---

name: update-rust-derivation description: Update a Rust derivation to a new version with correct hashes. Use when the user wants to update a Rust package in their nix derivations.

Update Rust Derivation

Update the Rust derivation: $ARGUMENTS

Steps

1. Read the derivation: Read the derivation file to understand its current structure, version, and hash fields.

2. Update the version: Change the version attribute to the new version.

3. Get the source hash:

   Copynix-prefetch-url --unpack "https://github.com/<owner>/<repo>/archive/refs/tags/v<version>.tar.gz"
   

   Then convert to SRI format:

   Copynix hash to-sri --type sha256 <hash>
   

4. Update the source hash: Replace the hash attribute in fetchFromGitHub with the new SRI hash.

5. Set cargoHash to placeholder: Temporarily set cargoHash = lib.fakeHash; to trigger nix to compute the correct hash.

6. Build to get cargoHash:

   Copynix build --impure --expr 'let pkgs = import <nixpkgs> {}; in pkgs.callPackage ./<path-to-derivation> {}' 2>&1 | grep -A2 "got:"
   

   Extract the correct cargoHash from the error output.

7. Update cargoHash: Replace lib.fakeHash with the actual cargoHash from the build output.

8. Verify the build:

   Copynix build --impure --expr 'let pkgs = import <nixpkgs> {}; in pkgs.callPackage ./<path-to-derivation> {}'
   

   Ensure the build completes successfully.

9. Summary: Report the version update (old -> new) and remind to run darwin-rebuild switch --flake . to apply changes.

Notes

• The derivation must use rustPlatform.buildRustPackage with cargoHash
• If using cargoLock instead of cargoHash, the process differs (fetch Cargo.lock from repo)
• Some packages may have additional attributes that need updating (e.g., patches, buildInputs)