rustPlatform.buildRustPackage: miscelaneous modernization to unify unpackPhase and cargoDeps.unpackPhase

[ShamrockLee]

1. Pass all environment variables (including RUST_LOG) via env
2. Run cargoDepsHook (a hook for tweaks before Rust vendor from cargoDeps or cargoVendorDir gets unpacked) inside cargoSetupPostUnpackHook instead of prepending to postUnpack.
3. Make it feasible to unify the postUnpack of the main derivation and cargoDeps in PR rustPlatform.buildRustPackage: fix cargoDeps inherited attribute overriding #435239

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[ShamrockLee]

@ofborg build nnd
@ofborg build scuba
@ofborg build tests.fetchtorrent.http-link-rqbit tests.fetchtorrent.http-link-rqbit-flattened
tests.fetchtorrent.http-link-rqbit-unflattened tests.fetchtorrent.magnet-link-rqbit tests.fetchtorrent.magnet-link-rqbit-flattened tests.fetchtorrent.magnet-link-rqbit-unflattened

[ShamrockLee]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review --package nnd --package scuba --package libchewing --package uwc
Commit: 8613150cc4e1987e70fae2c04efa922edb1df2c8

---

x86_64-linux

✅ 5 packages built:

• libchewing
• nnd
• scuba
• scuba.dist (scuba.dist.dist)
• uwc

Note

The above nixpkgs-review --branch is set to nixos-unstable (which is the before the merge base of master and staging) to reduce rebuilds.

[ShamrockLee]

@ofborg build cargo

rustPlatform.buildRustPackage + cargoHash
@ofborg build uwc

rustPlatform.buildRustPackage + cargoHash + postPatch
@ofborg build rqbit

stdenv.mkDerivation + rustPlatform.cargoSetupHook
@ofborg build libchewing

pkgsCross.musl64.rustPlatform.buildRustPackage + cargoHash
@ofborg build nnd

pkgsStatic.rustPlatform.buildRustPackage + cargoHash + sourceRoot used inside a Python application
@ofborg build scuba

RUSTFLAGS specified as a list; additional env specified
@ofborg build cosmic-edit

[ShamrockLee]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review --package cosmic-edit --package rqbit --package cargo
Commit: 8613150cc4e1987e70fae2c04efa922edb1df2c8

---

x86_64-linux

✅ 3 packages built:

• cargo
• cosmic-edit
• rqbit

Note

The above nixpkgs-review --branch is set to nixos-unstable (which is the before the merge base of master and staging) to reduce rebuilds.

[wolfgangwalther]

Is this specification as a list already happening or an extension? The previous code didn't do that, so I suspect that this would be a bug fix, if there were already cases for it?

With this upper-case spelling, I'd argue that this should be treated as an environment variable and thus lists should not be supported anywhere.

If we want a structured way to specify them, this should be come rustFlags?

[ShamrockLee]

Is this specification as a list already happening or an extension?

It is already happening.
Violated packages (via tree-wide evaluation):

• alvr
• asusctl
• cosmic-edit
• mitra
• proxmox-backup-client

The previous code didn't do that

The previous code expect it to be string-concatable via the + operator, which indicates that it should be a string. However, it is only string-concatenated in the lib.optionalAttrs block requiring buildType == debug, which is seldom triggered.

If we want a structured way to specify them, this should be come rustFlags?

I think so. While implementing #359744, I gradually think that we should prepend goFlags/rustFlags explicitly to the compiler flags instead of relying on the GOFLAGS/RUSTFLAGS environment variables. Let's implement such interface change in a separate PR.

[wolfgangwalther]

Diff LGTM, didn't test. I don't know enough about the Rust / Cargo ecosystem in Nixpkgs to say too much beyond simply reading the code.

[ShamrockLee]

We no longer have to consider backporting to Nixpkgs 25.05.

I'll drop some overly conservative backport compatibility code.

[wolfgangwalther]

Fails eval in the queue!

[ShamrockLee]

Let's rebase and try again.

[ShamrockLee]

I see. I forgot to handle the null values.

[gepbird]

I got a new failing build and bisected to this PR, more specifically to this diff:

diff --git a/pkgs/build-support/rust/build-rust-package/default.nix b/pkgs/build-support/rust/build-rust-package/default.nix
index 577463a0f689..bc2372278283 100644
--- a/pkgs/build-support/rust/build-rust-package/default.nix
+++ b/pkgs/build-support/rust/build-rust-package/default.nix
@@ -33,6 +33,7 @@ lib.extendMkDerivation {
     "cargoUpdateHook"
     "cargoLock"
     "useFetchCargoVendor"
+    "RUSTFLAGS"
   ];
 
   extendDrvArgs =
@@ -89,6 +90,10 @@ lib.extendMkDerivation {
       true;
 
     {
+      env = {
+        RUSTFLAGS = interpolateString (args.RUSTFLAGS or "");
+      };
+
       cargoDeps =
         if cargoVendorDir != null then
           null

The package sets CARGO_TARGET_X86_64_PC_WINDOWS_GNU_RUSTFLAGS variable. Before this change env | grep RUSTFLAGS results in:

CARGO_TARGET_X86_64_PC_WINDOWS_GNU_RUSTFLAGS=-L /nix/store/kchvqpqwlnh0442x75bj4y7hrghv9sh9-mingw_w64-pthreads-x86_64-w64-mingw32-13.0.0/lib                                                    

And after the change it results in:

CARGO_TARGET_X86_64_PC_WINDOWS_GNU_RUSTFLAGS=-L /nix/store/kchvqpqwlnh0442x75bj4y7hrghv9sh9-mingw_w64-pthreads-x86_64-w64-mingw32-13.0.0/lib                                                    
RUSTFLAGS=                                                                                                                                                                                      

This causes the first variable to be ignored and generates this error: /nix/store/7via7kz8xlfwimvmpncf8ldda8chjpsc-x86_64-w64-mingw32-binutils-2.44/bin/x86_64-w64-mingw32-ld: cannot find -l:libpthread.a: No such file or directory