Modifying contributed Drupal modules

It surprised me that some people think it's not ok to alter contributed modules. Well, its not. It's a bad thing to adjust CORE modules! But that's another discussion. The idea is that before programming your own module you try to find one that already does most of what you want, but misses some features. you will code those features. Sometimes this involves only adding a few lines or adding only one function. Sometimes it involves a lot of programming.

The big problem with altering contributed modules is that you loose the ability to upgrade when a new version of the module is released. In an article about upgrading Drupal, Wim Mostrey proposes a simple solution to keep track of what you are changing.

I started of by dividing the non-core modules between those still in their original state to a "contrib" directory and those that were either completely custom or altered in a "custom" directory, to get the following tree structure:
/sites/all/modules/contrib
/sites/all/modules/custom

This helps you identify what needs to happen and will also save a lot of work for future upgrades. I then started from a clean Drupal 5.3 installation, download the newest version of the modules in /contrib and then started a process of 1) moving the core changes to non-core modules and themes and 2) updating the /custom modules.

But this way, you're only keeping track of what modules have changed. My addition to this tip is that you make a copy of the files you alter and name it .contributed or .original or .backup or .whatever-you-get-my-point (example: tinymce.module.contributed). Now you are keeping track of what files are modified too! And as soon as you need to upgrade, make a quick diff and you know what has changed.

BTW. If you find yourself tweaking a contributed module, why not contribute your new features, improvements? Maybe someone else is looking for it too.