mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-11-22 23:13:19 +00:00
69 lines
2.7 KiB
XML
69 lines
2.7 KiB
XML
|
<section xmlns="http://docbook.org/ns/docbook"
|
||
|
|
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||
|
|
xmlns:xi="http://www.w3.org/2001/XInclude"
|
||
|
|
version="5.0"
|
||
|
|
xml:id="sec-freeform-modules">
|
||
|
|
<title>Freeform modules</title>
|
||
|
|
<para>
|
||
|
|
Freeform modules allow you to define values for option paths that have not been declared explicitly. This can be used to add attribute-specific types to what would otherwise have to be <literal>attrsOf</literal> options in order to accept all attribute names.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
This feature can be enabled by using the attribute <literal>freeformType</literal> to define a freeform type. By doing this, all assignments without an associated option will be merged using the freeform type and combined into the resulting <literal>config</literal> set. Since this feature nullifies name checking for entire option trees, it is only recommended for use in submodules.
|
||
|
|
</para>
|
||
|
|
<example xml:id="ex-freeform-module">
|
||
|
|
<title>Freeform submodule</title>
|
||
|
|
<para>
|
||
|
|
The following shows a submodule assigning a freeform type that allows arbitrary attributes with <literal>str</literal> values below <literal>settings</literal>, but also declares an option for the <literal>settings.port</literal> attribute to have it type-checked and assign a default value. See <xref linkend="ex-settings-typed-attrs"/> for a more complete example.
|
||
|
|
</para>
|
||
|
|
<programlisting>
|
||
|
|
{ lib, config, ... }: {
|
||
|
|
|
||
|
|
options.settings = lib.mkOption {
|
||
|
|
type = lib.types.submodule {
|
||
|
|
|
||
|
|
freeformType = with lib.types; attrsOf str;
|
||
|
|
|
||
|
|
# We want this attribute to be checked for the correct type
|
||
|
|
options.port = lib.mkOption {
|
||
|
|
type = lib.types.port;
|
||
|
|
# Declaring the option also allows defining a default value
|
||
|
|
default = 8080;
|
||
|
|
};
|
||
|
|
|
||
|
|
};
|
||
|
|
};
|
||
|
|
}
|
||
|
|
</programlisting>
|
||
|
|
<para>
|
||
|
|
And the following shows what such a module then allows
|
||
|
|
</para>
|
||
|
|
<programlisting>
|
||
|
|
{
|
||
|
|
# Not a declared option, but the freeform type allows this
|
||
|
|
settings.logLevel = "debug";
|
||
|
|
|
||
|
|
# Not allowed because the the freeform type only allows strings
|
||
|
|
# settings.enable = true;
|
||
|
|
|
||
|
|
# Allowed because there is a port option declared
|
||
|
|
settings.port = 80;
|
||
|
|
|
||
|
|
# Not allowed because the port option doesn't allow strings
|
||
|
|
# settings.port = "443";
|
||
|
|
}
|
||
|
|
</programlisting>
|
||
|
|
</example>
|
||
|
|
<note>
|
||
|
|
<para>
|
||
|
|
Freeform attributes cannot depend on other attributes of the same set without infinite recursion:
|
||
|
|
<programlisting>
|
||
|
|
{
|
||
|
|
# This throws infinite recursion encountered
|
||
|
|
settings.logLevel = lib.mkIf (config.settings.port == 80) "debug";
|
||
|
|
}
|
||
|
|
</programlisting>
|
||
|
|
To prevent this, declare options for all attributes that need to depend on others. For above example this means to declare <literal>logLevel</literal> to be an option.
|
||
|
|
</para>
|
||
|
|
</note>
|
||
|
|
</section>
|