Last Updated: 2024-04-19

I had a deploy script for Heroku:

set -e

heroku run rake db:migrate
... # other commands that must ONLY run if the migration was successful

My migrations on Heroku failed, yet the subsequent commands ran. This is because heroku run rake db:migrate always returns exit code 0 even on error conditions (annoyingly...)

The fix was to scan the output

if heroku run rake db:migrate | grep "rake aborted!"; then
  exit 1
fi

Lessons

• If I am depending on set -e to halt, ensure that the component commands actually exit non-zero on failure. Refer to docs (and test if non-available).
• When designing my own software tools, always exit code non-zero on failure.