Prevent making bind param if casted value is nil

If casted value is nil, generated SQL should be `IS NULL`. But currently
it is generated as `= NULL`. To prevent this behavior, avoid making bind
param if casted value is nil.

Fixes #28945.

5 files changed, 24 insertions, 9 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 1f8163db12..f75f1a9108 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Prevent making bind param if casted value is nil.
+
+    *Ryuta Kamizono*
+
 *   Deprecate passing arguments and block at the same time to `count` and `sum` in `ActiveRecord::Calculations`.
 
     *Ryuta Kamizono*
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index a6309e0b5c..7dea5deec5 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -107,21 +107,26 @@ module ActiveRecord
             first = value.begin
             last = value.end
             unless first.respond_to?(:infinite?) && first.infinite?
-              binds << build_bind_param(column_name, first)
+              binds << build_bind_attribute(column_name, first)
               first = Arel::Nodes::BindParam.new
             end
             unless last.respond_to?(:infinite?) && last.infinite?
-              binds << build_bind_param(column_name, last)
+              binds << build_bind_attribute(column_name, last)
               last = Arel::Nodes::BindParam.new
             end
 
             result[column_name] = RangeHandler::RangeWithBinds.new(first, last, value.exclude_end?)
+          when value.is_a?(Relation)
+            binds.concat(value.bound_attributes)
           else
             if can_be_bound?(column_name, value)
-              result[column_name] = Arel::Nodes::BindParam.new
-              binds << build_bind_param(column_name, value)
-            elsif value.is_a?(Relation)
-              binds.concat(value.bound_attributes)
+              bind_attribute = build_bind_attribute(column_name, value)
+              if value.is_a?(StatementCache::Substitute) || !bind_attribute.value_for_database.nil?
+                result[column_name] = Arel::Nodes::BindParam.new
+                binds << bind_attribute
+              else
+                result[column_name] = nil
+              end
             end
           end
         end
@@ -164,7 +169,7 @@ module ActiveRecord
         end
       end
 
-      def build_bind_param(column_name, value)
+      def build_bind_attribute(column_name, value)
         Relation::QueryAttribute.new(column_name.to_s, value, table.type(column_name))
       end
   end
diff --git a/activerecord/lib/active_record/relation/where_clause_factory.rb b/activerecord/lib/active_record/relation/where_clause_factory.rb
index 04bee73e8f..b862dd56a5 100644
--- a/activerecord/lib/active_record/relation/where_clause_factory.rb
+++ b/activerecord/lib/active_record/relation/where_clause_factory.rb
@@ -57,7 +57,7 @@ module ActiveRecord
             else
               column = klass.column_for_attribute(attribute)
 
-              binds << predicate_builder.send(:build_bind_param, attribute, value)
+              binds << predicate_builder.send(:build_bind_attribute, attribute, value)
               value = Arel::Nodes::BindParam.new
 
               predicate = if options[:case_sensitive]
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index db3da53487..4ef9a125e6 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -60,6 +60,7 @@ class EnumTest < ActiveRecord::TestCase
     assert_not_equal @book, Book.where(status: [:written]).first
     assert_not_equal @book, Book.where.not(status: :published).first
     assert_equal @book, Book.where.not(status: :written).first
+    assert_equal books(:ddd), Book.where(read_status: :forgotten).first
   end
 
   test "find via where with strings" do
@@ -69,6 +70,7 @@ class EnumTest < ActiveRecord::TestCase
     assert_not_equal @book, Book.where(status: ["written"]).first
     assert_not_equal @book, Book.where.not(status: "published").first
     assert_equal @book, Book.where.not(status: "written").first
+    assert_equal books(:ddd), Book.where(read_status: "forgotten").first
   end
 
   test "build from scope" do
diff --git a/activerecord/test/cases/relation/where_test.rb b/activerecord/test/cases/relation/where_test.rb
index cbc466d6b8..42dae4d569 100644
--- a/activerecord/test/cases/relation/where_test.rb
+++ b/activerecord/test/cases/relation/where_test.rb
@@ -15,7 +15,7 @@ require "models/vertex"
 
 module ActiveRecord
   class WhereTest < ActiveRecord::TestCase
-    fixtures :posts, :edges, :authors, :author_addresses, :binaries, :essays, :cars, :treasures, :price_estimates
+    fixtures :posts, :edges, :authors, :author_addresses, :binaries, :essays, :cars, :treasures, :price_estimates, :topics
 
     def test_where_copies_bind_params
       author = authors(:david)
@@ -48,6 +48,10 @@ module ActiveRecord
       assert_equal [chef], chefs.to_a
     end
 
+    def test_where_with_casted_value_is_nil
+      assert_equal 4, Topic.where(last_read: "").count
+    end
+
     def test_rewhere_on_root
       assert_equal posts(:welcome), Post.rewhere(title: "Welcome to the weblog").first
     end