lib.addMetaAttrs: use overrideAttrs when available by winterqt · Pull Request #423615 · NixOS/nixpkgs

winterqt · 2025-07-08T21:13:38Z

Previously, any subsequent change to a derivation after an addMetaAttrs call would cause said attribute(s) to be unconditionally reset back to their previous value(s):

nix-repl> ((oldPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority
error:
    … while evaluating the attribute 'meta.priority'
        at /nix/store/nxdiklm6dnf9pma1zg7srls2nzrykrjf-nixos/nixos/pkgs/stdenv/generic/make-derivation.nix:846:17:
        845|         inherit passthru overrideAttrs;
        846|         inherit meta;
            |                 ^
        847|       }

    error: attribute 'priority' missing
    at «string»:1:67:
            1| ((oldPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority
            |                                                                   ^

This change makes it so that this does not happen (unless, of course, a subsequent override does affect those values):

nix-repl> ((newPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority
10

Fixes #323624.

Note: This work was funded by Antithesis.

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winterqt · 2025-07-08T21:14:52Z

One thing I wasn't sure about was how to cleanly get a callPackage in a test, so that this can be properly tested; though we can ofc skip testing given it's in misc.

andrewhamon

This technique is identical to that used in readTree, which has been serving me well in Discord's monorepo for over a year now. The only issue we have with readTree is the interaction with addMetaAttrs, which this PR fixes.

alyssais

Makes sense to me

eclairevoyant · 2025-07-09T12:10:39Z

Was this change tested with other meta attrs? Like position, license, etc.?

winterqt · 2025-08-27T20:33:32Z

meta.position is ✨ special ✨ in that it gets ~unconditionally overridden in check-meta:

nix-repl> ((lib.addMetaAttrs {position = "meow";} pkgs.hello).overrideAttrs {a = 1;}).meta.position
"/home/winter/src/nixpkgs/pkgs/by-name/he/hello/package.nix:47"

nix-repl> ((lib.addMetaAttrs {license = "meow";} pkgs.hello).overrideAttrs {a = 1;}).meta.license
"meow"

The way around this is to override the pos attr instead, which is used in mkDerivationSimple to set the value of meta.position:

nix-repl> ((pkgs.hello.overrideAttrs {pos = "meow";})).meta.position
error:
       … while evaluating the attribute 'meta.position'
         at /home/winter/src/nixpkgs/pkgs/stdenv/generic/check-meta.nix:616:7:
          615|     // optionalAttrs (pos != null) {
          616|       position = pos.file + ":" + toString pos.line;
             |       ^
          617|     }

       … while selecting 'file'
         at /home/winter/src/nixpkgs/pkgs/stdenv/generic/check-meta.nix:616:22:
          615|     // optionalAttrs (pos != null) {
          616|       position = pos.file + ":" + toString pos.line;
             |                      ^
          617|     }

       error: expected a set but found a string: "meow"

winterqt · 2025-08-27T20:35:00Z

Removing backport, not sure I trust this to not be a breaking change out-of-tree, even if the dependence on it is of course incorrect.

Previously, any subsequent change to a derivation after an `addMetaAttrs` call would cause said attribute(s) to be unconditionally reset back to their previous value(s): nix-repl> ((oldPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority error: … while evaluating the attribute 'meta.priority' at /nix/store/nxdiklm6dnf9pma1zg7srls2nzrykrjf-nixos/nixos/pkgs/stdenv/generic/make-derivation.nix:846:17: 845| inherit passthru overrideAttrs; 846| inherit meta; | ^ 847| } error: attribute 'priority' missing at «string»:1:67: 1| ((oldPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority | ^ This change makes it so that this does not happen (unless, of course, a subsequent override does affect those values): nix-repl> ((newPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority 10 Fixes NixOS#323624.

winterqt · 2025-08-27T20:48:50Z

Rebased for posterity/the hell of it.

philiptaron

Makes sense to me.

winterqt · 2025-08-27T21:10:33Z

I'm not sure I like that the changed package count is >0, and that it went up from July.

philiptaron · 2025-08-27T21:29:55Z

I'm not sure I like that the changed package count is >0, and that it went up from July.

Here's the link to the specifics.

https://github.com/NixOS/nixpkgs/actions/runs/17278235558/attempts/1#summary-49040691560

`attic-server`

The environments do not match:

- NIX_MAIN_PROGRAM=attic
+ NIX_MAIN_PROGRAM=atticd

`dejavu_fontsEnv`

The environments do not match:

    pkgs=''
- [{"paths":["/nix/store/jm20pdjzh3fg070nfnlw59hbyapf0l60-dejavu-fonts-2.37"],"priority":5}]
+ [{"paths":["/nix/store/jm20pdjzh3fg070nfnlw59hbyapf0l60-dejavu-fonts-2.37"],"priority":10}]
''

`dig`

The environments do not match:

+ NIX_MAIN_PROGRAM=dig

`envision`

Huge diff, concerning, haven't looked at the derivation.

`nixos-install-tools`

Rebuilt because there's a different lib path. This one is OK.

`nixpkgs-manual`

Rebuilt because there's a different lib path. This one is OK.

`pihole`

Rebuilt because dig.

`pihole-web`

Rebuilt because dig

`tests.nixos-functions.nixos-test`

Rebuilt because there's a different lib path. This one is OK.

`vlagent`

The environments do not match:

- NIX_MAIN_PROGRAM=victoria-logs
+ NIX_MAIN_PROGRAM=vlagent

`vmagent`

The environments do not match:

- NIX_MAIN_PROGRAM=victoria-metrics
+ NIX_MAIN_PROGRAM=vmagent

philiptaron · 2025-08-27T21:30:27Z

Of these, only envision looks like a "wat" to me.

winterqt · 2025-08-27T21:33:56Z

Thanks! I’ll take a look at this tomorrow, though it looks like all of these are just making the env more correct! (Besides the scary one, of course.)

(I saw the changed attribute names @philiptaron, but how did you get the nix-diff output?)

philiptaron · 2025-08-27T21:37:51Z

how did you get the nix-diff output

I did a git fetch upstream pull/423615/head:pr-423615/addMetaAttrs to get a local branch, then did a loop over the changed names with a little bash script that did

git checkout pr-423615/addMetaAttrs
DRV_AFTER=$(nix-instantiate -A $name)
git checkout HEAD^1
DRV_BEFORE=$(nix-instantiate -A $name)
nix-diff --line-oriented --color=never $DRV_BEFORE $DRV_AFTER > /tmp/$name.diff

Then I looked at them.

philiptaron · 2025-08-27T21:47:22Z

OK, envision wasn't scary either. Inside of a rootfs-builder derivation, it passed derivations information through. I extracted that with nix derivation show.

diff -U4 <(nix derivation show $drvBefore | jq) <(nix derivation show $drvAfter | jq)

           "paths": [
             "/nix/store/cngwgf1q9jxx6k5dgk9j91kvpqzymdj2-v4l-utils-1.30.1-dev",
             "/nix/store/cngwgf1q9jxx6k5dgk9j91kvpqzymdj2-v4l-utils-1.30.1-dev"
           ],
-          "priority": 5
+          "priority": 10
         },
         {
           "paths": [
             "/nix/store/b5r4kj91isan88a0sff3y5ax26vpxzsf-libxau-1.0.12-dev",

philiptaron

After diving into rebuilds, I believe this is just straightforward goodness.

winterqt · 2025-09-02T19:23:09Z

OK, envision wasn't scary either. Inside of a rootfs-builder derivation, it passed derivations information through. I extracted that with nix derivation show.

diff -U4 <(nix derivation show $drvBefore | jq) <(nix derivation show $drvAfter | jq)

           "paths": [
             "/nix/store/cngwgf1q9jxx6k5dgk9j91kvpqzymdj2-v4l-utils-1.30.1-dev",
             "/nix/store/cngwgf1q9jxx6k5dgk9j91kvpqzymdj2-v4l-utils-1.30.1-dev"
           ],
-          "priority": 5
+          "priority": 10
         },
         {
           "paths": [
             "/nix/store/b5r4kj91isan88a0sff3y5ax26vpxzsf-libxau-1.0.12-dev",

I see this in my diff (expectedly), but doing a nix derivation show /nix/store/gky8cgkrq1z47kazqwkg18v9kh2575vh-envision-2.0.1-fhsenv-rootfs.drv | jq still has the __json field collapsed -- am I missing an easier way to do this than extracting __json and then running that through jq?

philiptaron · 2025-09-02T20:09:24Z

I don't see the __json field in nix derivation show. What version of Nix are you running? I'm on 2.30.2.

winterqt · 2025-09-02T20:46:15Z

I’m on the latest version of Lix. I guess this is something that differs between them!

eclairevoyant · 2025-09-07T12:25:08Z

This broke tesseract.languages and not sure what else.

tesseract: missing languages attr #440907

PatrickDaG · 2025-09-07T13:27:16Z

The reason it broke tesseract is that tesseract is using // to set passthru. Basically pkgs.tesseract // {passthru = {languages = ...;}}.
This PR takes the result from the // and calls overrideAttrs on it which, if I understand it correctly looses these keys introduced by the attr merge.
I think this is just a bad code from in the tesseract package.I'll open a PR to fix it soon.

winterqt added the backport release-25.05 label Jul 8, 2025

nix-owners bot requested review from Artturin, Ericson2314, RossComputerGuy, alyssais, emilazy, philiptaron and reckenrode July 8, 2025 21:15

nixpkgs-ci bot added 6.topic: lib The Nixpkgs function library 10.rebuild-linux: 1-10 This PR causes between 1 and 10 packages to rebuild on Linux. 10.rebuild-darwin: 1-10 This PR causes between 1 and 10 packages to rebuild on Darwin. labels Jul 8, 2025

andrewhamon approved these changes Jul 9, 2025

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nixpkgs-ci bot added the 12.approvals: 1 This PR was reviewed and approved by one person. label Jul 9, 2025

alyssais approved these changes Jul 9, 2025

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nixpkgs-ci bot added 12.approvals: 2 This PR was reviewed and approved by two persons. and removed 12.approvals: 1 This PR was reviewed and approved by one person. labels Jul 9, 2025

winterqt removed the backport release-25.05 label Aug 27, 2025

winterqt force-pushed the push-rzpnszxrqoty branch from 11b3e20 to 2141b4e Compare August 27, 2025 20:41

nixpkgs-ci bot added 10.rebuild-linux: 11-100 This PR causes between 11 and 100 packages to rebuild on Linux. and removed 10.rebuild-linux: 1-10 This PR causes between 1 and 10 packages to rebuild on Linux. labels Aug 27, 2025

philiptaron approved these changes Aug 27, 2025

View reviewed changes

nixpkgs-ci bot added 12.approvals: 3+ This PR was reviewed and approved by three or more persons. and removed 12.approvals: 2 This PR was reviewed and approved by two persons. labels Aug 27, 2025

philiptaron approved these changes Aug 27, 2025

View reviewed changes

winterqt merged commit ba37aa7 into NixOS:master Sep 2, 2025
52 of 53 checks passed

winterqt deleted the push-rzpnszxrqoty branch September 2, 2025 19:23

eclairevoyant mentioned this pull request Sep 7, 2025

tesseract: missing languages attr #440907

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3 tasks

PatrickDaG mentioned this pull request Sep 7, 2025

tesseract: fix passthru override #440938

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attic-server

dejavu_fontsEnv

dig

envision

nixos-install-tools

nixpkgs-manual

pihole

pihole-web

tests.nixos-functions.nixos-test

vlagent

vmagent

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`attic-server`

`dejavu_fontsEnv`

`dig`

`envision`

`nixos-install-tools`

`nixpkgs-manual`

`pihole`

`pihole-web`

`tests.nixos-functions.nixos-test`

`vlagent`

`vmagent`

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