Unify shapes of ActiveModel::Attributes

activemodel/lib/active_model/attribute.rb

@@ -35,30 +35,69 @@ def initialize(name, value_before_type_cast, type, original_attribute = nil, val
       @value_before_type_cast = value_before_type_cast
       @type = type
       @original_attribute = original_attribute
-      @value = value unless value.nil?
+      if value.nil?
+        @value = nil
+        @value_set = false
+      else
+        @value = value
+        @value_set = true
+      end
+      @value_for_database = nil
+      @value_for_database_set = false
     end
 
     def value
-      # `defined?` is cheaper than `||=` when we get back falsy values
-      @value = type_cast(value_before_type_cast) unless defined?(@value)
+      unless @value_set
+        @value = type_cast(value_before_type_cast)
+        @value_set = true
+      end
       @value
     end
 
-    def original_value
-      if assigned?
-        original_attribute.original_value
-      else
-        type_cast(value_before_type_cast)
-      end
+    def has_been_read?
+      @value_set
     end
 
     def value_for_database
-      if !defined?(@value_for_database) || type.changed_in_place?(@value_for_database, value)
+      if !@value_for_database_set || type.changed_in_place?(@value_for_database, value)
         @value_for_database = _value_for_database
+        @value_for_database_set = true
       end
       @value_for_database
     end
 
+    def init_with(coder)
+      @name = coder["name"]
+      @value_before_type_cast = coder["value_before_type_cast"]
+      @type = coder["type"]
+      @original_attribute = coder["original_attribute"]
+      if coder.map.key?("value")
+        @value = coder["value"]
+        @value_set = true
+      else
+        @value = nil
+        @value_set = false
+      end
+      @value_for_database = nil
+      @value_for_database_set = false
+    end
+
+    def encode_with(coder)
+      coder["name"] = name
+      coder["value_before_type_cast"] = value_before_type_cast unless value_before_type_cast.nil?
+      coder["type"] = type if type
+      coder["original_attribute"] = original_attribute if original_attribute
+      coder["value"] = value if @value_set
+    end
+
+    def original_value
+      if assigned?
+        original_attribute.original_value
+      else
+        type_cast(value_before_type_cast)
+      end
+    end
+
     def serializable?(&block)
       type.serializable?(value, &block)
     end
@@ -108,10 +147,6 @@ def came_from_user?
       false
     end
 
-    def has_been_read?
-      defined?(@value)
-    end
-
     def ==(other)
       self.class == other.class &&
         name == other.name &&
@@ -124,22 +159,6 @@ def hash
       [self.class, name, value_before_type_cast, type].hash
     end
 
-    def init_with(coder)
-      @name = coder["name"]
-      @value_before_type_cast = coder["value_before_type_cast"]
-      @type = coder["type"]
-      @original_attribute = coder["original_attribute"]
-      @value = coder["value"] if coder.map.key?("value")
-    end
-
-    def encode_with(coder)
-      coder["name"] = name
-      coder["value_before_type_cast"] = value_before_type_cast unless value_before_type_cast.nil?
-      coder["type"] = type if type
-      coder["original_attribute"] = original_attribute if original_attribute
-      coder["value"] = value if defined?(@value)
-    end
-
     def original_value_for_database
       if assigned?
         original_attribute.original_value_for_database
@@ -153,7 +172,7 @@ def original_value_for_database
       alias :assigned? :original_attribute
 
       def initialize_dup(other)
-        if defined?(@value) && @value.duplicable?
+        if has_been_read? && @value.duplicable?
           @value = @value.dup
         end
       end
@@ -181,7 +200,7 @@ def forgetting_assignment
           # changed in place, we can simply dup this attribute to avoid
           # deserialize / cast / serialize calls from computing the new
           # attribute's `value_before_type_cast`.
-          if !defined?(@value_for_database) && !changed_in_place?
+          if !@value_for_database_set && !changed_in_place?
             dup
           else
             super

activerecord/lib/active_record/marshalling.rb

@@ -2,17 +2,15 @@
 
 module ActiveRecord
   module Marshalling
-    @format_version = 6.1
+    @format_version = 7.1
 
     class << self
       attr_reader :format_version
 
       def format_version=(version)
         case version
-        when 6.1
-          Methods.remove_method(:marshal_dump) if Methods.method_defined?(:marshal_dump)
         when 7.1
-          Methods.alias_method(:marshal_dump, :_marshal_dump_7_1)
+          # do nothing
         else
           raise ArgumentError, "Unknown marshalling format: #{version.inspect}"
         end
@@ -21,7 +19,7 @@ def format_version=(version)
     end
 
     module Methods
-      def _marshal_dump_7_1
+      def marshal_dump
         payload = [attributes_for_database, new_record?]
 
         cached_associations = self.class.reflect_on_all_associations.select do |reflection|

activerecord/lib/active_record/relation/query_attribute.rb

@@ -24,7 +24,10 @@ def type_cast(value)
       end
 
       def value_for_database
-        @value_for_database = _value_for_database unless defined?(@value_for_database)
+        unless @value_for_database_set
+          @value_for_database = _value_for_database
+          @value_for_database_set = true
+        end
         @value_for_database
       end