Abstract svg read & placeholder logic

Refactor placeholder method

Test

Re: jamesmartin#73

lib/inline_svg/action_view/helpers.rb

@@ -6,16 +6,16 @@ module ActionView
     module Helpers
       def inline_svg(filename, transform_params={})
         begin
-          svg_file = if InlineSvg::IOResource === filename
-            InlineSvg::IOResource.read filename
-          else
-            configured_asset_file.named filename
-          end
+          svg_file = read_svg(filename)
         rescue InlineSvg::AssetFile::FileNotFound
-          if InlineSvg.configuration.svg_not_found_css_class.nil?
-            return "<svg><!-- SVG file not found: '#{filename}' #{extension_hint(filename)}--></svg>".html_safe
-          else
-            return "<svg class='#{InlineSvg.configuration.svg_not_found_css_class}'><!-- SVG file not found: '#{filename}' #{extension_hint(filename)}--></svg>".html_safe
+          return placeholder(filename) unless transform_params[:fallback].present?
+
+          if transform_params[:fallback].present?
+            begin
+              svg_file = read_svg(transform_params[:fallback])
+            rescue InlineSvg::AssetFile::FileNotFound
+              placeholder(filename)
+            end
           end
         end
 
@@ -24,6 +24,25 @@ def inline_svg(filename, transform_params={})
 
       private
 
+      def read_svg(filename)
+        if InlineSvg::IOResource === filename
+          InlineSvg::IOResource.read filename
+        else
+          configured_asset_file.named filename
+        end
+      end
+
+      def placeholder(filename)
+        css_class = InlineSvg.configuration.svg_not_found_css_class
+        not_found_message = "'#{filename}' #{extension_hint(filename)}"
+
+        if css_class.nil?
+          return "<svg><!-- SVG file not found: #{not_found_message}--></svg>".html_safe
+        else
+          return "<svg class='#{css_class}'><!-- SVG file not found: #{not_found_message}--></svg>".html_safe
+        end
+      end
+
       def configured_asset_file
         InlineSvg.configuration.asset_file
       end

spec/helpers/inline_svg_spec.rb

@@ -52,6 +52,20 @@ def transform(doc)
         expect(output).to eq "<svg class='missing-svg'><!-- SVG file not found: 'some-other-missing-file.svg' --></svg>"
         expect(output).to be_html_safe
       end
+
+      context "and a fallback that does exist" do
+        it "displays the fallback" do
+          allow(InlineSvg::AssetFile).to receive(:named).
+            with('missing.svg').
+            and_raise(InlineSvg::AssetFile::FileNotFound.new)
+
+          fallback_file = <<-SVG
+<svg xmlns="http://www.w3.org/2000/svg" xml:lang="en"><!-- This is a comment --></svg>
+SVG
+          allow(InlineSvg::AssetFile).to receive(:named).with('fallback.svg').and_return(fallback_file)
+          expect(helper.inline_svg('missing.svg', fallback: 'fallback.svg')).to eq fallback_file
+        end
+      end
     end
 
     context "when passed an existing SVG file" do