by Joakim

JavaScript file missing from resource bundle (ASP.NET Web Optimization Framework)

I came across some odd behavior related to the Microsoft ASP.NET Web optimization Framework the other day, when I was creating a JavaScript resource bundle in an application I was working on. When I ran the website with optimizations enabled, the script file showed up as part of the bundle, but if I turned optimizations off the script include for the file in question was nowhere to be found.

For the application I was working on, which was only a proof of concept, I had simply copied the minified version of the JavaScript libraries I needed into the Script manually. I then included my libraries in a script bundle like so;

If you have used this bundling functionality before, you probably know that if you include a JavaScript file in a bundle and you enable optimizations, the file will be minified and added to a single resource together with any other JavaScript files in the bundle. During the minification process the system will look for other files in the directory called exactly the same filename as the file in question only with .min.js at the end instead of only .js. If it finds a file like this, it assumes that this it is a pre-minified version of the file in question and uses it instead of minifying the original file.

However, if you add a file to your bundle that has a name that ends in .min.js (like I did) and optimizations aren’t enabled (e.g. debug is set to true in web.config and BundleTable.EnableOptimizations has not been set to true), this file will be ignored (i.e no script include will be generated for it in your html).