mkPackageOption pkgs "name" { default = [ "path" "in" "pkgs" ]; example = "literal example"; }
```

Creates an Option attribute set for an option that specifies the package a module should use for some purpose.

**Note**: You should make package options for your modules, where applicable. While one can always overwrite a specific package throughout nixpkgs by using [nixpkgs overlays](https://nixos.org/manual/nixpkgs/stable/#chap-overlays), they slow down nixpkgs evaluation significantly and are harder to debug when issues arise.

The package is specified in the third argument under `default` as a list of strings
representing its attribute path in nixpkgs (or another package set).
Because of this, you need to pass nixpkgs itself (or a subset) as the first argument.

The second argument may be either a string or a list of strings.
It provides the display name of the package in the description of the generated option
(using only the last element if the passed value is a list)
and serves as the fallback value for the `default` argument.

To include extra information in the description, pass `extraDescription` to
append arbitrary text to the generated description.
You can also pass an `example` value, either a literal string or an attribute path.

The default argument can be omitted if the provided name is
an attribute of pkgs (if name is a string) or a
valid attribute path in pkgs (if name is a list).

If you wish to explicitly provide no default, pass `null` as `default`.

[]{#ex-options-declarations-util-mkPackageOption}
Examples:

::: {#ex-options-declarations-util-mkPackageOption-hello .example}
### Simple `mkPackageOption` usage
```nix
lib.mkPackageOption pkgs "hello" { }
# is like
lib.mkOption {
  type = lib.types.package;
  default = pkgs.hello;
  defaultText = lib.literalExpression "pkgs.hello";
  description = "The hello package to use.";
}
```
:::

::: {#ex-options-declarations-util-mkPackageOption-ghc .example}
### `mkPackageOption` with explicit default and example
```nix
lib.mkPackageOption pkgs "GHC" {
  default = [ "ghc" ];
  example = "pkgs.haskell.packages.ghc92.ghc.withPackages (hkgs: [ hkgs.primes ])";
}
# is like
lib.mkOption {
  type = lib.types.package;
  default = pkgs.ghc;
  defaultText = lib.literalExpression "pkgs.ghc";
  example = lib.literalExpression "pkgs.haskell.packages.ghc92.ghc.withPackages (hkgs: [ hkgs.primes ])";
  description = "The GHC package to use.";
}
```
:::

::: {#ex-options-declarations-util-mkPackageOption-extraDescription .example}
### `mkPackageOption` with additional description text
```nix
mkPackageOption pkgs [ "python312Packages" "torch" ] {
  extraDescription = "This is an example and doesn't actually do anything.";
}
# is like
lib.mkOption {
  type = lib.types.package;
  default = pkgs.python312Packages.torch;
  defaultText = lib.literalExpression "pkgs.python312Packages.torch";
  description = "The pytorch package to use. This is an example and doesn't actually do anything.";
}
```
:::

## Extensible Option Types {#sec-option-declarations-eot}

Extensible option types is a feature that allows to extend certain types
declaration through multiple module files. This feature only work with a