Fix merging left_joins to maintain its own `join_type` context

This fixes a regression for #35864.

Usually, stashed joins (mainly eager loading) are performed as LEFT
JOINs.
But the case of merging joins/left_joins of different class, that
(stashed) joins are performed as the same `join_type` as the parent
context for now.
Since #35864, both (joins/left_joins) stashed joins might be contained
in `joins_values`, so each stashed joins should maintain its own
`join_type` context.

Fixes #36103.

1 files changed, 10 insertions, 9 deletions

diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index b76005b587..f35a40fb2f 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -64,16 +64,17 @@ module ActiveRecord
         end
       end
 
-      def initialize(base, table, associations)
+      def initialize(base, table, associations, join_type)
         tree = self.class.make_tree associations
         @join_root = JoinBase.new(base, table, build(tree, base))
+        @join_type = join_type
       end
 
       def reflections
         join_root.drop(1).map!(&:reflection)
       end
 
-      def join_constraints(joins_to_add, join_type, alias_tracker)
+      def join_constraints(joins_to_add, alias_tracker)
         @alias_tracker = alias_tracker
 
         construct_tables!(join_root)
@@ -82,9 +83,9 @@ module ActiveRecord
         joins.concat joins_to_add.flat_map { |oj|
           construct_tables!(oj.join_root)
           if join_root.match? oj.join_root
-            walk join_root, oj.join_root
+            walk(join_root, oj.join_root, oj.join_type)
           else
-            make_join_constraints(oj.join_root, join_type)
+            make_join_constraints(oj.join_root, oj.join_type)
           end
         }
       end
@@ -125,7 +126,7 @@ module ActiveRecord
       end
 
       protected
-        attr_reader :join_root
+        attr_reader :join_root, :join_type
 
       private
         attr_reader :alias_tracker
@@ -151,7 +152,7 @@ module ActiveRecord
           end
         end
 
-        def make_constraints(parent, child, join_type = Arel::Nodes::OuterJoin)
+        def make_constraints(parent, child, join_type)
           foreign_table = parent.table
           foreign_klass = parent.base_klass
           joins = child.join_constraints(foreign_table, foreign_klass, join_type, alias_tracker)
@@ -173,13 +174,13 @@ module ActiveRecord
           join ? "#{name}_join" : name
         end
 
-        def walk(left, right)
+        def walk(left, right, join_type)
           intersection, missing = right.children.map { |node1|
             [left.children.find { |node2| node1.match? node2 }, node1]
           }.partition(&:first)
 
-          joins = intersection.flat_map { |l, r| r.table = l.table; walk(l, r) }
-          joins.concat missing.flat_map { |_, n| make_constraints(left, n) }
+          joins = intersection.flat_map { |l, r| r.table = l.table; walk(l, r, join_type) }
+          joins.concat missing.flat_map { |_, n| make_constraints(left, n, join_type) }
         end
 
         def find_reflection(klass, name)