rustPackages.clippy fails to compile: can't find crate fmt_macros

[curiousleo]

Describe the bug

nix-build . -A rustPackages.clippy fails on master since e82fae1 with this error:

   Compiling clippy_lints v0.0.212 (/build/rustc-1.40.0-src/src/tools/clippy/clippy_lints)
error[E0463]: can't find crate for `fmt_macros`
  --> src/tools/clippy/clippy_lints/src/lib.rs:20:1
   |
20 | extern crate fmt_macros;
   | ^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

To Reproduce
Steps to reproduce the behavior:

1. Check out any commit between e82fae1 and master
2. nix-build . -A rustPackages.clippy
3. Observe the compilation failure pasted above.

Expected behavior
nix-build . -A rustPackages.clippy should succeed.

Additional context
I discovered this build failure in the context of #77327.

Metadata

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 4.19.93, NixOS, 19.09.1778.db3e8325a9b (Loris)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.1`
 - channels(root): `"nixos-19.09.1778.db3e8325a9b"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:

[curiousleo]

rust-lang/rust-clippy#4651 points to rust-lang/rust#64823 being the root cause of this type of error - it looks like we'll need to pull in the rustc-dev component somehow and build clippy against that.

[curiousleo]

rust-lang/rust#64823 was reverted in rust-lang/rust#65342 due to rust-lang/rust#65335 ...

[curiousleo]

... and then re-applied with some changes: rust-lang/rust#65474.

[curiousleo]

... and then in rust-lang/rust#67469, rustc-dev (on which clippy_lints depends) was removed from the default set of components shipped with Rust nightly.

[curiousleo]

On the clippy side, this PR (re-)introduced the extern crate declarations that lead to the compilation error (though this is probably just a symptom, not the cause): rust-lang/rust-clippy#3189

[curiousleo]

(Very tangentially related: https://guix.gnu.org/blog/2018/bootstrapping-rust/, https://github.com/thepowersgang/mrustc)

[curiousleo]

There may be an alternative way of building clippy: together with rustc, via --tools=clippy in https://github.com/rust-lang/rust/blob/1.40.0/src/bootstrap/configure.py#L157, which is forwarded to the install script here: https://github.com/rust-lang/rust/blob/1.40.0/src/bootstrap/install.rs#L160

[Mic92]

How does upstream build clippy?

[mati865]

How does upstream build clippy?

By enabling this option.

[curiousleo]

How does upstream build clippy?

Good question :) Looking into this, I filed rust-lang/rust-clippy#5037.

clippy is referenced from the rust repository as a submodule.

• https://github.com/rust-lang/rust/blob/1.40.0/.gitmodules#L19-L21
• https://github.com/rust-lang/rust/tree/1.40.0/src/tools

The commit at which clippy is pinned in rust 1.40 is rust-lang/rust-clippy@c8e3cfb. Interestingly, that commit actually failed CI, though I can't tell why.

[curiousleo]

How does upstream build clippy?

By enabling this option.

Alternatively, as per my suggestion above: setting the tools option.

[curiousleo]

@mati865, do you happen to know the entry point (a script or CI configuration) that is used to release clippy (as opposed to the CI in the clippy repo used for testing purposes)?

[mati865]

@curiousleo tools option is the list of the tools that will be built if extended option (which I linked above) is enabled.

Clippy is using unstable compiler API and thus is not meant to be built separately (stable and beta compilers will throw an error about unstable features unless unsupported hack is applied). AFAIK Clippy releases are done manually.

[curiousleo]

@curiousleo tools option is the list of the tools that will be built if extended option (which I linked above) is enabled.

Awesome, I missed that! I don't think the way the comments are phrased make this unambiguous. Okay, I'll see if I can get this to work using --extended.

Clippy is using unstable compiler API and thus is not meant to be built separately (stable and beta compilers will throw an error about unstable features unless unsupported hack is applied). AFAIK Clippy releases are done manually.

Good to know. Thanks!

[curiousleo]

I've managed to build clippy by adding --enable-extended and --tools=clippy to the rustc build arguments. That could be one way of getting clippy built.

Currently testing whether #77529 simply fixes this issue.

[curiousleo]

I can confirm that #77529 allows nix-build . -A clippy to go through without an error.

I'll leave this issue open until #77529 is in master.

[curiousleo]

#77529 will land in master as part of #77739: https://github.com/NixOS/nixpkgs/pull/77739/files#diff-fb2bc02945c6ee61a9ea9fd6aeddd789.

[curiousleo]

#77739 has been merged, and nix-build . -A clippy now succeeds on master. Closing.