Mix Tasks & Generators

RULES — Follow these with no exceptions

1. Always call Mix.Task.run("app.start") first — tasks that access the database or Repo need the app started
2. Create custom tasks for project-specific workflows — don't override standard Mix tasks
3. Use OptionParser.parse/2 for argument parsing — never use raw System.argv() for complex arguments
4. Add @shortdoc to every task — tasks appear in mix help using this attribute
5. Register preferred_cli_env in mix.exs — set environment for custom tasks (dev/test/prod)
6. Use transactions for data modifications — wrap Repo.insert_all, Repo.delete_all in Repo.transaction()
7. Test custom tasks with Mix.Project.in_project/4 — ensure tasks work correctly in isolation
8. Follow Mix.Tasks.Namespace.TaskName naming — file path must match: lib/mix/tasks/namespace.task_name.ex

End-to-End Workflow

Follow this sequence when creating a custom Mix task: