq)
 
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 55fd068d37..693b36f35c 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -176,7 +176,7 @@ module ActiveRecord
       assert_equal ['foo = bar'], relation.where_values
     end
 
-    def test_relation_merging_with_merged_joins
+    def test_relation_merging_with_merged_joins_as_symbols
       special_comments_with_ratings = SpecialComment.joins(:ratings)
       posts_with_special_comments_with_ratings = Post.group("posts.id").joins(:special_comments).merge(special_comments_with_ratings)
       assert_equal 3, authors(:david).posts.merge(posts_with_special_comments_with_ratings).count.length
@@ -190,6 +190,13 @@ module ActiveRecord
       assert_equal false, post.respond_to?(:title), "post should not respond_to?(:body) since invoking it raises exception"
     end
 
+    def test_relation_merging_with_merged_joins_as_strings
+      join_string = "LEFT OUTER JOIN #{Rating.quoted_table_name} ON #{SpecialComment.quoted_table_name}.id = #{Rating.quoted_table_name}.comment_id"
+      special_comments_with_ratings = SpecialComment.joins join_string
+      posts_with_special_comments_with_ratings = Post.group("posts.id").joins(:special_comments).merge(special_comments_with_ratings)
+      assert_equal 3, authors(:david).posts.merge(posts_with_special_comments_with_ratings).count.length
+    end
+
   end
 
   class RelationMutationTest < ActiveSupport::TestCase