haskellPackages.opencv: Fails to evaluate in nixpkgs-review with local evaluation

[OPNA2608]

Nixpkgs version

• Unstable (25.11)

Describe the bug

I have aliases disabled on my system, so pkgs.opencv3 just doesn't exist anymore. When trying to evaluate haskellPackages.opencv.buildInputs, the evaluation fails:

nix-repl> haskellPackages.opencv.buildInputs
error:
       … while evaluating the attribute 'opencv.buildInputs'
         at /home/puna/Development/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:590:13:
          589|             depsHostHost = elemAt (elemAt dependencies 1) 0;
          590|             buildInputs = elemAt (elemAt dependencies 1) 1;
             |             ^
          591|             depsTargetTarget = elemAt (elemAt dependencies 2) 0;

       … while calling the 'elemAt' builtin
         at /home/puna/Development/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:590:27:
          589|             depsHostHost = elemAt (elemAt dependencies 1) 0;
          590|             buildInputs = elemAt (elemAt dependencies 1) 1;
             |                           ^
          591|             depsTargetTarget = elemAt (elemAt dependencies 2) 0;

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: attribute 'opencv3' missing
       at /home/puna/Development/nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix:492098:22:
        492097|     }
        492098|   ) { inherit (pkgs) opencv3; };
             |                      ^
        492099|
       Did you mean one of opencv, opencv4, opencbm, opencc or opencpn?

I'm not sure why nixpkgs-review is choosing to evaluate this despite the derivation being meta.broken…

Steps to reproduce

I hit this while trying to nixpkgs-review #438979 with local evaluation. Evaluating haskellPackages.opencv.buildInputs with aliases disabled achieves the same error.

Expected behaviour

We don't like to rely on aliases in Nixpkgs. It would be nice if this still evaluated, even if it's long-term broken & waiting for a bump from upstream.

Screenshots

No response

Relevant log output

Local evaluation for computing rebuilds
$ nix-env --extra-experimental-features no-url-literals --option system x86_64-linux -f <nixpkgs> --nix-path nixpkgs=/home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs nixpkgs-overlays=/tmp/tmp_onhbbeq -qaP --xml --out-path --show-trace --no-allow-import-from-derivation
error:
       … while querying the derivation named 'opencv-0.0.2.1'

       … while calling the 'getAttr' builtin
         at <nix/derivation-internal.nix>:50:17:
           49|     value = commonAttrs // {
           50|       outPath = builtins.getAttr outputName strict;
             |                 ^
           51|       drvPath = strict.drvPath;

       … while calling the 'derivationStrict' builtin
         at <nix/derivation-internal.nix>:37:12:
           36|
           37|   strict = derivationStrict drvAttrs;
             |            ^
           38|

       … while evaluating derivation 'opencv-0.0.2.1'
         whose name attribute is located at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:538:13

       … while evaluating attribute 'buildInputs' of derivation 'opencv-0.0.2.1'
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:590:13:
          589|             depsHostHost = elemAt (elemAt dependencies 1) 0;
          590|             buildInputs = elemAt (elemAt dependencies 1) 1;
             |             ^
          591|             depsTargetTarget = elemAt (elemAt dependencies 2) 0;

       … while calling the 'elemAt' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:590:27:
          589|             depsHostHost = elemAt (elemAt dependencies 1) 0;
          590|             buildInputs = elemAt (elemAt dependencies 1) 1;
             |                           ^
          591|             depsTargetTarget = elemAt (elemAt dependencies 2) 0;

       … while calling the 'map' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:500:14:
          499|             (map (drv: getDev drv.__spliced.hostHost or drv) (checkDependencyList "depsHostHost" depsHostHost))
          500|             (map (drv: getDev drv.__spliced.hostTarget or drv) (checkDependencyList "buildInputs" buildInputs'))
             |              ^
          501|           ]

       … from call site
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:500:65:
          499|             (map (drv: getDev drv.__spliced.hostHost or drv) (checkDependencyList "depsHostHost" depsHostHost))
          500|             (map (drv: getDev drv.__spliced.hostTarget or drv) (checkDependencyList "buildInputs" buildInputs'))
             |                                                                 ^
          501|           ]

       … while calling 'checkDependencyList''
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:446:26:
          445|       checkDependencyList' =
          446|         positions: name: deps:
             |                          ^
          447|         imap1 (

       … from call site
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:447:9:
          446|         positions: name: deps:
          447|         imap1 (
             |         ^
          448|           index: dep:

       … while calling 'imap1'
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/lib/lists.nix:345:14:
          344|   */
          345|   imap1 = f: list: genList (n: f (n + 1) (elemAt list n)) (length list);
             |              ^
          346|

       … while calling the 'genList' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/lib/lists.nix:345:20:
          344|   */
          345|   imap1 = f: list: genList (n: f (n + 1) (elemAt list n)) (length list);
             |                    ^
          346|

       … while evaluating the second argument passed to builtins.genList

       … while calling the 'length' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/lib/lists.nix:345:60:
          344|   */
          345|   imap1 = f: list: genList (n: f (n + 1) (elemAt list n)) (length list);
             |                                                            ^
          346|

       … from call site
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:431:7:
          430|     if __propagatePkgConfigDepends then
          431|       propagatePlainBuildInputs allPkgconfigDepends'
             |       ^
          432|     else

       … while calling 'propagatePlainBuildInputs'
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:405:9:
          404|       propagatePlainBuildInputs =
          405|         drvs:
             |         ^
          406|         builtins.map (i: i.val) (

       … while calling the 'map' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:406:9:
          405|         drvs:
          406|         builtins.map (i: i.val) (
             |         ^
          407|           builtins.genericClosure {

       … while calling the 'genericClosure' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:407:11:
          406|         builtins.map (i: i.val) (
          407|           builtins.genericClosure {
             |           ^
          408|             startSet = builtins.map (drv: {

       … while calling the 'map' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:408:24:
          407|           builtins.genericClosure {
          408|             startSet = builtins.map (drv: {
             |                        ^
          409|               key = drv.outPath;

       … while calling the 'filter' builtin
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:411:17:
          410|               val = drv;
          411|             }) (builtins.filter propagateValue drvs);
             |                 ^
          412|             operator =

       … while calling 'propagateValue'
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:399:9:
          398|       propagateValue =
          399|         drv: lib.isDerivation drv && (__onlyPropagateKnownPkgConfigModules -> drv ? meta.pkgConfigModules);
             |         ^
          400|

       … in the left operand of the AND (&&) operator
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:399:35:
          398|       propagateValue =
          399|         drv: lib.isDerivation drv && (__onlyPropagateKnownPkgConfigModules -> drv ? meta.pkgConfigModules);
             |                                   ^
          400|

       … from call site
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/generic-builder.nix:399:14:
          398|       propagateValue =
          399|         drv: lib.isDerivation drv && (__onlyPropagateKnownPkgConfigModules -> drv ? meta.pkgConfigModules);
             |              ^
          400|

       … while calling 'isDerivation'
         at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/lib/attrsets.nix:1298:18:
         1297|   */
         1298|   isDerivation = value: value.type or null == "derivation";
             |                  ^
         1299|

       error: attribute 'opencv3' missing
       at /home/puna/.cache/nixpkgs-review/pr-438979/nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix:492098:22:
        492097|     }
        492098|   ) { inherit (pkgs) opencv3; };
             |                      ^
        492099|
       Did you mean one of opencv, opencv4, opencbm, opencc or opencpn?
https://github.com/NixOS/nixpkgs/pull/438979 failed to build: Failed to list packages: nix-env failed with exit code 1

Additional context

No response

System metadata

• system: "x86_64-linux"
• host os: Linux 6.16.0, NixOS, 25.11 (Xantusia), 25.11pre837094.94def634a204
• multi-user?: yes
• sandbox: yes
• version: nix-env (Lix, like Nix) 2.91.3 System type: x86_64-linux Additional system types: i686-linux, powerpc64-linux Features: gc, signed-caches System configuration file: /etc/nix/nix.conf User configuration files: /home/puna/.config/nix/nix.conf:/etc/xdg/nix/nix.conf:/home/puna/.nix-profile/etc/xdg/nix/nix.conf:/nix/profile/etc/xdg/nix/nix.conf:/home/puna/.local/state/nix/profile/etc/xdg/nix/nix.conf:/etc/profiles/per-user/puna/etc/xdg/nix/nix.conf:/nix/var/nix/profiles/default/etc/xdg/nix/nix.conf:/run/current-system/sw/etc/xdg/nix/nix.conf:/nix/store/wzvcw93ncl4cnw7062mn77q4ym2hmxb1-gnome-settings-daemon-48.1/etc/xdg/nix/nix.conf Store directory: /nix/store State directory: /nix/var/nix Data directory: /nix/store/77m0y0vy6hmvp7vndljl9005ynxhkvf9-lix-2.91.3/share
• channels(bt1cn): "unstable"
• channels(root): "nixos, nixos-25.05-25.05, unstable"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

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[OPNA2608]

Even with aliases enabled, I still can't get nixpkgs-review to not get stuck on this… And evaluating the buildInputs still fails, because now opencv3 is a throw:

       error: opencv3 has been removed as it is obsolete and was not used by any other package; please migrate to OpenCV 4

Guess I'll just not nixpkgs-review that PR then…

[wolfgangwalther]

Seems like we need to adjust:

https://github.com/NixOS/cabal2nix/blob/a63697c4f887c32251ab466ee2b45cbdb057059f/cabal2nix/src/Distribution/Nixpkgs/Haskell/FromCabal/PostProcess.hs#L324-L326

[sternenseemann]

We should also investigate why CI did not catch this when the alias was introduced. Maybe eval checks need to allowBroken?

[wolfgangwalther]

Unfortunately we need to ignore broken packages, because a lot of these have some other asserts or throws behind that, so we can't eval them.

NixOS/nix-eval-jobs#379 (comment) could help. Switching CI to nix-eval-jobs seams doable now, in which case we could catch each error separately - and thus also try evaluating broken packages.

[zowoq]

Seems this is the cause of ❌ nixpkgs-review failed on recent nixpkgs-update bot PRs.

[wolfgangwalther]

Fix in #439777.

[sternenseemann]

NixOS/cabal2nix#666