add if/unless options to attribute

Author: LcpMarvel

lib/active_model/serializer.rb

@@ -33,6 +33,8 @@ class Serializer
       self._attributes ||= []
       class_attribute :_attributes_keys
       self._attributes_keys ||= {}
+      class_attribute :_attributes_conditions
+      self._attributes_conditions ||= {}
       serializer.class_attribute :_cache
       serializer.class_attribute :_fragmented
       serializer.class_attribute :_cache_key
@@ -45,6 +47,7 @@ class Serializer
     def self.inherited(base)
       base._attributes = _attributes.dup
       base._attributes_keys = _attributes_keys.dup
+      base._attributes_conditions = _attributes_conditions.dup
       base._cache_digest = digest_caller_file(caller.first)
       super
     end
@@ -54,10 +57,11 @@ def self.type(type)
     end
 
     def self.attributes(*attrs)
+      options = attrs.last.class == Hash ? attrs.pop : {}
       attrs = attrs.first if attrs.first.class == Array
 
       attrs.each do |attr|
-        attribute(attr)
+        attribute(attr, options)
       end
     end
 
@@ -66,6 +70,17 @@ def self.attribute(attr, options = {})
       _attributes_keys[attr] = { key: key } if key != attr
       _attributes << key unless _attributes.include?(key)
 
+      [:if, :unless].each do |switch|
+        next unless options.key?(switch)
+        condition = { switch => options[switch] }
+
+        if _attributes_conditions[condition]
+          _attributes_conditions[condition] << key
+        else
+          _attributes_conditions[condition] = [key]
+        end
+      end
+
       ActiveModelSerializers.silence_warnings do
         define_method key do
           object.read_attribute_for_serialization(attr)
@@ -160,7 +175,7 @@ def json_key
     end
 
     def attributes
-      attributes = self.class._attributes.dup
+      attributes = self.class._attributes.dup - useless_attributes_keys
 
       attributes.each_with_object({}) do |name, hash|
         if self.class._fragmented
@@ -171,8 +186,31 @@ def attributes
       end
     end
 
+    def useless_attributes_keys
+      self.class
+        ._attributes_conditions
+        .dup
+        .each_with_object([]) do |(switch_hash, keys), useless_keys|
+        case switch_hash.keys
+        when [:if]
+          useless_keys << keys unless judge_attribute(switch_hash[:if])
+        when [:unless]
+          useless_keys << keys if judge_attribute(switch_hash[:unless])
+        else
+          useless_keys
+        end
+      end.flatten
+    end
+
     protected
 
     attr_accessor :instance_options
+
+    private
+
+    def judge_attribute(condition)
+      (condition.is_a?(Symbol) && send(condition)) ||
+        (condition.respond_to?(:call) && condition.call)
+    end
   end
 end

test/serializers/attribute_test.rb

@@ -71,6 +71,22 @@ def id
 
         assert_equal('custom', hash[:blog][:id])
       end
+
+      def test_attributes_conditions
+        serializer_class = Class.new(ActiveModel::Serializer) do
+          attribute :id
+          attributes :name, :title, if: :admin?
+          attribute :type, unless: proc { true }
+
+          def admin?
+            false
+          end
+        end
+        serializer = serializer_class.new(@blog)
+
+        assert_equal([:name, :title, :type], serializer.useless_attributes_keys)
+        assert_equal({ id: 1 }, serializer.attributes)
+      end
     end
   end
 end