Why did Heroku stop precompiling my assets?

I come into work today to this error:

ActionView::Template::Error ('twitter/bootstrap/bootstrap.less' wasn't found.

Odd...It works in development. What could have happened?

The search

I ran the application locally with the development environment and got the same error. Great, at least it's reproducible. Let's hit the Googles...

Hmm, some mentions in twitter-bootstrap-rails and some scattered StackOverflow questions, but nothing that works. Then I noticed Heroku was no longer precompiling the assets on deploy.

The discovery

The Heroku docs have this glorious quote:

The most common cause of failures in assets:precompile is an app that relies on having its environment present to boot. Your app's config vars are not present in the environment during slug compilation, so you should take steps to handle the nil case for config vars (and add-on resources) in your initializers.

A recent change added some configuration variables in application.rb that referenced some environment variables.

The fix

Based on some more documentation and community help, I moved the configuration into an initializer that is loaded after the slug compilation when it can access the environment variables.

Deploy. Working. #winning.

MySQL installation woes on Mountain Lion

After doing a fresh installation with Mountain Lion, I've had a hell of a time properly install MySQL. I've had to use a few sources to figure this one out, and here are the steps I needed to take.

I'm not 100% sure that these steps are needed, but they couldn't hurt

1. sudo chown -R `whoami` /usr/local
2. brew update

Some background.

1. brew install mysql
2. sudo mysql_install_db --user=mysql --tmpdir=/tmp --basedir=/usr/local
3. mysql.server start

Now test with

mysql -uroot

Squashing bugs with Git

We found a bug at work where a css style changed, but it wasn't immediately obvious where it had been introduced. To fix this bug, I went back through the git history and checked out one in the recent past to see if the bug had been introduced there. This only took a few tries, and then I worked back toward the present to find when the styling had been modified.

I found the offending commit by checking out the sass file of that particular commit:

git checkout {commit_number} path/to/stylesheet.sass

Now I've got the most recent code plus the file that fixes the problem. To see what had been changed, I did a diff on the two files: the older one without the bug and the next one with the bug:

git diff {older_commit} {newer_commit} path/to/stylesheet.sass

There are a lot of changes, so I looked for anything that would be obvious (margins in this case). After that, it was modifying the styling to fix the bug and done.

Git plays nice.