🐥 Detecting compile-time cycles in Elixir with mix xref

When working on large Elixir projects, keeping module dependencies clean and acyclic is essential to maintain compile performance and avoid circular references. Elixir provides a helpful tool for this: mix xref.

Here’s a quick command to detect compile-time dependency cycles:

mix xref graph --format cycles --label compile-connected --fail-above 0

What it does:

• --format cycles: Shows only cyclic dependencies in the module graph.
• --label compile-connected: Focuses on compile-time references (e.g., module definitions, struct usage, macros).
• --fail-above 0: Fails the command if any cycle is found (great for CI).

Example output:

== Compilation graph cycle ==
Foo -> Bar -> Baz -> Foo

Compile-time cycles can:

• Force modules to be recompiled unnecessarily.
• Introduce brittle dependencies that are hard to test and maintain.
• Break upgrades in hot code reload scenarios.

Integrate this command in your CI pipeline to prevent new cycles from creeping in:

mix xref graph --format cycles --label compile-connected --fail-above 0

A failing build is a small price to pay for a healthier codebase.