diff options
Diffstat (limited to 'nixos/doc/manual/development/option-declarations.xml')
| -rw-r--r-- | nixos/doc/manual/development/option-declarations.xml | 48 |
1 files changed, 24 insertions, 24 deletions
diff --git a/nixos/doc/manual/development/option-declarations.xml b/nixos/doc/manual/development/option-declarations.xml index ce432a7fa6ca..d62d0896bb7c 100644 --- a/nixos/doc/manual/development/option-declarations.xml +++ b/nixos/doc/manual/development/option-declarations.xml @@ -65,22 +65,22 @@ options = { </para> -<section xml:id="sec-option-declarations-eot"><title>Extensible Option +<section xml:id="sec-option-declarations-eot"><title>Extensible Option Types</title> - <para>Extensible option types is a feature that allow to extend certain types + <para>Extensible option types is a feature that allow to extend certain types declaration through multiple module files. - This feature only work with a restricted set of types, namely + This feature only work with a restricted set of types, namely <literal>enum</literal> and <literal>submodules</literal> and any composed forms of them.</para> - <para>Extensible option types can be used for <literal>enum</literal> options - that affects multiple modules, or as an alternative to related + <para>Extensible option types can be used for <literal>enum</literal> options + that affects multiple modules, or as an alternative to related <literal>enable</literal> options.</para> <para>As an example, we will take the case of display managers. There is a central display manager module for generic display manager options and a - module file per display manager backend (slim, kdm, gdm ...). + module file per display manager backend (slim, sddm, gdm ...). </para> <para>There are two approach to this module structure: @@ -96,7 +96,7 @@ options = { </para> <para>Both approachs have problems.</para> - + <para>Making backends independent can quickly become hard to manage. For display managers, there can be only one enabled at a time, but the type system can not enforce this restriction as there is no relation between @@ -108,18 +108,18 @@ options = { central module will require to change the central module option every time a new backend is added or removed.</para> - <para>By using extensible option types, it is possible to create a placeholder - option in the central module (<xref linkend='ex-option-declaration-eot-service' - />), and to extend it in each backend module (<xref - linkend='ex-option-declaration-eot-backend-slim' />, <xref - linkend='ex-option-declaration-eot-backend-kdm' />).</para> - + <para>By using extensible option types, it is possible to create a placeholder + option in the central module (<xref linkend='ex-option-declaration-eot-service' + />), and to extend it in each backend module (<xref + linkend='ex-option-declaration-eot-backend-slim' />, <xref + linkend='ex-option-declaration-eot-backend-sddm' />).</para> + <para>As a result, <literal>displayManager.enable</literal> option values can be added without changing the main service module file and the type system automatically enforce that there can only be a single display manager enabled.</para> -<example xml:id='ex-option-declaration-eot-service'><title>Extensible type +<example xml:id='ex-option-declaration-eot-service'><title>Extensible type placeholder in the service module</title> <screen> services.xserver.displayManager.enable = mkOption { @@ -127,29 +127,29 @@ services.xserver.displayManager.enable = mkOption { type = with types; nullOr (enum [ ]); };</screen></example> -<example xml:id='ex-option-declaration-eot-backend-slim'><title>Extending - <literal>services.xserver.displayManager.enable</literal> in the +<example xml:id='ex-option-declaration-eot-backend-slim'><title>Extending + <literal>services.xserver.displayManager.enable</literal> in the <literal>slim</literal> module</title> <screen> services.xserver.displayManager.enable = mkOption { type = with types; nullOr (enum [ "slim" ]); };</screen></example> -<example xml:id='ex-option-declaration-eot-backend-kdm'><title>Extending - <literal>services.foo.backend</literal> in the <literal>kdm</literal> +<example xml:id='ex-option-declaration-eot-backend-sddm'><title>Extending + <literal>services.foo.backend</literal> in the <literal>sddm</literal> module</title> <screen> services.xserver.displayManager.enable = mkOption { - type = with types; nullOr (enum [ "kdm" ]); + type = with types; nullOr (enum [ "sddm" ]); };</screen></example> -<para>The placeholder declaration is a standard <literal>mkOption</literal> - declaration, but it is important that extensible option declarations only use +<para>The placeholder declaration is a standard <literal>mkOption</literal> + declaration, but it is important that extensible option declarations only use the <literal>type</literal> argument.</para> -<para>Extensible option types work with any of the composed variants of - <literal>enum</literal> such as - <literal>with types; nullOr (enum [ "foo" "bar" ])</literal> +<para>Extensible option types work with any of the composed variants of + <literal>enum</literal> such as + <literal>with types; nullOr (enum [ "foo" "bar" ])</literal> or <literal>with types; listOf (enum [ "foo" "bar" ])</literal>.</para> </section> |