[ActiveStorage] Add ability to use pre-defined variants

activestorage/CHANGELOG.md

@@ -1,3 +1,25 @@
+*   Add ability to use pre-defined variants.
+
+    ```ruby
+    class User < ActiveRecord::Base
+      has_one_attached :avatar, variants: {
+        thumb: { resize: "100x100" },
+        medium: { resize: "300x300", monochrome: true }
+      }
+    end
+
+    class Gallery < ActiveRecord::Base
+      has_many_attached :photos, variants: {
+        thumb: { resize: "100x100" },
+        medium: { resize: "300x300", monochrome: true }
+      }
+    end
+
+    <%= image_tag user.avatar.variant(:thumb) %>
+    ```
+
+    *fatkodima*
+
 *   Add `config.active_storage.web_image_content_types` to allow applications
     to add content types (like `image/webp`) in which variants can be processed,
     instead of letting those images be converted to the fallback PNG format.

activestorage/app/models/active_storage/attachment.rb

@@ -30,6 +30,19 @@ class ActiveStorage::Attachment < ActiveRecord::Base
     blob&.purge_later
   end
 
+  def variant(transformations)
+    case transformations
+    when Symbol
+      variant_name = transformations
+      transformations = variants.fetch(variant_name) do
+        record_model_name = record.to_model.model_name.name
+        raise ArgumentError, "Cannot find variant :#{variant_name} for #{record_model_name}##{name}"
+      end
+    end
+
+    blob.variant(transformations)
+  end
+
   private
     def identify_blob
       blob.identify
@@ -51,6 +64,10 @@ class ActiveStorage::Attachment < ActiveRecord::Base
     def dependent
       record.attachment_reflections[name]&.options[:dependent]
     end
+
+    def variants
+      record.attachment_reflections[name]&.options[:variants]
+    end
 end
 
 ActiveSupport.run_load_hooks :active_storage_attachment, ActiveStorage::Attachment

activestorage/lib/active_storage/attached/model.rb

@@ -40,7 +40,7 @@ module ActiveStorage
       #     has_one_attached :avatar, service: :s3
       #   end
       #
-      def has_one_attached(name, dependent: :purge_later, service: nil)
+      def has_one_attached(name, dependent: :purge_later, service: nil, variants: {})
         validate_service_configuration(name, service)
 
         generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
@@ -72,7 +72,7 @@ module ActiveStorage
           :has_one_attached,
           name,
           nil,
-          { dependent: dependent, service_name: service },
+          { dependent: dependent, service_name: service, variants: variants },
           self
         )
         ActiveRecord::Reflection.add_attachment_reflection(self, name, reflection)
@@ -110,7 +110,7 @@ module ActiveStorage
       #     has_many_attached :photos, service: :s3
       #   end
       #
-      def has_many_attached(name, dependent: :purge_later, service: nil)
+      def has_many_attached(name, dependent: :purge_later, service: nil, variants: {})
         validate_service_configuration(name, service)
 
         generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
@@ -159,7 +159,7 @@ module ActiveStorage
           :has_many_attached,
           name,
           nil,
-          { dependent: dependent, service_name: service },
+          { dependent: dependent, service_name: service, variants: variants },
           self
         )
         ActiveRecord::Reflection.add_attachment_reflection(self, name, reflection)

activestorage/test/models/attached/many_test.rb

@@ -610,6 +610,26 @@ class ActiveStorage::ManyAttachedTest < ActiveSupport::TestCase
     assert_match(/Cannot configure service :unknown for User#featured_photos/, error.message)
   end
 
+  test "creating variation by variation name" do
+    @user.highlights_with_variants.attach fixture_file_upload("racecar.jpg")
+    variant = @user.highlights_with_variants.first.variant(:thumb).processed
+
+    image = read_image(variant)
+    assert_equal "JPEG", image.type
+    assert_equal 100, image.width
+    assert_equal 67, image.height
+  end
+
+  test "raises error when unknown variant name is used" do
+    @user.highlights_with_variants.attach fixture_file_upload("racecar.jpg")
+
+    error = assert_raises ArgumentError do
+      @user.highlights_with_variants.first.variant(:unknown).processed
+    end
+
+    assert_match(/Cannot find variant :unknown for User#highlights_with_variants/, error.message)
+  end
+
   private
     def append_on_assign
       ActiveStorage.replace_on_assign_to_many, previous = false, ActiveStorage.replace_on_assign_to_many

activestorage/test/models/attached/one_test.rb

@@ -584,4 +584,24 @@ class ActiveStorage::OneAttachedTest < ActiveSupport::TestCase
 
     assert_match(/Cannot configure service :unknown for User#featured_photo/, error.message)
   end
+
+  test "creating variation by variation name" do
+    @user.avatar_with_variants.attach fixture_file_upload("racecar.jpg")
+    variant = @user.avatar_with_variants.variant(:thumb).processed
+
+    image = read_image(variant)
+    assert_equal "JPEG", image.type
+    assert_equal 100, image.width
+    assert_equal 67, image.height
+  end
+
+  test "raises error when unknown variant name is used" do
+    @user.avatar_with_variants.attach fixture_file_upload("racecar.jpg")
+
+    error = assert_raises ArgumentError do
+      @user.avatar_with_variants.variant(:unknown).processed
+    end
+
+    assert_match(/Cannot find variant :unknown for User#avatar_with_variants/, error.message)
+  end
 end

activestorage/test/models/reflection_test.rb

@@ -12,6 +12,9 @@ class ActiveStorage::ReflectionTest < ActiveSupport::TestCase
 
     reflection = User.reflect_on_attachment(:cover_photo)
     assert_equal :local, reflection.options[:service_name]
+
+    reflection = User.reflect_on_attachment(:avatar_with_variants)
+    assert_instance_of Hash, reflection.options[:variants]
   end
 
   test "reflection on a singular attachment with the same name as an attachment on another model" do
@@ -28,13 +31,16 @@ class ActiveStorage::ReflectionTest < ActiveSupport::TestCase
 
     reflection = User.reflect_on_attachment(:vlogs)
     assert_equal :local, reflection.options[:service_name]
+
+    reflection = User.reflect_on_attachment(:highlights_with_variants)
+    assert_instance_of Hash, reflection.options[:variants]
   end
 
   test "reflecting on all attachments" do
     reflections = User.reflect_on_all_attachments.sort_by(&:name)
     assert_equal [ User ], reflections.collect(&:active_record).uniq
-    assert_equal %i[ avatar cover_photo highlights vlogs ], reflections.collect(&:name)
-    assert_equal %i[ has_one_attached has_one_attached has_many_attached has_many_attached ], reflections.collect(&:macro)
-    assert_equal [ :purge_later, false, :purge_later, false ], reflections.collect { |reflection| reflection.options[:dependent] }
+    assert_equal %i[ avatar avatar_with_variants cover_photo highlights highlights_with_variants vlogs ], reflections.collect(&:name)
+    assert_equal %i[ has_one_attached has_one_attached has_one_attached has_many_attached has_many_attached has_many_attached ], reflections.collect(&:macro)
+    assert_equal [ :purge_later, :purge_later, false, :purge_later, :purge_later, false ], reflections.collect { |reflection| reflection.options[:dependent] }
   end
 end

activestorage/test/test_helper.rb

@@ -119,9 +119,11 @@ class User < ActiveRecord::Base
 
   has_one_attached :avatar
   has_one_attached :cover_photo, dependent: false, service: :local
+  has_one_attached :avatar_with_variants, variants: { thumb: { resize: "100x100" } }
 
   has_many_attached :highlights
   has_many_attached :vlogs, dependent: false, service: :local
+  has_many_attached :highlights_with_variants, variants: { thumb: { resize: "100x100" } }
 end
 
 class Group < ActiveRecord::Base

guides/source/active_storage_overview.md

@@ -129,7 +129,7 @@ amazon:
   secret_access_key: ""
   region: ""
   bucket: ""
-  upload: 
+  upload:
     server_side_encryption: "" # 'aws:kms' or 'AES256'
 ```
 
@@ -332,6 +332,20 @@ class User < ApplicationRecord
 end
 ```
 
+You can configure specific variants per attachment using the `variants` option:
+
+```ruby
+class User < ApplicationRecord
+  has_one_attached :avatar, variants: { thumb: { resize: "100x100" } }
+end
+```
+
+Call `avatar.variant(:thumb)` to get a thumb variant of an avatar:
+
+```ruby
+<%= image_tag user.avatar.variant(:thumb) %>
+```
+
 ### `has_many_attached`
 
 The `has_many_attached` macro sets up a one-to-many relationship between records
@@ -382,6 +396,14 @@ class Message < ApplicationRecord
 end
 ```
 
+Configuring specific variants is done the same way as `has_one_attached`, by using the `variants` option:
+
+```ruby
+class Message < ApplicationRecord
+  has_many_attached :images, variants: { thumb: { resize: "100x100" } }
+end
+```
+
 ### Attaching File/IO Objects
 
 Sometimes you need to attach a file that doesn’t arrive via an HTTP request.