Change asset finder configuration

This commit changes the way the asset finder is configured. Instead of setting
the asset finder from an initializer to a specific class, the asset finder is
now detected unless configured otherwise.

This allows InlineSvg to work with Sprockets, Propshaft, or a fallback static
asset finder without any configuration.

lib/inline_svg.rb

@@ -4,6 +4,7 @@
 require "inline_svg/cached_asset_file"
 require "inline_svg/finds_asset_paths"
 require "inline_svg/propshaft_asset_finder"
+require "inline_svg/sprockets_asset_finder"
 require "inline_svg/static_asset_finder"
 require "inline_svg/webpack_asset_finder"
 require "inline_svg/transform_pipeline"
@@ -19,7 +20,15 @@ module InlineSvg
   class Configuration
     class Invalid < ArgumentError; end
 
-    attr_reader :asset_file, :asset_finder, :custom_transformations, :svg_not_found_css_class
+    attr_reader :asset_file, :custom_transformations, :svg_not_found_css_class
+
+    # Asset finders are ordered by priority. Unless configured otherwise, the
+    # first asset finder that matches will be used.
+    ASSET_FINDERS = [
+      InlineSvg::SprocketsAssetFinder,
+      InlineSvg::PropshaftAssetFinder,
+      InlineSvg::StaticAssetFinder
+    ].freeze
 
     def initialize
       @custom_transformations = {}
@@ -41,18 +50,16 @@ def asset_file=(custom_asset_file)
       end
     end
 
-    def asset_finder=(finder)
-      @asset_finder = if finder.respond_to?(:find_asset)
-                        finder
-                      elsif finder.class.name == "Propshaft::Assembly"
-                        InlineSvg::PropshaftAssetFinder
-                      else
-                        # fallback to a naive static asset finder
-                        # (sprokects >= 3.0 && config.assets.precompile = false
-                        # See: https://github.com/jamesmartin/inline_svg/issues/25
-                        InlineSvg::StaticAssetFinder
-                      end
-      asset_finder
+    def asset_finder=(asset_finder)
+      if asset_finder.respond_to?(:find_asset)
+        @asset_finder = asset_finder
+      else
+        raise InlineSvg::Configuration::Invalid.new("asset_finder should implement the #find_asset method")
+      end
+    end
+
+    def asset_finder
+      @asset_finder ||= matching_asset_finder
     end
 
     def svg_not_found_css_class=(css_class)
@@ -68,9 +75,7 @@ def add_custom_transformation(options)
       @custom_transformations.merge!(Hash[ *[options.fetch(:attribute, :no_attribute), options] ])
     end
 
-    def raise_on_file_not_found=(value)
-      @raise_on_file_not_found = value
-    end
+    attr_writer :raise_on_file_not_found
 
     def raise_on_file_not_found?
       !!@raise_on_file_not_found
@@ -82,6 +87,9 @@ def incompatible_transformation?(klass)
       !klass.is_a?(Class) || !klass.respond_to?(:create_with_value) || !klass.instance_methods.include?(:transform)
     end
 
+    def matching_asset_finder
+      ASSET_FINDERS.detect(&:match?)
+    end
   end
 
   @configuration = InlineSvg::Configuration.new

lib/inline_svg/propshaft_asset_finder.rb

@@ -1,16 +1,25 @@
 module InlineSvg
   class PropshaftAssetFinder
+    def self.assets
+      Rails.application.assets
+    end
+
     def self.find_asset(filename)
       new(filename)
     end
 
+    def self.match?
+      assets.instance_of?(Propshaft::Assembly)
+    rescue NameError
+    end
+
     def initialize(filename)
       @filename = filename
     end
 
     def pathname
-      asset_path = ::Rails.application.assets.load_path.find(@filename)
-      asset_path.path unless asset_path.nil?
+      asset_path = self.class.assets.load_path.find(@filename)
+      asset_path&.path
     end
   end
 end

lib/inline_svg/railtie.rb

@@ -7,18 +7,5 @@ class Railtie < ::Rails::Railtie
         include InlineSvg::ActionView::Helpers
       end
     end
-
-    config.after_initialize do |app|
-      InlineSvg.configure do |config|
-        # Configure the asset_finder:
-        # Only set this when a user-configured asset finder has not been
-        # configured already.
-        if config.asset_finder.nil?
-          # In default Rails apps, this will be a fully operational
-          # Sprockets::Environment instance
-          config.asset_finder = app.instance_variable_get(:@assets)
-        end
-      end
-    end
   end
 end

lib/inline_svg/sprockets_asset_finder.rb

@@ -0,0 +1,16 @@
+module InlineSvg
+  module SprocketsAssetFinder
+    def self.assets
+      Rails.application.assets
+    end
+
+    def self.find_asset(*args, **options)
+      assets.find_asset(*args, **options)
+    end
+
+    def self.match?
+      assets.respond_to?(:find_asset)
+    rescue NameError
+    end
+  end
+end

lib/inline_svg/static_asset_finder.rb

@@ -10,6 +10,10 @@ def self.find_asset(filename)
       new(filename)
     end
 
+    def self.match?
+      true
+    end
+
     def initialize(filename)
       @filename = filename
     end

lib/inline_svg/webpack_asset_finder.rb

@@ -7,7 +7,7 @@ def self.find_asset(filename)
     def initialize(filename)
       @filename = filename
       manifest_lookup = Webpacker.manifest.lookup(@filename)
-      @asset_path =  manifest_lookup.present? ? URI(manifest_lookup).path : ""
+      @asset_path = manifest_lookup.present? ? URI(manifest_lookup).path : ""
     end
 
     def pathname
@@ -31,7 +31,7 @@ def dev_server_asset(file_path)
           file.write(asset)
           file.rewind
         end
-      rescue StandardError => e
+      rescue => e
         Rails.logger.error "[inline_svg] Error creating tempfile for #{@filename}: #{e}"
         raise
       end
@@ -43,7 +43,7 @@ def fetch_from_dev_server(file_path)
       http.verify_mode = OpenSSL::SSL::VERIFY_NONE
 
       http.request(Net::HTTP::Get.new(file_path)).body
-    rescue StandardError => e
+    rescue => e
       Rails.logger.error "[inline_svg] Error fetching #{@filename} from webpack-dev-server: #{e}"
       raise
     end

spec/inline_svg_spec.rb

@@ -28,21 +28,51 @@ def self.named(filename); end
     end
 
     context "asset finder" do
-      it "allows an asset finder to be assigned" do
-        sprockets = double('SomethingLikeSprockets', find_asset: 'some asset')
-        InlineSvg.configure do |config|
-          config.asset_finder = sprockets
+      context "when Sprockets is detected" do
+        it "uses the Sprockets asset finder" do
+          sprockets = double("Sprockets", find_asset: "some asset")
+          stub_const("Rails", double("Rails"))
+          allow(Rails).to receive_message_chain(:application, :assets).and_return(sprockets)
+
+          expect(InlineSvg.configuration.asset_finder).to eq InlineSvg::SprocketsAssetFinder
         end
+      end
+
+      context "when Propshaft is detected" do
+        it "uses the Propshaft asset finder" do
+          stub_const("Propshaft::Assembly", Class.new)
+          stub_const("Rails", double("Rails"))
+          allow(Rails).to receive_message_chain(:application, :assets).and_return(Propshaft::Assembly.new)
 
-        expect(InlineSvg.configuration.asset_finder).to eq sprockets
+          expect(InlineSvg.configuration.asset_finder).to eq InlineSvg::PropshaftAssetFinder
+        end
+      end
+
+      context "when Sprockets and Propshaft are not detected" do
+        it "uses the static asset finder" do
+          expect(InlineSvg.configuration.asset_finder).to eq InlineSvg::StaticAssetFinder
+        end
       end
 
-      it "falls back to StaticAssetFinder when the provided asset finder does not implement #find_asset" do
+      it "allows an asset finder to be assigned" do
+        asset_finder = double("An asset finder", find_asset: "some asset")
         InlineSvg.configure do |config|
-          config.asset_finder = 'Not a real asset finder'
+          config.asset_finder = asset_finder
         end
 
-        expect(InlineSvg.configuration.asset_finder).to eq InlineSvg::StaticAssetFinder
+        expect(InlineSvg.configuration.asset_finder).to eq asset_finder
+      end
+
+      it "raises an error if the asset finder does not implement the find_asset method" do
+        expect {
+          InlineSvg.configure do |config|
+            config.asset_finder = "Not a real asset finder"
+          end
+        }.to raise_error(InlineSvg::Configuration::Invalid, /asset_finder should implement the #find_asset method/)
+      end
+
+      after do
+        InlineSvg.reset_configuration!
       end
     end
 
@@ -122,7 +152,6 @@ def self.named(filename); end
           end
         end.to raise_error(InlineSvg::Configuration::Invalid, /#{:not_a_class} should implement the .create_with_value and #transform methods/)
       end
-
     end
   end
 end

spec/sprockets_asset_finder_spec.rb

@@ -0,0 +1,11 @@
+require_relative "../lib/inline_svg"
+
+describe InlineSvg::SprocketsAssetFinder do
+  it "returns assets from Sprockets" do
+    sprockets = double("Sprockets", find_asset: "some asset")
+    stub_const("Rails", double("Rails"))
+    allow(Rails).to receive_message_chain(:application, :assets).and_return(sprockets)
+
+    expect(described_class.find_asset("some-file")).to eq "some asset"
+  end
+end