URL-rewriting in CherryPy 2.1 and TurboGears
Robert “FuManChu” Brewer goes in-depth on URL-rewriting in CherryPy 2.1. This is some documentation I wish I had a couple weeks ago. Robert sums up which aspects of mounting apps at arbitrary points are broken:
1. Generating URL’s to spit back out in HTML. Broken. I now have to manually provide prefix to my HTML templates, or take on the nightmare of making every generated URL into a URL which is relative (e.g. “../../otherpage”) to the current one.
2. HTTP Redirects and their targets. Broken. I now have to manually provide prefix to each instance (or use relative URL’s). But I can’t control CherryPy’s redirect instances! For example, when CherryPy tries to redirect index methods by adding a trailing slash to the requested URI, it uses the value of path, which I’ve rewritten.
3. Handler dispatch: not broken.
4. Arbitrary mount points: not broken.
5. Config lookups. Broken? Some other filter which does a config lookup could run their onStartResource method before mine. Since my filter is user-defined, it is forced to run after all of the builtin ones; none of those currently perform config lookups, however. If any of the server.* config entries are specified somewhere other than “global”, then we have the same issue. Finally, what’s to stop a future CP developer from adding more such problems (as they fix other bugs)?
6. Logging: the error.log and access.log will both use the original URI (from requestLine). Broken? or not? One? Both?
I should note that TurboGears has a fix for #1 and #2 on the list, in the form of an included URL generation function that takes the application root into account. #2 is actually only partly fixed by the URL function. CherryPy’s built in trailing slash redirect knows nothing about my little URL function. There’s a ticket open in the TurboGears Trac about static resources in mounted apps that is basically consideration #5 on Robert’s list. I hadn’t looked at the logging aspect of the problem, so I’ll definitely take Robert’s word on the state of it.
Will this be fixed by .9?
Not unless someone submits a patch for it. There are some tricky issues, and we’ll likely have to come up with some workarounds that get us most of the way there before CherryPy has it fully fixed.