nix-debugging

What problem does it solve?

This Skill helps developers rapidly diagnose and resolve Nix evaluation and build failures by consolidating common error patterns and targeted debugging techniques. It reduces time spent chasing obscure evaluation errors, infinite recursion, hash mismatches, import-from-derivation issues, collision errors, and unexpected closure size or store path problems.

Core Features & Use Cases

• Evaluation and Recursion Diagnosis: Techniques to locate sources of infinite recursion and attribute-missing errors using tracing and careful overlay usage.
• Build and Hash Recovery: Guidance on resolving fixed-output derivation hash mismatches, handling unfree packages, and avoiding IFD by prefetching or adjusting fetchers.
• Closure, Logs, and Dependency Analysis: Use cases for nix log, nix why-depends, nix path-info, and store inspection to find unexpected dependencies, large closures, and to interpret build logs for fixes.
• Real-world Example: When an overlay causes infinite recursion or a package fails with a hash mismatch, the Skill walks through using builtins.trace, nix eval, and build debugging steps to isolate and fix the root cause.

Quick Start

Ask the skill to analyze a Nix evaluation or build error and produce targeted debugging steps.