When using rack-test 2, we no longer need to send NilUploadedFile to trigger multipart

Gemfile

@@ -7,6 +7,8 @@ gemspec
 
 gem 'xpath', github: 'teamcapybara/xpath'
 
+# gem 'rack-test', github: 'rack/rack-test'
+
 group :doc do
   gem 'redcarpet', platforms: :mri
 end

lib/capybara/rack_test/browser.rb

@@ -31,11 +31,17 @@ class Capybara::RackTest::Browser
     request(last_request.fullpath, last_request.env)
   end
 
-  def submit(method, path, attributes)
+  def submit(method, path, attributes, content_type: nil)
     path = request_path if path.nil? || path.empty?
     uri = build_uri(path)
     uri.query = '' if method.to_s.casecmp('get').zero?
-    process_and_follow_redirects(method, uri.to_s, attributes, 'HTTP_REFERER' => referer_url)
+    process_and_follow_redirects(
+      method,
+      uri.to_s,
+      attributes,
+      'HTTP_REFERER' => referer_url,
+      'CONTENT_TYPE' => content_type
+    )
   end
 
   def follow(method, path, **attributes)

lib/capybara/rack_test/form.rb

@@ -30,19 +30,31 @@ class Capybara::RackTest::Form < Capybara::RackTest::Node
 
     form_elements = native.xpath(form_elements_xpath).reject { |el| submitter?(el) && (el != button.native) }
 
-    form_elements.each_with_object(make_params) do |field, params|
+    form_params = form_elements.each_with_object({}.compare_by_identity) do |field, params|
       case field.name
       when 'input', 'button' then add_input_param(field, params)
       when 'select' then add_select_param(field, params)
       when 'textarea' then add_textarea_param(field, params)
       end
+    end
+
+    form_params.each_with_object(make_params) do |(name, value), params|
+      merge_param!(params, name, value)
     end.to_params_hash
+
+    # form_elements.each_with_object(make_params) do |field, params|
+    #   case field.name
+    #   when 'input', 'button' then add_input_param(field, params)
+    #   when 'select' then add_select_param(field, params)
+    #   when 'textarea' then add_textarea_param(field, params)
+    #   end
+    # end.to_params_hash
   end
 
   def submit(button)
     action = button&.[]('formaction') || native['action']
     method = button&.[]('formmethod') || request_method
-    driver.submit(method, action.to_s, params(button))
+    driver.submit(method, action.to_s, params(button), content_type: native['enctype'])
   end
 
   def multipart?
@@ -88,6 +100,8 @@ private
 
       Capybara::RackTest::Node.new(driver, field).value.to_s
     when 'file'
+      return if value.empty? && params.keys.include?(name) && Rack::Test::VERSION.to_f >= 2.0 # rubocop:disable Performance/InefficientHashSearch
+
       if multipart?
         file_to_upload(value)
       else
@@ -96,7 +110,8 @@ private
     else
       value
     end
-    merge_param!(params, name, value)
+    # merge_param!(params, name, value)
+    params[name] = value
   end
 
   def file_to_upload(filename)
@@ -109,18 +124,23 @@ private
   end
 
   def add_select_param(field, params)
+    name = field['name']
     if field.has_attribute?('multiple')
-      field.xpath('.//option[@selected]').each do |option|
-        merge_param!(params, field['name'], (option['value'] || option.text).to_s)
+      value = field.xpath('.//option[@selected]').map do |option|
+        # merge_param!(params, field['name'], (option['value'] || option.text).to_s)
+        (option['value'] || option.text).to_s
       end
+      params[name] = value unless value.empty?
     else
       option = field.xpath('.//option[@selected]').first || field.xpath('.//option').first
-      merge_param!(params, field['name'], (option['value'] || option.text).to_s) if option
+      # merge_param!(params, field['name'], (option['value'] || option.text).to_s) if option
+      params[name] = (option['value'] || option.text).to_s if option
     end
   end
 
   def add_textarea_param(field, params)
-    merge_param!(params, field['name'], field['_capybara_raw_value'].to_s.gsub(/\r?\n/, "\r\n"))
+    # merge_param!(params, field['name'], field['_capybara_raw_value'].to_s.gsub(/\r?\n/, "\r\n"))
+    params[field['name']] = field['_capybara_raw_value'].to_s.gsub(/\r?\n/, "\r\n")
   end
 
   def submitter?(el)

lib/capybara/spec/session/attach_file_spec.rb

@@ -55,6 +55,12 @@ Capybara::SpecHelper.spec '#attach_file' do
       expect(@session).to have_content('No file uploaded')
     end
 
+    it 'should send prior hidden field if no file submitted' do
+      @session.click_button('Upload Empty With Hidden')
+      expect(extract_results(@session)['document2']).to eq('hidden_field')
+      expect(extract_content_type(@session)).to start_with('multipart/form-data;')
+    end
+
     it 'should send content type text/plain when uploading a text file' do
       @session.attach_file 'Single Document', with_os_path_separators(test_file_path)
       @session.click_button 'Upload Single'

lib/capybara/spec/spec_helper.rb

@@ -122,6 +122,11 @@ module Capybara
       YAML.safe_load results, permitted_classes: perms
     end
 
+    def extract_content_type(session)
+      expect(session).to have_xpath("//pre[@id='content_type']")
+      Capybara::HTML(session.body).xpath("//pre[@id='content_type']").first.text
+    end
+
     def be_an_invalid_element_error(session)
       satisfy { |error| session.driver.invalid_element_errors.any? { |e| error.is_a? e } }
     end

lib/capybara/spec/test_app.rb

@@ -256,12 +256,15 @@ class TestApp < Sinatra::Base
 
   post '/form' do
     self.class.form_post_count += 1
-    %(<pre id="results">#{params[:form].merge('post_count' => self.class.form_post_count).to_yaml}</pre>)
+    %(
+      <pre id="content_type">#{request.content_type}</pre>
+      <pre id="results">#{params.fetch(:form, {}).merge('post_count' => self.class.form_post_count).to_yaml}</pre>
+    )
   end
 
   post '/upload_empty' do
     if params[:form][:file].nil?
-      'Successfully ignored empty file field.'
+      "Successfully ignored empty file field. Content type was #{request.content_type}"
     else
       'Something went wrong.'
     end

lib/capybara/spec/views/form.erb

@@ -586,6 +586,19 @@ New line after and before textarea tag
   <p>
 </form>
 
+<form action="/form" method="post" enctype="multipart/form-data">
+  <input type="hidden" name="form[document2]" value="hidden_field"/>
+
+  <p>
+    <label for="form_document">Document with hidden</label>
+    <input type="file" name="form[document2]" id="form_document2"/>
+  </p>
+
+  <p>
+    <input type="submit" value="Upload Empty With Hidden"/>
+  <p>
+</form>
+
 <form action="/upload_multiple" method="post" enctype="multipart/form-data">
   <p>
     <label for="form_multiple_file_name">File Name</label>

spec/dsl_spec.rb

@@ -15,6 +15,8 @@ Capybara::SpecHelper.run_specs TestClass.new, 'DSL', capybara_skip: %i[
     pending "Nokogiri doesn't support case insensitive CSS attribute matchers"
   when /#click_button should follow permanent redirects that maintain method/
     pending "Rack < 2 doesn't support 308" if Gem.loaded_specs['rack'].version < Gem::Version.new('2.0.0')
+  when /#attach_file with multipart form should send prior hidden field if no file submitted/
+    skip 'Rack-test < 2 needs an empty file to detect multipart form' if Gem.loaded_specs['rack-test'].version < Gem::Version.new('2.0.0')
   end
 end
 

spec/rack_test_spec.rb

@@ -30,6 +30,8 @@ Capybara::SpecHelper.run_specs TestSessions::RackTest, 'RackTest', capybara_skip
     skip "Nokogiri doesn't support case insensitive CSS attribute matchers"
   when /#click_button should follow permanent redirects that maintain method/
     skip "Rack < 2 doesn't support 308" if Gem.loaded_specs['rack'].version < Gem::Version.new('2.0.0')
+  when /#attach_file with multipart form should send prior hidden field if no file submitted/
+    skip 'Rack-test < 2 needs an empty file to detect multipart form' if Gem.loaded_specs['rack-test'].version < Gem::Version.new('2.0.0')
   end
 end
 
@@ -93,6 +95,12 @@ RSpec.describe Capybara::Session do # rubocop:disable RSpec/MultipleDescribes
           session.click_button('Upload Empty')
           expect(session.html).to include('Successfully ignored empty file field.')
         end
+
+        it 'should submit multipart even if no file is submitted' do
+          session.visit('/form')
+          session.click_button('Upload Empty')
+          expect(session.html).to include('Content type was multipart/form-data;')
+        end
       end
 
       it 'should not submit an obsolete mime type' do