Skip validation for a file if it is optional and nil

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 #### Fixes
 
+* [#1977](https://github.com/ruby-grape/grape/pull/1977): Skip validation for a file if it is optional and nil - [@dnesteryuk](https://github.com/dnesteryuk).
 * [#1976](https://github.com/ruby-grape/grape/pull/1976): Ensure classes/modules listed for autoload really exist - [@dnesteryuk](https://github.com/dnesteryuk).
 * [#1971](https://github.com/ruby-grape/grape/pull/1971): Fix BigDecimal coercion - [@FlickStuart](https://github.com/FlickStuart).
 * [#1968](https://github.com/ruby-grape/grape/pull/1968): Fix args forwarding in Grape::Middleware::Stack#merge_with for ruby 2.7.0 - [@dm1try](https://github.com/dm1try).

lib/grape/validations/types/file.rb

@@ -8,6 +8,7 @@ module Types
  # this class is here only to assert that rack's handling has succeeded.
  class File
  def call(input)
+ return if input.nil?
  return InvalidValue.new unless coerced?(input)
 
  # Processing of multipart file objects

spec/grape/validations_spec.rb

@@ -11,14 +11,17 @@ def app
 
  describe 'params' do
  context 'optional' do
- it 'validates when params is present' do
+ before do
  subject.params do
  optional :a_number, regexp: /^[0-9]+$/
+ optional :attachment, type: File
  end
  subject.get '/optional' do
  'optional works!'
  end
+ end
 
+ it 'validates when params is present' do
  get '/optional', a_number: 'string'
  expect(last_response.status).to eq(400)
  expect(last_response.body).to eq('a_number is invalid')
@@ -29,14 +32,7 @@ def app
  end
 
  it "doesn't validate when param not present" do
- subject.params do
- optional :a_number, regexp: /^[0-9]+$/
- end
- subject.get '/optional' do
- 'optional works!'
- end
-
- get '/optional'
+ get '/optional', a_number: nil, attachment: nil
  expect(last_response.status).to eq(200)
  expect(last_response.body).to eq('optional works!')
  end