Fix/issue 1889 (#1892)

* Add regression test for infinite loop issue in Util::step_through_extensions (#1889)

* Prevent infinite loop when encountering files where base filename is a possible templating engine

middleman-core/lib/middleman-core/util/files.rb

@@ -58,6 +58,8 @@ module Middleman
     def step_through_extensions(path)
       while ::Middleman::Util.tilt_class(path)
         ext = ::File.extname(path)
+        break if ext.empty?
+
         yield ext if block_given?
 
         # Strip templating extensions as long as Tilt knows them

middleman-core/spec/middleman-core/util_spec.rb

@@ -204,4 +204,20 @@ describe Middleman::Util do
       expect(related).to include File.expand_path("source/stylesheets/include2.css.scss")
     end
   end
+
+  describe "::step_through_extensions" do
+    it "returns the base name after templating engine extensions are removed" do
+      result = Middleman::Util.step_through_extensions('my_file.html.haml.erb')
+      expect(result).to eq 'my_file.html'
+    end
+
+    it "does not loop infinitely when file name is a possible templating engine" do
+      expect do
+        Timeout::timeout(0.5) do
+          result = Middleman::Util.step_through_extensions("markdown.scss")
+          expect(result).to eq "markdown"
+        end
+      end.not_to raise_error
+    end
+  end
 end