mirror of
https://github.com/ryan4yin/nixos-and-flakes-book.git
synced 2024-11-28 19:14:12 +01:00
234c4efcf1
Nix already produces a warning that future versions will require using '--file' parameter to import files. This commit future-proofs the book for when the '--file' parameter is mandatory.
68 lines
3.0 KiB
Markdown
68 lines
3.0 KiB
Markdown
# Overriding
|
|
|
|
In Nix, you can customize Nix packages in `pkgs` by using the `override` function, which allows you to define custom build parameters and returns a new derivation with the overridden values. Let's take a look at an example:
|
|
|
|
```nix
|
|
pkgs.fcitx5-rime.override { rimeDataPkgs = [ ./rime-data-flypy ]; }
|
|
```
|
|
|
|
In the above example, we override the `rimeDataPkgs` parameter of the `fcitx5-rime` derivation to use a custom package called `rime-data-flypy`. This creates a new derivation where `rimeDataPkgs` is overridden, while other parameters remain unchanged.
|
|
|
|
To find out which parameters of a specific package can be overridden, there are a couple of approaches you can follow:
|
|
|
|
1. Check the source code of the package in the Nixpkgs repository on GitHub, such as [`fcitx5-rime.nix`](https://github.com/NixOS/nixpkgs/blob/e4246ae1e7f78b7087dce9c9da10d28d3725025f/pkgs/tools/inputmethods/fcitx5/fcitx5-rime.nix). Make sure to select the appropriate branch, such as `nixos-unstable`, if you are using that branch.
|
|
2. Use the `nix repl -f '<nixpkgs>'` command to open a Nix REPL and then enter `:e pkgs.fcitx5-rime`. This opens the source code of the package in your default editor, where you can see all the parameters of the package. To learn the basic usage of `nix repl`, you can type `:?` to see the help information.
|
|
|
|
By using these methods, you can discover the input parameters of a package and determine which ones can be modified using `override`.
|
|
|
|
For example, let's take a look at the source code of [pkgs.hello](https://github.com/NixOS/nixpkgs/blob/nixos-23.05/pkgs/applications/misc/hello/default.nix):
|
|
|
|
```nix
|
|
{ callPackage
|
|
, lib
|
|
, stdenv
|
|
, fetchurl
|
|
, nixos
|
|
, testers
|
|
, hello
|
|
}:
|
|
|
|
stdenv.mkDerivation (finalAttrs: {
|
|
pname = "hello";
|
|
version = "2.12.1";
|
|
|
|
src = fetchurl {
|
|
url = "mirror://gnu/hello/hello-${finalAttrs.version}.tar.gz";
|
|
sha256 = "sha256-jZkUKv2SV28wsM18tCqNxoCZmLxdYH2Idh9RLibH2yA=";
|
|
};
|
|
|
|
doCheck = true;
|
|
|
|
# ...
|
|
})
|
|
```
|
|
|
|
In this example, the attributes `pname`, `version`, `src`, and `doCheck` can all be overridden using `overrideAttrs`. For instance:
|
|
|
|
```nix
|
|
helloWithDebug = pkgs.hello.overrideAttrs (finalAttrs: previousAttrs: {
|
|
doCheck = false;
|
|
});
|
|
```
|
|
|
|
In the above code, we use `overrideAttrs` to override the `doCheck` attribute, while leaving other attributes unchanged.
|
|
|
|
You can also override some default attributes defined in `stdenv.mkDerivation` using `overrideAttrs`. For example:
|
|
|
|
```nix
|
|
helloWithDebug = pkgs.hello.overrideAttrs (finalAttrs: previousAttrs: {
|
|
separateDebugInfo = true;
|
|
});
|
|
```
|
|
|
|
In this case, we override the `separateDebugInfo` attribute, which is defined in `stdenv.mkDerivation`, rather than in the source code of `hello`.
|
|
|
|
To see all the attributes defined in `stdenv.mkDerivation`, you can check its source code by using `nix repl -f '<nixpkgs>'` and entering `:e stdenv.mkDerivation`.
|
|
|
|
This will open the source code in your default editor. If you're new to using `nix repl`, you can type `:?` to see the help information.
|