Using overrideScope' on Qt leaves dependency on old qmake

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1

This is possibly a bug but I could also be doing this totally wrong!

I’m trying to apply a custom patch to Qt using overrideScope'. This seems to mostly work except that the qmake that’s actually used to build Qt isn’t seeing the override - it’s built with a qtbase that isn’t patched.

Here’s a demo:

$ nix repl
Welcome to Nix version 2.2.2. Type :? for help.

nix-repl> :l
Added 10566 variables.

nix-repl> pkgs.qt512.qmake # old qmake
«derivation /nix/store/89lj77ypxadp06n76pr6338aiw8wd3a5-hook.drv»

nix-repl> qt_override = pkgs.qt512.overrideScope' (
  self: super: { qtbase = super.qtbase.overrideAttrs (o: {
    patches = o.patches ++ [./some.patch]; }); })

nix-repl> qt_override.qtsvg
«derivation /nix/store/j4nbjjzphqsb9b27nra78i1iwmjf8c8q-qtsvg-5.12.0.drv»

# Grep shows we are still depending on old qmake
$ nix-store --query -R /nix/store/j4nbjjzphqsb9b27nra78i1iwmjf8c8q-qtsvg-5.12.0.drv | grep /nix/store/89lj77ypxadp06n76pr6338aiw8wd3a5-hook.drv
/nix/store/89lj77ypxadp06n76pr6338aiw8wd3a5-hook.drv

I ran this example against a local (slightly stale) nixpkgs but have subsequently verified on the 19.03 channel and nixpkgs master.

2

This is very old and this won’t apply to versions of Qt in modern nixpkgs, but just in case someone is building old software:

The problem here is that qmake comes from a makeSetupHook inside the Qt packages scope that isn’t overrideable. So, overriding the scope will override all the actual modules, which are created with mkDerivation, but will not override qmake.