Merge pull request #43511 from seanpdoyle/active-storage-overwrite-many-with-emptyish

ActiveStorage: support empty attachments submits

actionview/CHANGELOG.md

@@ -1,3 +1,16 @@
+*   Support `include_hidden:` option in calls to
+    `ActionView::Helper::FormBuilder#file_field` with `multiple: true` to
+    support submitting an empty collection of files.
 
+    ```ruby
+    form.file_field :attachments, multiple: true
+    # => <input type="hidden" autocomplete="off" name="post[attachments][]" value="">
+         <input type="file" multiple="multiple" id="post_attachments" name="post[attachments][]">
+
+    form.file_field :attachments, multiple: true, include_hidden: false
+    # => <input type="file" multiple="multiple" id="post_attachments" name="post[attachments][]">
+    ```
+
+    *Sean Doyle*
 
 Please check [7-0-stable](https://github.com/rails/rails/blob/7-0-stable/actionview/CHANGELOG.md) for previous changes.

actionview/lib/action_view/helpers/form_helper.rb

@@ -478,6 +478,8 @@ module ActionView
 
       mattr_accessor :form_with_generates_ids, default: false
 
+      mattr_accessor :multiple_file_field_include_hidden, default: false
+
       # Creates a form tag based on mixing URLs, scopes, or models.
       #
       #   # Using just a URL:
@@ -1218,6 +1220,7 @@ module ActionView
       # * Creates standard HTML attributes for the tag.
       # * <tt>:disabled</tt> - If set to true, the user will not be able to use this input.
       # * <tt>:multiple</tt> - If set to true, *in most updated browsers* the user will be allowed to select multiple files.
+      # * <tt>:include_hidden</tt> - When <tt>multiple: true</tt> and <tt>include_hidden: true</tt>, the field will be prefixed with an <tt><input type="hidden"></tt> field with an empty value to support submitting an empty collection of files.
       # * <tt>:accept</tt> - If set to one or multiple mime-types, the user will be suggested a filter when choosing a file. You still need to set up model validations.
       #
       # ==== Examples
@@ -1236,7 +1239,9 @@ module ActionView
       #   file_field(:attachment, :file, class: 'file_input')
       #   # => <input type="file" id="attachment_file" name="attachment[file]" class="file_input" />
       def file_field(object_name, method, options = {})
-        Tags::FileField.new(object_name, method, self, convert_direct_upload_option_to_url(method, options.dup)).render
+        options = { include_hidden: multiple_file_field_include_hidden }.merge!(options)
+
+        Tags::FileField.new(object_name, method, self, convert_direct_upload_option_to_url(method, options)).render
       end
 
       # Returns a textarea opening and closing tag set tailored for accessing a specified attribute (identified by +method+)
@@ -2489,6 +2494,7 @@ module ActionView
       # * Creates standard HTML attributes for the tag.
       # * <tt>:disabled</tt> - If set to true, the user will not be able to use this input.
       # * <tt>:multiple</tt> - If set to true, *in most updated browsers* the user will be allowed to select multiple files.
+      # * <tt>:include_hidden</tt> - When <tt>multiple: true</tt> and <tt>include_hidden: true</tt>, the field will be prefixed with an <tt><input type="hidden"></tt> field with an empty value to support submitting an empty collection of files.
       # * <tt>:accept</tt> - If set to one or multiple mime-types, the user will be suggested a filter when choosing a file. You still need to set up model validations.
       #
       # ==== Examples

actionview/lib/action_view/helpers/tags/file_field.rb

@@ -4,6 +4,22 @@ module ActionView
   module Helpers
     module Tags # :nodoc:
       class FileField < TextField # :nodoc:
+        def render
+          include_hidden = @options.delete(:include_hidden)
+          options = @options.stringify_keys
+          add_default_name_and_id(options)
+
+          if options["multiple"] && include_hidden
+            hidden_field_for_multiple_file(options) + super
+          else
+            super
+          end
+        end
+
+        private
+          def hidden_field_for_multiple_file(options)
+            tag("input", "name" => options["name"], "type" => "hidden", "value" => "", "autocomplete" => "off")
+          end
       end
     end
   end

actionview/test/template/form_helper_test.rb

@@ -552,11 +552,38 @@ class FormHelperTest < ActionView::TestCase
     assert_dom_equal expected, file_field("import", "file", multiple: true)
   end
 
+  def test_file_field_with_multiple_behavior_configured_include_hidden
+    old_value = ActionView::Helpers::FormHelper.multiple_file_field_include_hidden
+    ActionView::Helpers::FormHelper.multiple_file_field_include_hidden = true
+
+    expected = '<input type="hidden" name="import[file][]" autocomplete="off" value="">' \
+               '<input id="import_file" multiple="multiple" name="import[file][]" type="file" />'
+    assert_dom_equal expected, file_field("import", "file", multiple: true)
+  ensure
+    ActionView::Helpers::FormHelper.multiple_file_field_include_hidden = old_value
+  end
+
+  def test_file_field_with_multiple_behavior_include_hidden_false
+    expected = '<input id="import_file" multiple="multiple" name="import[file][]" type="file" />'
+    assert_dom_equal expected, file_field("import", "file", multiple: true, include_hidden: false)
+  end
+
   def test_file_field_with_multiple_behavior_and_explicit_name
     expected = '<input id="import_file" multiple="multiple" name="custom" type="file" />'
     assert_dom_equal expected, file_field("import", "file", multiple: true, name: "custom")
   end
 
+  def test_file_field_with_multiple_behavior_and_explicit_name_configured_include_hidden
+    old_value = ActionView::Helpers::FormHelper.multiple_file_field_include_hidden
+    ActionView::Helpers::FormHelper.multiple_file_field_include_hidden = true
+
+    expected = '<input type="hidden" name="custom" autocomplete="off" value="">' \
+               '<input id="import_file" multiple="multiple" name="custom" type="file" />'
+    assert_dom_equal expected, file_field("import", "file", multiple: true, name: "custom")
+  ensure
+    ActionView::Helpers::FormHelper.multiple_file_field_include_hidden = old_value
+  end
+
   def test_file_field_with_direct_upload_when_rails_direct_uploads_url_is_not_defined
     expected = '<input type="file" name="import[file]" id="import_file" />'
     assert_dom_equal expected, file_field("import", "file", direct_upload: true)

activestorage/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Support transforming empty-ish `has_many_attached` value into `[]` (e.g. `[""]`)
 
+    ```ruby
+    @user.highlights = [""]
+    @user.highlights # => []
+    ```
+
+    *Sean Doyle*
 
 Please check [7-0-stable](https://github.com/rails/rails/blob/7-0-stable/activestorage/CHANGELOG.md) for previous changes.

activestorage/lib/active_storage/attached/model.rb

@@ -137,9 +137,11 @@ module ActiveStorage
           end
 
           def #{name}=(attachables)
+            attachables = Array(attachables).compact_blank
+
             if ActiveStorage.replace_on_assign_to_many
               attachment_changes["#{name}"] =
-                if Array(attachables).none?
+                if attachables.none?
                   ActiveStorage::Attached::Changes::DeleteMany.new("#{name}", self)
                 else
                   ActiveStorage::Attached::Changes::CreateMany.new("#{name}", self, attachables)
@@ -151,7 +153,7 @@ module ActiveStorage
                 "To append new attachables to the Active Storage association, prefer using `attach`. " \
                 "Using association setter would result in purging the existing attached attachments and replacing them with new ones."
 
-              if Array(attachables).any?
+              if attachables.any?
                 attachment_changes["#{name}"] =
                   ActiveStorage::Attached::Changes::CreateMany.new("#{name}", self, #{name}.blobs + attachables)
               end

activestorage/lib/active_storage/engine.rb

@@ -154,6 +154,18 @@ module ActiveStorage
       end
     end
 
+    initializer "action_view.configuration" do
+      config.after_initialize do |app|
+        ActiveSupport.on_load(:action_view) do
+          multiple_file_field_include_hidden = app.config.active_storage.delete(:multiple_file_field_include_hidden)
+
+          unless multiple_file_field_include_hidden.nil?
+            ActionView::Helpers::FormHelper.multiple_file_field_include_hidden = multiple_file_field_include_hidden
+          end
+        end
+      end
+    end
+
     initializer "active_storage.asset" do
       if Rails.application.config.respond_to?(:assets)
         Rails.application.config.assets.precompile += %w( activestorage activestorage.esm )

activestorage/test/models/attached/many_test.rb

@@ -209,6 +209,22 @@ class ActiveStorage::ManyAttachedTest < ActiveSupport::TestCase
     assert_equal "wherever.mp4", @user.vlogs.second.filename.to_s
   end
 
+  test "replacing attachments with an empty list" do
+    @user.highlights = []
+    assert_empty @user.highlights
+  end
+
+  test "replacing attachments with a list containing empty items" do
+    @user.highlights = [""]
+    assert_empty @user.highlights
+  end
+
+  test "replacing attachments with a list containing a mixture of empty and present items" do
+    @user.highlights = [ "", fixture_file_upload("racecar.jpg") ]
+    assert_equal 1, @user.highlights.size
+    assert_equal "racecar.jpg", @user.highlights.first.filename.to_s
+  end
+
   test "successfully updating an existing record to replace existing, dependent attachments" do
     [ create_blob(filename: "funky.jpg"), create_blob(filename: "town.jpg") ].tap do |old_blobs|
       @user.highlights.attach old_blobs

guides/source/configuring.md

@@ -1719,6 +1719,13 @@ config.active_storage.video_preview_arguments = "-vf 'select=eq(n\\,0)+eq(key\\,
 1. `select=eq(n\,0)+eq(key\,1)+gt(scene\,0.015)`: Select the first video frame, plus keyframes, plus frames that meet the scene change threshold.
 2. `loop=loop=-1:size=2,trim=start_frame=1`: To use the first video frame as a fallback when no other frames meet the criteria, loop the first (one or) two selected frames, then drop the first looped frame.
 
+#### `config.active_storage.multiple_file_field_include_hidden`
+
+In Rails 7.1 and beyond, Active Storage `has_many_attached` relationships will
+default to _replacing_ the current collection instead of _appending_ to it. To
+support submitting an _empty_ collection, render an auxiliary hidden field
+similar to how Action View Form Builder render checkbox elements.
+
 ### Configuring Action Text
 
 #### `config.action_text.attachment_tag_name`
@@ -1747,6 +1754,7 @@ Accepts a string for the HTML tag used to wrap attachments. Defaults to `"action
 - `config.action_dispatch.return_only_request_media_type_on_content_type`: `false`
 - `config.action_mailer.smtp_timeout`: `5`
 - `config.active_storage.video_preview_arguments`: `"-vf 'select=eq(n\\,0)+eq(key\\,1)+gt(scene\\,0.015),loop=loop=-1:size=2,trim=start_frame=1' -frames:v 1 -f image2"`
+- `config.active_storage.multiple_file_field_include_hidden`: `true`
 - `config.active_record.automatic_scope_inversing`: `true`
 - `config.active_record.verify_foreign_keys_for_fixtures`: `true`
 - `config.active_record.partial_inserts`: `false`
@@ -1845,6 +1853,7 @@ Accepts a string for the HTML tag used to wrap attachments. Defaults to `"action
 - `ActiveSupport.utc_to_local_returns_utc_offset_times`: `false`
 - `config.action_mailer.smtp_timeout`: `nil`
 - `config.active_storage.video_preview_arguments`: `"-y -vframes 1 -f image2"`
+- `config.active_storage.multiple_file_field_include_hidden`: `false`
 - `config.active_storage.variant_processor`: `:mini_magick`
 - `config.action_controller.wrap_parameters_by_default`: `false`
 - `config.action_dispatch.default_headers`:

railties/lib/rails/application/configuration.rb

@@ -236,6 +236,7 @@ module Rails
               " -frames:v 1 -f image2"
 
             active_storage.variant_processor = :vips
+            active_storage.multiple_file_field_include_hidden = true
           end
 
           if respond_to?(:active_record)