kafsemo.org

(Update: The current version of these notes is now in the Feed Validator docs directory, updated to include the move to Subversion and with path setup much simplified by Sam.)

With the RSS Advisory Board recommending the Feed Validator, and highlighting that it’s an open source project (Python licence), here’s a simple starter for hacking on it, either to make fixes, or simply to use it for non-public feeds.

(This is for Linux – tips for Windows or other environments are welcome!)

Get the code

The Feed Validator doesn’t make official releases, but it’s regularly updated and a current snapshot is almost always stable. Choose a local directory to store the validator in – say, ~/feedvalidator.

Download a snapshot

Nightly snapshots are available from http://feedvalidator.org/download/.

Or, use CVS

CVS is slightly more complicated to get working, but then you can keep current.

cvs -d :pserver:anonymous@cvs.sourceforge.net:/cvsroot/feedvalidator login
(No password; hit return.)
cvs -z3 -d :pserver:anonymous@cvs.sourceforge.net:/cvsroot/feedvalidator checkout feedvalidator

Later, to get the latest code, call cvs up from inside the feedvalidator directory.

Run it from the command line

There's a command-line interface:

python ./src/demo.py <feed url>

(Or, hack that script to work how you want.)

Set it up for your web server

First install a web server, Python and additional character encoding support. Under Debian:

apt-get install apache2-mpm-worker python2.3 python2.3-iconvcodec

For simplicity, it’s easiest to run the validator out of a regular user account. That means you don't need to be root.

FVDIR=<location of the feedvalidator directory>
cd ~/public_html
ln -s "$FVDIR/css" fv-css
ln -s "$FVDIR/docs" fv-docs
mkdir -p cgi-bin/fv
cp "$FVDIR/check.cgi" "$FVDIR/config.py" cgi-bin/fv/

Now, tweak config.py to point to the other directories:

WEBDIR = HOMEDIR + r'/public_html/feedvalidator'
WEBDIR = '/home/<your usercode>/feedvalidator'

DOCSURL='docs'
CSSURL='css'
DOCSURL='../../fv-docs'
CSSURL='../../fv-css'

Great!

Now open a browser to http://localhost/~<your usercode>/cgi-bin/fv/check.cgi and we’re, hopefully, done.

Running tests

I don’t think it’s any disrespect to say that that test cases are the Validator’s most valuable asset – currently over fourteen hundred separate cases of valid, and invalid, feeds, along with the precise errors. When you find a bug, or any other misfeature, a simple test case is the best way to get your point across.

To check the existing cases, run python src/validtest.py. This will check everything below the ‘testcases’ directory (you can also specify a single test by filename).

Approachable

There’s no point in having access to source code if you can’t deploy it and, even if the steps are straightforward, open source software should be as approachable as possible.