Fix unscope with subquery

Currently cannot unscope subquery properly.
This commit fixes the issue.

Fixes rails#26323.

Author: kamipo

activerecord/lib/active_record/relation/where_clause.rb

@@ -25,10 +25,7 @@ def merge(other)
       end
 
       def except(*columns)
-        WhereClause.new(
-          predicates_except(columns),
-          binds_except(columns),
-        )
+        WhereClause.new(*except_predicates_and_binds(columns))
       end
 
       def or(other)
@@ -132,20 +129,32 @@ def invert_predicate(node)
           end
         end
 
-        def predicates_except(columns)
-          predicates.reject do |node|
+        def except_predicates_and_binds(columns)
+          except_binds = []
+          binds_index = 0
+
+          predicates = self.predicates.reject do |node|
             case node
             when Arel::Nodes::Between, Arel::Nodes::In, Arel::Nodes::NotIn, Arel::Nodes::Equality, Arel::Nodes::NotEqual, Arel::Nodes::LessThan, Arel::Nodes::LessThanOrEqual, Arel::Nodes::GreaterThan, Arel::Nodes::GreaterThanOrEqual
+              binds_contains = node.grep(Arel::Nodes::BindParam).size
               subrelation = (node.left.kind_of?(Arel::Attributes::Attribute) ? node.left : node.right)
               columns.include?(subrelation.name.to_s)
+            end.tap do |except|
+              if except && binds_contains > 0
+                (binds_index...(binds_index + binds_contains)).each do |i|
+                  except_binds[i] = true
+                end
+
+                binds_index += binds_contains
+              end
             end
           end
-        end
 
-        def binds_except(columns)
-          binds.reject do |attr|
-            columns.include?(attr.name)
+          binds = self.binds.reject.with_index do |_, i|
+            except_binds[i]
           end
+
+          [predicates, binds]
         end
 
         def predicates_with_wrapped_sql_literals

activerecord/test/cases/relations_test.rb

@@ -1962,6 +1962,18 @@ def test_presence
     assert !Post.all.respond_to?(:by_lifo)
   end
 
+  def test_unscope_with_subquery
+    p1 = Post.where(id: 1)
+    p2 = Post.where(id: 2)
+
+    assert_not_equal p1, p2
+
+    comments = Comment.where(post: p1).unscope(where: :post_id).where(post: p2)
+
+    assert_not_equal p1.first.comments, comments
+    assert_equal p2.first.comments, comments
+  end
+
   def test_unscope_removes_binds
     left = Post.where(id: Arel::Nodes::BindParam.new)
     column = Post.columns_hash["id"]