GAE App.yaml - separate directories for src and build static files

Question

Is it possible to optionally override a static files directory in the Google App Engine app.yaml file if another directory exists? I have a source directory (unminified) and a build directory (minified and concatenated). I want Google App Engine to automatically use the build directory instead of the src directory, if it exists. That way I can dev using the src directory, then create a build and deploy it. Then, if I delete the build directory, GAE goes back to serving my static files from the src directory.

The reason I need to do this is because I am building an application with Backbone.js & Require.js as modules. I need to be able to optimize my code and deploy without changing my app.yaml file every time.

Answer 1

I'm pretty happy with my current system where my framework uses different paths in the templates to the source javascript files. Then at startup, through a combination of checking os.environ and get_application_id() I automatically detect whether I'm running locally on dev_appserver, or under my test appid or production appid on GAE.

And on to the next step, you most likely want to cache your minified JS aggressively, in which case you'd be unable to force clients to update a new version. The typical workaround is to append a hash or date string to the minified js filename whenever it's updated. This is something you'll also need to do in your framework/templating layer instead of app.yaml.

Answer 2

I would do this at the template layer - when you go to render the template that includes links to your assets, check to see if the minified version exists. If it does, link to that - otherwise, link to the unminified version.

This also helps if you accidentally deploy without creating a build - you'll just be serving unoptimized assets.