Thats the point. Who says it has to be a config file? Think outside the box.

Here is how Flask can do configuration (a Python micro framework):

<code>

class Config(object):

    DEBUG = False

    TESTING = False

    DATABASE_URI = 'sqlite://:memory:'

class ProductionConfig(Config):

    DATABASE_URI = 'mysql://user@localhost/foo'

class DevelopmentConfig(Config):

    DEBUG = True

class TestinConfig(Config):

    TESTING = True

</code>

Zend Framework also handles configs with inheritance. It's an elegant way to handle overrides, no doubt. They do one better by allowing the definition to be in ini files, which would have circumvented the Tumblr bug.

Still, I think config files are often best when they're verbose and as straightforward as possible. There are fewer surprises this way. If I'm working on a project by myself or with a very small team of people I trust, I'd go the inheritance route. If the team is larger, I'd go the verbose route.

I pretty much agree with jjm comment. I never have ONE config file but a directory of config files, everything is separated : database, memcache, heywatch, s3, routes, ... It's way easier for the developer, the sysadmin, the deployment, ... Of course it would multiply the risk of this happening by n files.