Merge pull request #34437 from kbrock/union_all_paren

Fix: Arel now emits a single pair of parens for UNION and UNION ALL

2 files changed, 19 insertions, 32 deletions

diff --git a/activerecord/lib/arel/visitors/mysql.rb b/activerecord/lib/arel/visitors/mysql.rb
index 32f6705d04..4e7b2456aa 100644
--- a/activerecord/lib/arel/visitors/mysql.rb
+++ b/activerecord/lib/arel/visitors/mysql.rb
@@ -4,34 +4,6 @@ module Arel # :nodoc: all
   module Visitors
     class MySQL < Arel::Visitors::ToSql
       private
-        def visit_Arel_Nodes_Union(o, collector, suppress_parens = false)
-          unless suppress_parens
-            collector << "( "
-          end
-
-          case o.left
-          when Arel::Nodes::Union
-            visit_Arel_Nodes_Union o.left, collector, true
-          else
-            visit o.left, collector
-          end
-
-          collector << " UNION "
-
-          case o.right
-          when Arel::Nodes::Union
-            visit_Arel_Nodes_Union o.right, collector, true
-          else
-            visit o.right, collector
-          end
-
-          if suppress_parens
-            collector
-          else
-            collector << " )"
-          end
-        end
-
         def visit_Arel_Nodes_Bin(o, collector)
           collector << "BINARY "
           visit o.expr, collector
diff --git a/activerecord/lib/arel/visitors/to_sql.rb b/activerecord/lib/arel/visitors/to_sql.rb
index 8e56fb55a2..7efd74dbc9 100644
--- a/activerecord/lib/arel/visitors/to_sql.rb
+++ b/activerecord/lib/arel/visitors/to_sql.rb
@@ -268,13 +268,11 @@ module Arel # :nodoc: all
         end
 
         def visit_Arel_Nodes_Union(o, collector)
-          collector << "( "
-          infix_value(o, collector, " UNION ") << " )"
+          infix_value_with_paren(o, collector, " UNION ")
         end
 
         def visit_Arel_Nodes_UnionAll(o, collector)
-          collector << "( "
-          infix_value(o, collector, " UNION ALL ") << " )"
+          infix_value_with_paren(o, collector, " UNION ALL ")
         end
 
         def visit_Arel_Nodes_Intersect(o, collector)
@@ -845,6 +843,23 @@ module Arel # :nodoc: all
           visit o.right, collector
         end
 
+        def infix_value_with_paren(o, collector, value, suppress_parens = false)
+          collector << "( " unless suppress_parens
+          collector = if o.left.class == o.class
+            infix_value_with_paren(o.left, collector, value, true)
+          else
+            visit o.left, collector
+          end
+          collector << value
+          collector = if o.right.class == o.class
+            infix_value_with_paren(o.right, collector, value, true)
+          else
+            visit o.right, collector
+          end
+          collector << " )" unless suppress_parens
+          collector
+        end
+
         def aggregate(name, o, collector)
           collector << "#{name}("
           if o.distinct