Fix serializing when direct instance method call returns nil (#141)

* Fix serializing when direct instance method call returns nil

* Fix renaming anonymous class after freeze in ruby 2.7.0

lib/surrealist/builder.rb

@@ -4,7 +4,8 @@ module Surrealist
   # A class that builds a hash from the schema and type-checks the values.
   class Builder
     # Struct to carry schema along
-    Schema = Struct.new(:key, :value).freeze
+    Schema = Struct.new(:key, :value)
+    Schema.freeze
 
     # @param [Carrier] carrier instance of Surrealist::Carrier
     # @param [Hash] schema the schema defined in the object's class.

lib/surrealist/serializer.rb

@@ -107,7 +107,9 @@ def build_collection_schema(**args)
 
     # Methods not found inside serializer will be invoked on the object
     def method_missing(method, *args, &block)
-      object.public_send(method, *args, &block) || super
+      return super unless object.respond_to?(method)
+
+      object.public_send(method, *args, &block)
     end
 
     # Methods not found inside serializer will be invoked on the object

spec/serializer_spec.rb

@@ -147,6 +147,14 @@ class TestStructSerializer < Surrealist::Serializer
   json_schema { { name: String, other_param: String } }
 end
 
+class AliasSerializer < Surrealist::Serializer
+  json_schema { { param: String } }
+
+  def param
+    other_param
+  end
+end
+
 RSpec.describe Surrealist::Serializer do
   describe 'Explicit surrealization through `Serializer.new`' do
     describe 'instance' do
@@ -217,13 +225,21 @@ class TestStructSerializer < Surrealist::Serializer
         end
       end
 
-      describe 'serializing  a single struct' do
+      describe 'serializing a single struct' do
         let(:person) { TestStruct.new('John', 'Dow') }
         let(:expectation) { { name: 'John', other_param: 'Dow' } }
         subject(:hash) { TestStructSerializer.new(person).build_schema }
 
         it { is_expected.to eq expectation }
       end
+
+      describe 'serializing when direct instance method call returns nil' do
+        let(:person) { TestStruct.new('John', nil) }
+        let(:expectation) { { param: nil } }
+        subject(:hash) { AliasSerializer.new(person).build_schema }
+
+        it { is_expected.to eq expectation }
+      end
     end
 
     describe 'collection' do