missing field unused for key patch

[jmgilman]

 > error: failed to parse lock file at: /build/dummy-src/Cargo.lock
 >
 > Caused by:
 >   missing field `unused` for key `patch`
 > [naersk] cargo returned with exit code 101, exiting

I am getting the above error when building a lockfile with entries like:

[[patch.unused]]
name = "package"
version = "0.1.0"
source = "git+https://github.com/org/repo.git?branch=mybranch#efe089af522e424d1099407b6585efe042ad085f"

I can run this same lockfile with cargo outside of Nix and it compiles fine. I'm having trouble understanding what specifically is making it break when trying to build it with naersk.

[Patryk27]

Curiously, there's one-and-a-half worth of bugs here!

tl;dr I've just prepared a fix - after it's merged, you'll have to update your Nixpkgs to a newer version (at least 23, i.e. current master or nixpkgs-unstable), and then bump Naersk.

---

First, when Naersk builds a derivation, it converts Cargo.lock into a Nix attrset and then reserializes that attrset back into a TOML document later - this serialization-code has had a bug that caused the eventual Cargo.lock to look like:

[patch]
[[unused]]
name = "package"
version = "0.1.0"
source = "..."

... which Cargo (rightfully) doesn't understand anymore.

This bug has been fixed recently, but the fix only works when Naersk is launched on Nixpkgs 23+ (because older versions of Nixpkgs had a buggy serializer as well) - so, in principle, if you switched to a newer Nixpkgs (e.g. nix flake lock --update-input naersk --update-input nixpkgs), it should work.

But, as it turns out, there's second thing at play here - because Naersk doesn't provide sources for ignored dependencies, trying to actually compile such project will fail, saying:

failed to resolve address for github.com: nodename nor servname provided, or not known; class=Net (12)

... as Cargo will try to download the "missing" dependency on its own, while being locked in Nix sandbox, which fails.

This is a bug on Naersk's side, for which I've just prepared a fix.