Re:The Curse of NixOS
by mindslight on Tuesday January 25, 2022 @10:48AM
(#30073122)
Ah, I had forgotten `override` is easy. Rereading that page I still don't get the difference between `overrideAttrs` and `overrideDerivation`. `overrideAttrs` is newer and preferred, yet it doesn't spell out where you cannot use it and have to fall back to `overrideDeriviation`. And looking through my Nix code I've got various uses of `overrideDerivation`, which most likely means I tried `overrideAttrs` only to have it not work, so I tried the "deprecated" version and it did.
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I think the manual is intetionally flying over `overrideDerivation` because it shouldn't be used. To understand the difference you'd have to know that `stdenv.mkDerivation` is a library function that wraps the Nix primitive `builtins.derivation`, which is what actually makes a derivation.
`overrideAttrs` changes the arguments of the former, while `overrideDerivation` changes the arguments of the latter. The reason is it's "deprecated" is that it forces a full evaluation of `stdenv.mkDerivation` before it can continue and it override the lower-level derivation, so some niceties that Nixpkgs provides don't work with it.
Re:The Curse of NixOS
by mindslight on Tuesday January 25, 2022 @05:10PM
(#30078830)
Thank you for explaining the difference! I think the manual would be better served by an explanation like that, rather than just implying that `overrideDerivation` may still need to be used for some unspecified reason. I'll have to revisit my uses and see why `overrideAttr` didn't work for me. Perhaps I was using the wrong argument name.