The External Links module for Drupal is a nice, unobtrusive addition that adds an arrow icon next to off-site links to let users know the link will take them to a new site and open a new browser window. There is also a cool feature to include or exclude links based on regular expressions. Wheeeee!!!!!

Be warned, however, that you may enter a valid regular expression that could cause the javascript on your site to take a header. You will immediately know this is the case when you save your changes and the fieldset for the pattern matching is no longer collapsible. What happens is that the regular expression you entered is not validated against potential conflicts in the javascript that parses it on rendering. We had this issue when we tried to add an inclusion rule for PDF's. We wanted all PDF's hosted on the site to open a new window, despite the fact that they were 'internal'. Seems easy, add a wildcard and the extension and call it a day....

*.pdf

That didn't work. This isn't command line DOS, or *nix- add an escape to look for the period. It also broke Javascript on the site!

Drush to the rescue.

This went from a quick module addition to a murder mystery, minus the murder. Well, when clients aren't happy it might. Here's how we diagnosed the issue, which turned out to be fairly simple, but the troubleshooting process is important.
First off, since we work in a development site no one was going to be adversely affected. Next we know what was going on at the time things broke. I was the only one working on the site at the time so that narrowed it down to me and the changes I was making. If you have multiple developers working on a site concurrently, then version control, and backups are paramount.

So, we know I broke the site, and it was something to do with the External Links and specifically the regular expression I had just tried to save. This most likely means that the module saves data to the database in a custom table, or as a site variable. Drush can help inspect the second route very quickly-

% drush vget extlink
extlink_alert: 0
extlink_alert_text: "This link will take you to an external web site. We are not responsible for their content."
extlink_class: "ext"
extlink_exclude: ""
extlink_include: "*.pdf"
extlink_mailto_class: "mailto"
extlink_subdomains: 1
extlink_target: "_blank"

There it is! If no variables were found, then the next step is to check out the .install file for the offending module and look for a schema hook. But, we lucked out and can move along to spewing poorly formed regular expressions.

% drush vdel extlink_include and refresh, and we're back in business.
*.pdf


That didn't work, duh. This must be a 'javascript supported' pattern as the documentation says.

.*.pdf.


And now PDF's will open in a new window.

Links:

External Links