Allow webp as image file format

app/models/alchemy/picture.rb

@@ -28,7 +28,7 @@ class Picture < BaseRecord
       large: "240x180",
     }.with_indifferent_access.freeze
 
-    CONVERTIBLE_FILE_FORMATS = %w(gif jpg jpeg png).freeze
+    CONVERTIBLE_FILE_FORMATS = %w[gif jpg jpeg png webp].freeze
 
     TRANSFORMATION_OPTIONS = [
       :crop,

config/alchemy/config.yml

@@ -173,6 +173,7 @@ uploader:
     - gif
     - png
     - svg
+    - webp
 
 # === Link Target Options
 #

lib/alchemy/engine.rb

@@ -45,5 +45,16 @@ class Engine < Rails::Engine
         end
       end
     end
+
+    initializer "alchemy.webp-mime_type" do
+      # Rails does not know anything about webp even in 2022
+      unless Mime::Type.lookup_by_extension(:webp)
+        Mime::Type.register("image/webp", :webp)
+      end
+      # Dragonfly uses Rack to read the mime type and guess what
+      unless Rack::Mime::MIME_TYPES[".webp"]
+        Rack::Mime::MIME_TYPES[".webp"] = "image/webp"
+      end
+    end
   end
 end

spec/models/alchemy/picture_spec.rb

@@ -34,6 +34,18 @@ module Alchemy
       end
     end
 
+    context "with a webp file" do
+      let :image_file do
+        File.new(File.expand_path("../../fixtures/image5.webp", __dir__))
+      end
+
+      it "generates thumbnails after create" do
+        expect {
+          create(:alchemy_picture)
+        }.to change { Alchemy::PictureThumb.count }.by(3)
+      end
+    end
+
     it "is valid with valid attributes" do
       picture = Picture.new(image_file: image_file)
       expect(picture).to be_valid
@@ -385,7 +397,7 @@ module Alchemy
         end
       end
 
-      context "when `image_output_format` is configured to an image format" do
+      context "when `image_output_format` is configured to jpg" do
         before do
           stub_alchemy_config(:image_output_format, "jpg")
         end
@@ -406,6 +418,28 @@ module Alchemy
           end
         end
       end
+
+      context "when `image_output_format` is configured to webp" do
+        before do
+          stub_alchemy_config(:image_output_format, "webp")
+        end
+
+        context "and the format is a convertible format" do
+          it "returns the configured file format." do
+            is_expected.to eq("webp")
+          end
+        end
+
+        context "but the format is not a convertible format" do
+          before do
+            allow(picture).to receive(:image_file_format) { "svg" }
+          end
+
+          it "returns the original file format." do
+            is_expected.to eq("svg")
+          end
+        end
+      end
     end
 
     describe "after update" do