add preprocessor to handle comment directives in sprocket 3.7.0+ , fixes #580

lib/react/rails/railtie.rb

@@ -103,9 +103,11 @@ class Railtie < ::Rails::Railtie
         if !sprockets_env.nil?
           if Gem::Version.new(Sprockets::VERSION) >= Gem::Version.new("3.7.0")
             sprockets_env.register_mime_type("application/jsx", extensions: [".jsx", ".js.jsx", ".es.jsx", ".es6.jsx"])
-            sprockets_env.register_transformer("application/jsx", "application/javascript", React::JSX::Processor)
             sprockets_env.register_mime_type("application/jsx+coffee", extensions: [".jsx.coffee", ".js.jsx.coffee"])
+            sprockets_env.register_transformer("application/jsx", "application/javascript", React::JSX::Processor)
             sprockets_env.register_transformer("application/jsx+coffee", "application/jsx", Sprockets::CoffeeScriptProcessor)
+            sprockets_env.register_preprocessor("application/jsx", Sprockets::DirectiveProcessor.new(comments: ["//", ["/*", "*/"]]))
+            sprockets_env.register_preprocessor("application/jsx+coffee", Sprockets::DirectiveProcessor.new(comments: ["#", ["###", "###"]]))
           elsif Gem::Version.new(Sprockets::VERSION) >= Gem::Version.new("3.0.0")
             sprockets_env.register_engine(".jsx", React::JSX::Processor, mime_type: "application/javascript")
           else

test/dummy/app/assets/javascripts/require_test/jsx_preprocessor_test.jsx

@@ -0,0 +1,3 @@
+//= require ./jsx_require_child_js
+<div className="le-javascript" />
+

test/dummy/app/assets/javascripts/require_test/jsx_require_child_js.jsx

@@ -0,0 +1 @@
+<div className="le-javascript-child" />

test/react/jsx/jsx_prepocessor_test.rb

@@ -0,0 +1,16 @@
+require 'test_helper'
+
+when_sprockets_available do
+  class JSXPreprocessorTest < ActionDispatch::IntegrationTest
+    EXPECTED_JS = <<javascript
+React.createElement(\"div\", { className: \"le-javascript-child\" });
+React.createElement(\"div\", { className: \"le-javascript\" });
+javascript
+
+    test 'executes //= require directives' do
+      get '/assets/require_test/jsx_preprocessor_test.js'
+      assert_response :success
+      assert_compiled_javascript_matches(@response.body, EXPECTED_JS)
+    end
+  end
+end

test/react/jsx_test.rb

@@ -66,14 +66,5 @@ def test_babel_transformer_accepts_babel_transformation_options
 
       assert !@response.body.include?('strict')
     end
-
-
-    # Different processors may generate slightly different outputs,
-    # as some version inserts an extra "\n" at the beginning.
-    # Because appraisal is used, multiple versions of coffee-script are treated
-    # together. Remove all spaces to make test pass.
-    def assert_compiled_javascript_matches(javascript, expectation)
-      assert_equal expectation.gsub(/\s/, ''), javascript.gsub(/\s/, '')
-    end
   end
 end

test/test_helper.rb

@@ -113,3 +113,14 @@ def when_sprockets_available
     yield
   end
 end
+
+class ActionDispatch::IntegrationTest
+
+# Different processors may generate slightly different outputs,
+# as some version inserts an extra "\n" at the beginning.
+# Because appraisal is used, multiple versions of coffee-script are treated
+# together. Remove all spaces to make test pass.
+  def assert_compiled_javascript_matches(javascript, expectation)
+    assert_equal expectation.gsub(/\s/, ''), javascript.gsub(/\s/, '')
+  end
+end