Support file_fixture in Factory definitions

Related to [factory_bot#1282][]

[rails/rails#45606][] has been merged and is likely to be released as
part of Rails 7.1.

With that addition, the path toward resolving [factory_bot#1282][]
becomes more clear. If factories can pass along [Pathname][] instances
to attachment attributes, Active Support will handle the rest.

Instances of `ActiveSupport::TestCase` provide a [file_fixture][] helper
to construct a `Pathname` instance based on the path defined by
`ActiveSupport::TestCase.file_fixture_path` (relative to the Rails root
directory).

[factory_bot#1282]: thoughtbot/factory_bot#1282 (comment)
[rails/rails#45606]: rails/rails#45606
[Pathname]: https://docs.ruby-lang.org/en/master/Pathname.html
[file_fixture]: https://api.rubyonrails.org/classes/ActiveSupport/Testing/FileFixtures.html#method-i-file_fixture

Gemfile.lock

@@ -24,12 +24,21 @@ GEM
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
+    activejob (7.1.2)
+      activesupport (= 7.1.2)
+      globalid (>= 0.3.6)
     activemodel (7.1.2)
       activesupport (= 7.1.2)
     activerecord (7.1.2)
       activemodel (= 7.1.2)
       activesupport (= 7.1.2)
       timeout (>= 0.4.0)
+    activestorage (7.1.2)
+      actionpack (= 7.1.2)
+      activejob (= 7.1.2)
+      activerecord (= 7.1.2)
+      activesupport (= 7.1.2)
+      marcel (~> 1.0)
     activesupport (7.1.2)
       base64
       bigdecimal
@@ -92,6 +101,8 @@ GEM
       activesupport (>= 5.0.0)
     ffi (1.15.5)
     ffi (1.15.5-java)
+    globalid (1.2.1)
+      activesupport (>= 6.1)
     i18n (1.14.5)
       concurrent-ruby (~> 1.0)
     io-console (0.7.2)
@@ -107,6 +118,7 @@ GEM
     loofah (2.22.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
+    marcel (1.0.4)
     mime-types (3.4.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2023.0218.1)
@@ -228,6 +240,7 @@ PLATFORMS
 
 DEPENDENCIES
   activerecord (>= 5.0.0)
+  activestorage (>= 5.0.0)
   appraisal
   aruba
   cucumber

README.md

@@ -84,6 +84,19 @@ using an empty array:
 config.factory_bot.definition_file_paths = []
 ```
 
+### File Fixture Support
+
+Factories have access to [ActiveSupport::Testing::FileFixtures#file_fixture][]
+helper to read files from tests.
+
+To disable file fixture support, set `file_fixture_support = false`:
+
+```rb
+config.factory_bot.file_fixture_support = false
+```
+
+[ActiveSupport::Testing::FileFixtures#file_fixture]: https://api.rubyonrails.org/classes/ActiveSupport/Testing/FileFixtures.html#method-i-file_fixture
+
 ### Generators
 
 Including factory\_bot\_rails in the development group of your Gemfile

Rakefile

@@ -1,6 +1,7 @@
 require "bundler/setup"
 require "cucumber/rake/task"
 require "rspec/core/rake_task"
+require "minitest/test_task"
 require "standard/rake"
 
 Bundler::GemHelper.install_tasks name: "factory_bot_rails"
@@ -12,5 +13,7 @@ end
 
 RSpec::Core::RakeTask.new(:spec)
 
+Minitest::TestTask.create
+
 desc "Run the test suite and standard"
-task default: %w[spec cucumber standard]
+task default: %w[spec test cucumber standard]

factory_bot_rails.gemspec

@@ -24,4 +24,5 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency("sqlite3")
   s.add_development_dependency("activerecord", ">= 5.0.0")
+  s.add_development_dependency("activestorage", ">= 5.0.0")
 end

lib/factory_bot_rails/file_fixture_support.rb

@@ -0,0 +1,9 @@
+module FactoryBotRails
+  module FileFixtureSupport
+    def self.included(klass)
+      klass.cattr_accessor :file_fixture_support
+
+      klass.delegate :file_fixture, to: "self.class.file_fixture_support"
+    end
+  end
+end

lib/factory_bot_rails/railtie.rb

@@ -4,13 +4,15 @@
 require "factory_bot_rails/generator"
 require "factory_bot_rails/reloader"
 require "factory_bot_rails/factory_validator"
+require "factory_bot_rails/file_fixture_support"
 require "rails"
 
 module FactoryBotRails
   class Railtie < Rails::Railtie
     config.factory_bot = ActiveSupport::OrderedOptions.new
     config.factory_bot.definition_file_paths = FactoryBot.definition_file_paths
     config.factory_bot.validator = FactoryBotRails::FactoryValidator.new
+    config.factory_bot.file_fixture_support = true
 
     initializer "factory_bot.set_fixture_replacement" do
       Generator.new(config).run
@@ -20,6 +22,22 @@ class Railtie < Rails::Railtie
       FactoryBot.definition_file_paths = definition_file_paths
     end
 
+    config.after_initialize do
+      if config.factory_bot.file_fixture_support
+        FactoryBot::SyntaxRunner.include FactoryBotRails::FileFixtureSupport
+
+        ActiveSupport.on_load :active_support_test_case do
+          setup { FactoryBot::SyntaxRunner.file_fixture_support = self }
+        end
+
+        if defined?(RSpec) && RSpec.respond_to?(:configure)
+          RSpec.configure do |config|
+            config.before { FactoryBot::SyntaxRunner.file_fixture_support = self }
+          end
+        end
+      end
+    end
+
     config.after_initialize do |app|
       FactoryBot.find_definitions
       Reloader.new(app).run

spec/dummy/db/migrate/20170806125915_create_active_storage_tables.rb

@@ -0,0 +1,57 @@
+class CreateActiveStorageTables < ActiveRecord::Migration::Current
+  def change
+    # Use Active Record's configured type for primary and foreign keys
+    primary_key_type, foreign_key_type = primary_and_foreign_key_types
+
+    create_table :active_storage_blobs, id: primary_key_type do |t|
+      t.string :key, null: false
+      t.string :filename, null: false
+      t.string :content_type
+      t.text :metadata
+      t.string :service_name, null: false
+      t.bigint :byte_size, null: false
+      t.string :checksum
+
+      if connection.supports_datetime_with_precision?
+        t.datetime :created_at, precision: 6, null: false
+      else
+        t.datetime :created_at, null: false
+      end
+
+      t.index [:key], unique: true
+    end
+
+    create_table :active_storage_attachments, id: primary_key_type do |t|
+      t.string :name, null: false
+      t.references :record, null: false, polymorphic: true, index: false, type: foreign_key_type
+      t.references :blob, null: false, type: foreign_key_type
+
+      if connection.supports_datetime_with_precision?
+        t.datetime :created_at, precision: 6, null: false
+      else
+        t.datetime :created_at, null: false
+      end
+
+      t.index [:record_type, :record_id, :name, :blob_id], name: :index_active_storage_attachments_uniqueness, unique: true
+      t.foreign_key :active_storage_blobs, column: :blob_id
+    end
+
+    create_table :active_storage_variant_records, id: primary_key_type do |t|
+      t.belongs_to :blob, null: false, index: false, type: foreign_key_type
+      t.string :variation_digest, null: false
+
+      t.index [:blob_id, :variation_digest], name: :index_active_storage_variant_records_uniqueness, unique: true
+      t.foreign_key :active_storage_blobs, column: :blob_id
+    end
+  end
+
+  private
+
+  def primary_and_foreign_key_types
+    config = Rails.configuration.generators
+    setting = config.options[config.orm][:primary_key_type]
+    primary_key_type = setting || :primary_key
+    foreign_key_type = setting || :bigint
+    [primary_key_type, foreign_key_type]
+  end
+end

spec/factory_bot_rails/factory_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe "factory extensions" do
+  describe "#file_fixture" do
+    it "delegates to the test harness" do
+      FactoryBot.define do
+        factory :upload, class: Struct.new(:filename) do
+          filename { file_fixture("file.txt") }
+        end
+      end
+
+      upload = FactoryBot.build(:upload)
+
+      expect(Pathname(upload.filename)).to eq(file_fixture("file.txt"))
+    end
+
+    it "uploads an ActiveStorage::Blob" do
+      FactoryBot.define do
+        factory :active_storage_blob, class: ActiveStorage::Blob do
+          filename { pathname.basename }
+
+          transient do
+            pathname { file_fixture("file.txt") }
+          end
+
+          after :build do |model, factory|
+            model.upload factory.pathname.open
+          end
+        end
+      end
+
+      blob = FactoryBot.create(:active_storage_blob)
+
+      expect(blob.filename.to_s).to eq("file.txt")
+      expect(blob.download).to eq(file_fixture("file.txt").read)
+    end
+  end
+end

spec/fake_app.rb

@@ -1,5 +1,10 @@
 # frozen_string_literal: true
 
+ENV["DATABASE_URL"] = "sqlite3::memory:"
+
+require "active_record/railtie"
+require "active_storage/engine"
+
 module Dummy
   class Application < Rails::Application
     config.eager_load = false
@@ -8,6 +13,14 @@ class Application < Rails::Application
     if Rails.gem_version >= Gem::Version.new("7.1")
       config.active_support.cache_format_version = 7
     end
+
+    config.active_storage.service = :local
+    config.active_storage.service_configurations = {
+      local: {
+        root: root.join("tmp/storage"),
+        service: "Disk"
+      }
+    }
   end
 end
 

spec/spec_helper.rb

@@ -4,11 +4,14 @@
 
 require "factory_bot_rails"
 require "fake_app"
+require "rspec/rails"
 
 Dir["spec/support/**/*.rb"].each { |f| require File.expand_path(f) }
 
 RSpec.configure do |config|
   config.run_all_when_everything_filtered = true
   config.filter_run :focus
   config.order = "random"
+  config.before { CreateActiveStorageTables.migrate :up }
+  config.after { CreateActiveStorageTables.migrate :down rescue nil }
 end

spec/support/active_record/migrations.rb

@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+Rails.root.glob("../dummy/db/migrate/*.rb").each { |file| require file }

test/factory_bot_rails/factory_test.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class FactoryBotRails::FactoryTest < ActiveSupport::TestCase
+  self.file_fixture_path = "test/fixtures/files"
+
+  test "delegates #file_fixture to the test harness" do
+    FactoryBot.define do
+      factory :upload, class: Struct.new(:filename) do
+        filename { file_fixture("file.txt") }
+      end
+    end
+
+    upload = FactoryBot.build(:upload)
+
+    assert_equal file_fixture("file.txt"), upload.filename
+  end
+
+  test "uploads an ActiveStorage::Blob" do
+    FactoryBot.define do
+      factory :active_storage_blob, class: ActiveStorage::Blob do
+        filename { pathname.basename }
+
+        transient do
+          pathname { file_fixture("file.txt") }
+        end
+
+        after :build do |model, factory|
+          model.upload factory.pathname.open
+        end
+      end
+    end
+
+    blob = FactoryBot.create(:active_storage_blob)
+
+    assert_equal "file.txt", blob.filename.to_s
+    assert_equal file_fixture("file.txt").read, blob.download
+  end
+end