Introduction to Denix Options

Denix options are a wrapper for lib.mkOption. This means that any Denix option can be created using the standard lib.mkOption, and using Denix options is optional.

Why use Denix options?

Using lib.mkOption can be cumbersome, and writing something like this every time:

lib.mkOption {type = lib.types.listOf lib.types.str; default = [];}

is inconvenient, especially when options are used extensively in your configuration. Instead, you can write something more concise:

delib.listOfOption delib.str []

Thus, instead of creating an option by specifying all parameters, you can use Denix functions for more readable and cleaner code.

Working Principle

Functions related to options are divided into four main types:

Creating an Option with Type N

• *Option <default> - for example, strOption "foo".
• *OfOption <secondType> <default> - for example, listOfOption str ["foo" "bar"].
• *ToOption <secondType> <default> - for example, lambdaToOption int (x: 123).

Adding Type N to Option Type X

• allow* <option> - for example, allowStr ....
• allow*Of <secondType> <option> - for example, allowListOf str ....
• allow*To <secondType> <option> - for example, allowLambdaTo int ....

Directly Modifying the Attribute Set of an Option

• noDefault <option> - removes the default attribute from the option. It is rarely used since options without a default value are uncommon.
• readOnly <option> - adds the readOnly attribute with the value true.
• apply <option> <apply> - adds the apply attribute with the value passed to this function.
• description <option> <description> - adds the description attribute with the given value.

Generating Specific Options

• singleEnableOption <default> {name, ...} - creates an attribute set using the expression delib.setAttrByStrPath "${name}.enable" (boolOption default). This is commonly used in delib.module :: options with its passed arguments, so you can simply write:

options = delib.singleEnableOption <default>;

The list of current options can be found in the source code: github:yunfachi/denix?path=lib/options.nix

Examples

Denix	lib.mkOption
portOption 22	mkOption {type = types.port; default = 22;}
noDefault (portOption null)	mkOption {type = types.port;}
allowNull (portOption null)	mkOption {type = types.nullOr types.port; default = null;}
allowStr (portOption "22")	mkOption {type = types.strOr types.port; default = "22";}
listOfOption port []	mkOption {type = types.listOf types.port; default = [];}
readOnly (noDefault (portOption null))	mkOption {type = types.port; readOnly = true;}
singleEnableOption true {name = "git";}	git.enable = mkEnableOption "git" // {default = true;}

(Usually {name = "git";} is not required, as this function is mainly used in delib.module :: options)