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lib/customisation.overrideDerivation: propagate evaluation condition

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The new derivation should evaluate only if the old derivation does.

Sadly this means that the old derivation cannot depend on the new one
any more, which was used by xorgserver on Darwin. But this is not a
problem as `overrideAttrs` can (and should) usually be used instead.

This change allowed catching an invalid `meta.platforms` in the linux_rpi
kernels, which use `overrideDerivation`.
This commit is contained in:
Naïm Favier 2022-12-06 18:51:29 +01:00
parent 2c83122c18
commit 4df10debe7
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GPG key ID: 95AFCE8211908325
3 changed files with 11 additions and 4 deletions
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2
doc/using/overrides.chapter.md
View file

@ -63,7 +63,7 @@ You should prefer `overrideAttrs` in almost all cases, see its documentation for
:::
::: {.warning}
Do not use this function in Nixpkgs as it evaluates a Derivation before modifying it, which breaks package abstraction and removes error-checking of function arguments. In addition, this evaluation-per-function application incurs a performance penalty, which can become a problem if many overrides are used. It is only intended for ad-hoc customisation, such as in `~/.config/nixpkgs/config.nix`.
Do not use this function in Nixpkgs as it evaluates a derivation before modifying it, which breaks package abstraction. In addition, this evaluation-per-function application incurs a performance penalty, which can become a problem if many overrides are used. It is only intended for ad-hoc customisation, such as in `~/.config/nixpkgs/config.nix`.
:::
The function `overrideDerivation` creates a new derivation based on an existing one by overriding the original's attributes with the attribute set produced by the specified function. This function is available on all derivations defined using the `makeOverridable` function. Most standard derivation-producing functions, such as `stdenv.mkDerivation`, are defined using this function, which means most packages in the nixpkgs expression, `pkgs`, have this function.

10
lib/customisation.nix
View file

@ -27,11 +27,19 @@ rec {
For another application, see build-support/vm, where this
function is used to build arbitrary derivations inside a QEMU
virtual machine.
Note that in order to preserve evaluation errors, the new derivation's
outPath depends on the old one's, which means that this function cannot
be used in circular situations when the old derivation also depends on the
new one.
You should in general prefer `drv.overrideAttrs` over this function;
see the nixpkgs manual for more information on overriding.
*/
overrideDerivation = drv: f:
let
newDrv = derivation (drv.drvAttrs // (f drv));
in lib.flip (extendDerivation true) newDrv (
in lib.flip (extendDerivation (builtins.seq drv.drvPath true)) newDrv (
{ meta = drv.meta or {};
passthru = if drv ? passthru then drv.passthru else {};
}

3
pkgs/servers/x11/xorg/overrides.nix
View file

@ -11,7 +11,6 @@
let
inherit (stdenv) isDarwin;
inherit (lib) overrideDerivation;
malloc0ReturnsNullCrossFlag = lib.optional
(stdenv.hostPlatform != stdenv.buildPlatform)
@ -761,7 +760,7 @@ self: super:
];
# XQuartz requires two compilations: the first to get X / XQuartz,
# and the second to get Xvfb, Xnest, etc.
darwinOtherX = overrideDerivation xorgserver (oldAttrs: {
darwinOtherX = xorgserver.overrideAttrs (oldAttrs: {
configureFlags = oldAttrs.configureFlags ++ [
"--disable-xquartz"
"--enable-xorg"