fix(bundle): Rollup: Do not warn on THIS_IS_UNDEFINED

Author: christopherthielen

rollup.config.js

@@ -4,23 +4,31 @@ import progress from 'rollup-plugin-progress';
 import sourcemaps from 'rollup-plugin-sourcemaps';
 import visualizer from 'rollup-plugin-visualizer';
 
-var MINIFY = process.env.MINIFY;
+const MINIFY = process.env.MINIFY;
 
-var pkg = require('./package.json');
-var banner =
+const pkg = require('./package.json');
+const banner =
 `/**
  * ${pkg.description}
  * @version v${pkg.version}
  * @link ${pkg.homepage}
  * @license MIT License, http://www.opensource.org/licenses/MIT
  */`;
 
-var uglifyOpts = { output: {} };
+const uglifyOpts = { output: {} };
 // retain multiline comment with @license
 uglifyOpts.output.comments = (node, comment) =>
 comment.type === 'comment2' && /@license/i.test(comment.value);
 
-var plugins = [
+const onwarn = (warning) => {
+  // Suppress this error message... https://github.com/rollup/rollup/wiki/Troubleshooting#this-is-undefined
+  const ignores = ['THIS_IS_UNDEFINED'];
+  if (!ignores.some(code => code === warning.code)) {
+    console.error(warning.message);
+  }
+};
+
+const plugins = [
   nodeResolve({jsnext: true}),
   progress({ clearLine: false }),
   sourcemaps(),
@@ -29,7 +37,7 @@ var plugins = [
 
 if (MINIFY) plugins.push(uglify(uglifyOpts));
 
-var extension = MINIFY ? ".min.js" : ".js";
+const extension = MINIFY ? ".min.js" : ".js";
 
 const CONFIG = {
   moduleName: '@uirouter/core',
@@ -41,6 +49,7 @@ const CONFIG = {
   exports: 'named',
   plugins: plugins,
   banner: banner,
+  onwarn: onwarn,
 };
 
 export default CONFIG;