fix serialize Struct, now Struct is not a collection

lib/surrealist/helper.rb

@@ -16,7 +16,9 @@ def self.collection?(object)
       # 4.2 AR relation object did not include Enumerable (it defined
       # all necessary method through ActiveRecord::Delegation module),
       # so we need to explicitly check for this
-      (object.is_a?(Enumerable) && !object.instance_of?(Hash)) || ar_relation?(object)
+      return false if object.is_a?(Struct)
+
+      object.is_a?(Enumerable) && !object.instance_of?(Hash) || ar_relation?(object)
     end
 
     def self.ar_relation?(object)

spec/helper_spec.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+TestStruct = Struct.new(:name, :other_param)
+
+RSpec.describe Surrealist::Helper do
+  describe 'serializing  a single struct' do
+    let(:person) { TestStruct.new('John', 'Dow') }
+
+    specify 'a struct is not treated as a collection' do
+      expect(Surrealist::Helper.collection?(person)).to eq false
+    end
+  end
+end

spec/serializer_spec.rb

@@ -141,6 +141,12 @@ class FooChildSerializer < FooSerializer
   end
 end
 
+TestStruct = Struct.new(:name, :other_param)
+
+class TestStructSerializer < Surrealist::Serializer
+  json_schema { { name: String, other_param: String } }
+end
+
 RSpec.describe Surrealist::Serializer do
   describe 'Explicit surrealization through `Serializer.new`' do
     describe 'instance' do
@@ -210,6 +216,14 @@ class FooChildSerializer < FooSerializer
           it { is_expected.to eq expectation }
         end
       end
+
+      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
     end
 
     describe 'collection' do
@@ -250,6 +264,24 @@ class FooChildSerializer < FooSerializer
           it { is_expected.to eq expectation }
         end
       end
+
+      describe 'collection of structs' do
+        let(:person1) { TestStruct.new('John', 'Dow') }
+        let(:person2) { TestStruct.new('Mountain', 'Dew') }
+        let(:person3) { TestStruct.new('Harley', 'Queen') }
+        let(:struct_collection) { [person1, person2, person3] }
+        let(:expectation) do
+          [
+            { name: 'John', other_param: 'Dow' },
+            { name: 'Mountain', other_param: 'Dew' },
+            { name: 'Harley', other_param: 'Queen' },
+          ]
+        end
+
+        subject(:json) { TestStructSerializer.new(struct_collection).build_schema }
+
+        it { is_expected.to eq expectation }
+      end
     end
   end