Load configured Active Storage plugins during boot

Previously, the parts of Active Storage using ruby-vips, mini_magick, or
image_processing would try to load gems only when used. This strategy works
well because it allows apps that don't need these features to easily
ignore them and not have to depend on gems they don't need.

However, the downsides to this strategy are that it requires loading
code during requests and that it moves potential error messages into request
logs instead of those errors being immediately visible on boot.

This commit addresses these issues by restructing how the Vips and Image
Magick transformers/analyzers are organized so that they will be loaded
(if configured) on boot along with whatever dependencies they need.

For now, if :vips or :mini_magick is specified as the Active Storage
:variant_processor, not having the required gem in the Gemfile will print a
deprecation warning instead of erroring because it is likely many apps
are currently configured this way.

activestorage/app/models/active_storage/variation.rb

@@ -82,6 +82,6 @@ def digest
 
   private
     def transformer
-      ActiveStorage::Transformers::ImageProcessingTransformer.new(transformations.except(:format))
+      ActiveStorage.variant_transformer.new(transformations.except(:format))
     end
 end

activestorage/lib/active_storage.rb

@@ -49,6 +49,8 @@ module ActiveStorage
   mattr_accessor :verifier
   mattr_accessor :variant_processor, default: :mini_magick
 
+  mattr_accessor :variant_transformer
+
   mattr_accessor :queues, default: {}
 
   mattr_accessor :previewers, default: []
@@ -379,5 +381,7 @@ module Transformers
 
     autoload :Transformer
     autoload :ImageProcessingTransformer
+    autoload :Vips
+    autoload :ImageMagick
   end
 end

activestorage/lib/active_storage/analyzer/image_analyzer.rb

@@ -12,6 +12,11 @@ module ActiveStorage
   #   ActiveStorage::Analyzer::ImageAnalyzer::ImageMagick.new(blob).metadata
   #   # => { width: 4104, height: 2736 }
   class Analyzer::ImageAnalyzer < Analyzer
+    extend ActiveSupport::Autoload
+
+    autoload :Vips
+    autoload :ImageMagick
+
     def self.accept?(blob)
       blob.image?
     end

activestorage/lib/active_storage/analyzer/image_analyzer/image_magick.rb

@@ -1,22 +1,17 @@
 # frozen_string_literal: true
 
+begin
+  gem "mini_magick"
+rescue LoadError => error
+  raise error unless error.message.match?(/ruby-vips/)
+end
+
 module ActiveStorage
   # This analyzer relies on the third-party {MiniMagick}[https://github.com/minimagick/minimagick] gem. MiniMagick requires
   # the {ImageMagick}[http://www.imagemagick.org] system library.
   class Analyzer::ImageAnalyzer::ImageMagick < Analyzer::ImageAnalyzer
-    def self.accept?(blob)
-      super && ActiveStorage.variant_processor == :mini_magick
-    end
-
     private
       def read_image
-        begin
-          require "mini_magick"
-        rescue LoadError
-          logger.info "Skipping image analysis because the mini_magick gem isn't installed"
-          return {}
-        end
-
         download_blob_to_tempfile do |file|
           image = instrument("mini_magick") do
             MiniMagick::Image.new(file.path)

activestorage/lib/active_storage/analyzer/image_analyzer/vips.rb

@@ -1,22 +1,18 @@
 # frozen_string_literal: true
 
+begin
+  gem "ruby-vips"
+  require "ruby-vips"
+rescue LoadError => error
+  raise error unless error.message.match?(/ruby-vips/)
+end
+
 module ActiveStorage
   # This analyzer relies on the third-party {ruby-vips}[https://github.com/libvips/ruby-vips] gem. Ruby-vips requires
   # the {libvips}[https://libvips.github.io/libvips/] system library.
   class Analyzer::ImageAnalyzer::Vips < Analyzer::ImageAnalyzer
-    def self.accept?(blob)
-      super && ActiveStorage.variant_processor == :vips
-    end
-
     private
       def read_image
-        begin
-          require "ruby-vips"
-        rescue LoadError
-          logger.info "Skipping image analysis because the ruby-vips gem isn't installed"
-          return {}
-        end
-
         download_blob_to_tempfile do |file|
           image = instrument("vips") do
             # ruby-vips will raise Vips::Error if it can't find an appropriate loader for the file
@@ -35,6 +31,9 @@ def read_image
           logger.error "Skipping image analysis due to a Vips error: #{error.message}"
           {}
         end
+      rescue ::Vips::Error => error
+        logger.error "Skipping image analysis due to an Vips error: #{error.message}"
+        {}
       end
 
       ROTATIONS = /Right-top|Left-bottom|Top-right|Bottom-left/

activestorage/lib/active_storage/engine.rb

@@ -12,8 +12,6 @@
 require "active_storage/previewer/video_previewer"
 
 require "active_storage/analyzer/image_analyzer"
-require "active_storage/analyzer/image_analyzer/image_magick"
-require "active_storage/analyzer/image_analyzer/vips"
 require "active_storage/analyzer/video_analyzer"
 require "active_storage/analyzer/audio_analyzer"
 
@@ -27,7 +25,7 @@ class Engine < Rails::Engine # :nodoc:
 
     config.active_storage = ActiveSupport::OrderedOptions.new
     config.active_storage.previewers = [ ActiveStorage::Previewer::PopplerPDFPreviewer, ActiveStorage::Previewer::MuPDFPreviewer, ActiveStorage::Previewer::VideoPreviewer ]
-    config.active_storage.analyzers = [ ActiveStorage::Analyzer::ImageAnalyzer::Vips, ActiveStorage::Analyzer::ImageAnalyzer::ImageMagick, ActiveStorage::Analyzer::VideoAnalyzer, ActiveStorage::Analyzer::AudioAnalyzer ]
+    config.active_storage.analyzers = [ ActiveStorage::Analyzer::VideoAnalyzer, ActiveStorage::Analyzer::AudioAnalyzer ]
     config.active_storage.paths = ActiveSupport::OrderedOptions.new
     config.active_storage.queues = ActiveSupport::InheritableOptions.new
     config.active_storage.precompile_assets = true
@@ -86,9 +84,43 @@ class Engine < Rails::Engine # :nodoc:
     initializer "active_storage.configs" do
       config.after_initialize do |app|
         ActiveStorage.logger            = app.config.active_storage.logger || Rails.logger
-        ActiveStorage.variant_processor = app.config.active_storage.variant_processor || :mini_magick
+        ActiveStorage.variant_processor = app.config.active_storage.variant_processor
         ActiveStorage.previewers        = app.config.active_storage.previewers || []
-        ActiveStorage.analyzers         = app.config.active_storage.analyzers || []
+
+        begin
+          analyzer, transformer =
+            case ActiveStorage.variant_processor
+            when :vips
+              [
+                ActiveStorage::Analyzer::ImageAnalyzer::Vips,
+                ActiveStorage::Transformers::Vips
+              ]
+            when :mini_magick
+              [
+                ActiveStorage::Analyzer::ImageAnalyzer::ImageMagick,
+                ActiveStorage::Transformers::ImageMagick
+              ]
+            end
+
+          ActiveStorage.analyzers = [analyzer].concat(app.config.active_storage.analyzers || [])
+          ActiveStorage.variant_transformer = transformer
+        rescue LoadError => error
+          case error.message
+          when /libvips/
+            ActiveStorage.logger.warn <<~WARNING.squish
+              Using vips to process variants requires the libvips library.
+              Please install libvips using the instructions on the libvips website.
+            WARNING
+          when /image_processing/
+            ActiveStorage.logger.warn <<~WARNING.squish
+              Generating image variants require the image_processing gem.
+              Please add `gem 'image_processing', '~> 1.2'` to your Gemfile.
+            WARNING
+          else
+            raise
+          end
+        end
+
         ActiveStorage.paths             = app.config.active_storage.paths || {}
         ActiveStorage.routes_prefix     = app.config.active_storage.routes_prefix || "/rails/active_storage"
         ActiveStorage.draw_routes       = app.config.active_storage.draw_routes != false

activestorage/lib/active_storage/transformers/image_magick.rb

@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  module Transformers
+    class ImageMagick < ImageProcessingTransformer
+      private
+        def processor
+          ImageProcessing::MiniMagick
+        end
+
+        def validate_transformation(name, argument)
+          method_name = name.to_s.tr("-", "_")
+
+          unless ActiveStorage.supported_image_processing_methods.include?(method_name)
+            raise UnsupportedImageProcessingMethod, <<~ERROR.squish
+              The provided transformation method is not supported: #{method_name}.
+            ERROR
+          end
+
+          if argument.present?
+            if argument.is_a?(String) || argument.is_a?(Symbol)
+              validate_arg_string(argument)
+            elsif argument.is_a?(Array)
+              validate_arg_array(argument)
+            elsif argument.is_a?(Hash)
+              validate_arg_hash(argument)
+            end
+          end
+
+          super
+        end
+
+        def validate_arg_string(argument)
+          unsupported_arguments = ActiveStorage.unsupported_image_processing_arguments.any? do |bad_arg|
+            argument.to_s.downcase.include?(bad_arg)
+          end
+
+          raise UnsupportedImageProcessingArgument if unsupported_arguments
+        end
+
+        def validate_arg_array(argument)
+          argument.each do |arg|
+            if arg.is_a?(Integer) || arg.is_a?(Float)
+              next
+            elsif arg.is_a?(String) || arg.is_a?(Symbol)
+              validate_arg_string(arg)
+            elsif arg.is_a?(Array)
+              validate_arg_array(arg)
+            elsif arg.is_a?(Hash)
+              validate_arg_hash(arg)
+            end
+          end
+        end
+
+        def validate_arg_hash(argument)
+          argument.each do |key, value|
+            validate_arg_string(key)
+
+            if value.is_a?(Integer) || value.is_a?(Float)
+              next
+            elsif value.is_a?(String) || value.is_a?(Symbol)
+              validate_arg_string(value)
+            elsif value.is_a?(Array)
+              validate_arg_array(value)
+            elsif value.is_a?(Hash)
+              validate_arg_hash(value)
+            end
+          end
+        end
+    end
+  end
+end

activestorage/lib/active_storage/transformers/image_processing_transformer.rb

@@ -25,22 +25,9 @@ def process(file, format:)
             call
         end
 
-        def processor
-          ImageProcessing.const_get(ActiveStorage.variant_processor.to_s.camelize)
-        end
-
         def operations
           transformations.each_with_object([]) do |(name, argument), list|
-            if ActiveStorage.variant_processor == :mini_magick
-              validate_transformation(name, argument)
-            end
-
-            if name.to_s == "combine_options"
-              raise ArgumentError, <<~ERROR.squish
-                Active Storage's ImageProcessing transformer doesn't support :combine_options,
-                as it always generates a single command.
-              ERROR
-            end
+            validate_transformation(name, argument)
 
             if argument.present?
               list << [ name, argument ]
@@ -49,61 +36,12 @@ def operations
         end
 
         def validate_transformation(name, argument)
-          method_name = name.to_s.tr("-", "_")
-
-          unless ActiveStorage.supported_image_processing_methods.any? { |method| method_name == method }
-            raise UnsupportedImageProcessingMethod, <<~ERROR.squish
-              One or more of the provided transformation methods is not supported.
+          if name.to_s == "combine_options"
+            raise ArgumentError, <<~ERROR.squish
+              Active Storage's ImageProcessing transformer doesn't support :combine_options,
+              as it always generates a single command.
             ERROR
           end
-
-          if argument.present?
-            if argument.is_a?(String) || argument.is_a?(Symbol)
-              validate_arg_string(argument)
-            elsif argument.is_a?(Array)
-              validate_arg_array(argument)
-            elsif argument.is_a?(Hash)
-              validate_arg_hash(argument)
-            end
-          end
-        end
-
-        def validate_arg_string(argument)
-          unsupported_arguments = ActiveStorage.unsupported_image_processing_arguments.any? do |bad_arg|
-            argument.to_s.downcase.include?(bad_arg)
-          end
-
-          raise UnsupportedImageProcessingArgument if unsupported_arguments
-        end
-
-        def validate_arg_array(argument)
-          argument.each do |arg|
-            if arg.is_a?(Integer) || arg.is_a?(Float)
-              next
-            elsif arg.is_a?(String) || arg.is_a?(Symbol)
-              validate_arg_string(arg)
-            elsif arg.is_a?(Array)
-              validate_arg_array(arg)
-            elsif arg.is_a?(Hash)
-              validate_arg_hash(arg)
-            end
-          end
-        end
-
-        def validate_arg_hash(argument)
-          argument.each do |key, value|
-            validate_arg_string(key)
-
-            if value.is_a?(Integer) || value.is_a?(Float)
-              next
-            elsif value.is_a?(String) || value.is_a?(Symbol)
-              validate_arg_string(value)
-            elsif value.is_a?(Array)
-              validate_arg_array(value)
-            elsif value.is_a?(Hash)
-              validate_arg_hash(value)
-            end
-          end
         end
     end
   end

activestorage/lib/active_storage/transformers/vips.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  module Transformers
+    class Vips < ImageProcessingTransformer
+      def processor
+        ImageProcessing::Vips
+      end
+    end
+  end
+end

activestorage/test/analyzer/image_analyzer/image_magick_test.rb

@@ -60,13 +60,12 @@ class ActiveStorage::Analyzer::ImageAnalyzer::ImageMagickTest < ActiveSupport::T
 
   private
     def analyze_with_image_magick
-      previous_processor, ActiveStorage.variant_processor = ActiveStorage.variant_processor, :mini_magick
-      require "mini_magick"
+      previous_analyzers, ActiveStorage.analyzers = ActiveStorage.analyzers, [ActiveStorage::Analyzer::ImageAnalyzer::ImageMagick]
 
       yield
     rescue LoadError
       ENV["BUILDKITE"] ? raise : skip("Variant processor image_magick is not installed")
     ensure
-      ActiveStorage.variant_processor = previous_processor
+      ActiveStorage.analyzers = previous_analyzers
     end
 end

activestorage/test/analyzer/image_analyzer/vips_test.rb

@@ -60,13 +60,12 @@ class ActiveStorage::Analyzer::ImageAnalyzer::VipsTest < ActiveSupport::TestCase
 
   private
     def analyze_with_vips
-      previous_processor, ActiveStorage.variant_processor = ActiveStorage.variant_processor, :vips
-      require "ruby-vips"
+      previous_analyzers, ActiveStorage.analyzers = ActiveStorage.analyzers, [ActiveStorage::Analyzer::ImageAnalyzer::Vips]
 
       yield
     rescue LoadError
       ENV["BUILDKITE"] ? raise : skip("Variant processor vips is not installed")
     ensure
-      ActiveStorage.variant_processor = previous_processor
+      ActiveStorage.analyzers = previous_analyzers
     end
 end