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

Author: seanpdoyle

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]

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 +1,56 @@
+class CreateActiveStorageTables < ActiveRecord::Migration[7.0]
+  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/dummy/db/migrate/20190112182829_add_service_name_to_active_storage_blobs.rb

@@ -0,0 +1,21 @@
+class AddServiceNameToActiveStorageBlobs < ActiveRecord::Migration[6.0]
+  def up
+    return unless table_exists?(:active_storage_blobs)
+
+    unless column_exists?(:active_storage_blobs, :service_name)
+      add_column :active_storage_blobs, :service_name, :string
+
+      if configured_service = ActiveStorage::Blob.service.name
+        ActiveStorage::Blob.unscoped.update_all(service_name: configured_service)
+      end
+
+      change_column :active_storage_blobs, :service_name, :string, null: false
+    end
+  end
+
+  def down
+    return unless table_exists?(:active_storage_blobs)
+
+    remove_column :active_storage_blobs, :service_name
+  end
+end

spec/dummy/db/migrate/20191206030411_create_active_storage_variant_records.rb

@@ -0,0 +1,26 @@
+class CreateActiveStorageVariantRecords < ActiveRecord::Migration[6.0]
+  def change
+    return unless table_exists?(:active_storage_blobs)
+
+    # Use Active Record's configured type for primary key
+    create_table :active_storage_variant_records, id: primary_key_type, if_not_exists: true do |t|
+      t.belongs_to :blob, null: false, index: false, type: blobs_primary_key_type
+      t.string :variation_digest, null: false
+
+      t.index %i[ 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_key_type
+      config = Rails.configuration.generators
+      config.options[config.orm][:primary_key_type] || :primary_key
+    end
+
+    def blobs_primary_key_type
+      pkey_name = connection.primary_key(:active_storage_blobs)
+      pkey_column = connection.columns(:active_storage_blobs).find { |c| c.name == pkey_name }
+      pkey_column.bigint? ? :bigint : pkey_column.type
+    end
+end

spec/dummy/db/migrate/20211119233751_remove_not_null_on_active_storage_blobs_checksum.rb

@@ -0,0 +1,7 @@
+class RemoveNotNullOnActiveStorageBlobsChecksum < ActiveRecord::Migration[6.0]
+  def change
+    return unless table_exists?(:active_storage_blobs)
+
+    change_column_null(:active_storage_blobs, :checksum, true)
+  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