Unverified Commit 4df10deb authored by Naïm Favier's avatar Naïm Favier
Browse files

lib/customisation.overrideDerivation: propagate evaluation condition 

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`.
parent 2c83122c

doc/using/overrides.chapter.md

+1 −1
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@@ -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.

lib/customisation.nix

+9 −1
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@@ -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 {};

      }

pkgs/servers/x11/xorg/overrides.nix

+1 −2
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@@ -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"