NixOS/nix

Add builtins.canonicalPath

Open

#13,111 opened on Apr 29, 2025

View on GitHub
 (5 comments) (1 reaction) (0 assignees)C++ (1,293 forks)batch import
featuregood first issueidea approved

Repository metrics

Stars
 (9,803 stars)
PR merge metrics
 (Avg merge 7d 11h) (83 merged PRs in 30d)

Description

Is your feature request related to a problem?

Symlinks in nixpkgs lib.fileset are causing issues: https://github.com/NixOS/nixpkgs/issues/393845 and this function would help resolve it.

Proposed solution

Add a a builtins.canonicalPath with the same behavior as the realpath command, as suggested by @infinisil .

Alternative solutions

Additional context

Possibly somewhat related: https://github.com/NixOS/nix/issues/2109 (but this feature request would only expose a new nix function, not change anything else inside the nixcpp code itself.

Checklist

Add :+1: to issues you find important.

Contributor guide

Research direction
Examine existing builtins in Nix source code (e.g., builtins.fetchurl) and implement builtins.canonicalPath using similar patterns, likely by resolving symlinks via standard C++ filesystem operations.
Tech stack
None
Domain
clibackend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Nix internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30