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NixOS manual: add module option types doc (#18525)

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Eric Sagnes 2016-09-13 14:04:02 +09:00 committed by Franz Pletz
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commit b32252ddfa
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88
nixos/doc/manual/development/option-declarations.xml
View file

@ -31,9 +31,9 @@ options = {
<varlistentry>
<term><varname>type</varname></term>
<listitem>
<para>The type of the option (see below). It may be omitted,
but that’s not advisable since it may lead to errors that are
hard to diagnose.</para>
<para>The type of the option (see <xref linkend='sec-option-types' />).
It may be omitted, but that’s not advisable since it may lead to errors
that are hard to diagnose.</para>
</listitem>
</varlistentry>
@ -65,86 +65,4 @@ options = {
</para>
<para>Here is a non-exhaustive list of option types:
<variablelist>
<varlistentry>
<term><varname>types.bool</varname></term>
<listitem>
<para>A Boolean.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.int</varname></term>
<listitem>
<para>An integer.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.str</varname></term>
<listitem>
<para>A string.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.lines</varname></term>
<listitem>
<para>A string. If there are multiple definitions, they are
concatenated, with newline characters in between.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.path</varname></term>
<listitem>
<para>A path, defined as anything that, when coerced to a
string, starts with a slash. This includes derivations.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.package</varname></term>
<listitem>
<para>A derivation (such as <literal>pkgs.hello</literal>) or a
store path (such as
<filename>/nix/store/1ifi1cfbfs5iajmvwgrbmrnrw3a147h9-hello-2.10</filename>).</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.listOf</varname> <replaceable>t</replaceable></term>
<listitem>
<para>A list of elements of type <replaceable>t</replaceable>
(e.g., <literal>types.listOf types.str</literal> is a list of
strings). Multiple definitions are concatenated together.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.attrsOf</varname> <replaceable>t</replaceable></term>
<listitem>
<para>A set of elements of type <replaceable>t</replaceable>
(e.g., <literal>types.attrsOf types.int</literal> is a set of
name/value pairs, the values being integers).</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>types.nullOr</varname> <replaceable>t</replaceable></term>
<listitem>
<para>Either the value <literal>null</literal> or something of
type <replaceable>t</replaceable>.</para>
</listitem>
</varlistentry>
</variablelist>
You can also create new types using the function
<varname>mkOptionType</varname>. See
<filename>lib/types.nix</filename> in Nixpkgs for details.</para>
</section>

394
nixos/doc/manual/development/option-types.xml Normal file
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@ -0,0 +1,394 @@
<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-option-types">
<title>Options Types</title>
<para>Option types are a way to put constraints on the values a module option
can take.
Types are also responsible of how values are merged in case of multiple
value definitions.</para>
<section><title>Basic Types</title>
<para>Basic types are the simplest available types in the module system.
Basic types include multiple string types that mainly differ in how
definition merging is handled.</para>
<variablelist>
<varlistentry>
<term><varname>types.bool</varname></term>
<listitem><para>A boolean, its values can be <literal>true</literal> or
<literal>false</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.int</varname></term>
<listitem><para>An integer.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.path</varname></term>
<listitem><para>A filesystem path, defined as anything that when coerced to
a string starts with a slash. Even if derivations can be considered as
path, the more specific <literal>types.package</literal> should be
preferred.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.package</varname></term>
<listitem><para>A derivation or a store path.</para></listitem>
</varlistentry>
</variablelist>
<para>String related types:</para>
<variablelist>
<varlistentry>
<term><varname>types.str</varname></term>
<listitem><para>A string. Multiple definitions cannot be
merged.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.lines</varname></term>
<listitem><para>A string. Multiple definitions are concatenated with a new
line <literal>"\n"</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.commas</varname></term>
<listitem><para>A string. Multiple definitions are concatenated with a comma
<literal>","</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.envVar</varname></term>
<listitem><para>A string. Multiple definitions are concatenated with a
collon <literal>":"</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.separatedString</varname>
<replaceable>sep</replaceable></term>
<listitem><para>A string with a custom separator
<replaceable>sep</replaceable>, e.g. <literal>types.separatedString
"|"</literal>.</para></listitem>
</varlistentry>
</variablelist>
</section>
<section><title>Composed Types</title>
<para>Composed types allow to create complex types by taking another type(s)
or value(s) as parameter(s).
It is possible to compose types multiple times, e.g. <literal>with types;
nullOr (enum [ "left" "right" ])</literal>.</para>
<variablelist>
<varlistentry>
<term><varname>types.listOf</varname> <replaceable>t</replaceable></term>
<listitem><para>A list of <replaceable>t</replaceable> type, e.g.
<literal>types.listOf int</literal>. Multiple definitions are merged
with list concatenation.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.attrsOf</varname> <replaceable>t</replaceable></term>
<listitem><para>An attribute set of where all the values are of
<replaceable>t</replaceable> type. Multiple definitions result in the
joined attribute set.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.loaOf</varname> <replaceable>t</replaceable></term>
<listitem><para>An attribute set or a list of <replaceable>t</replaceable>
type. Multiple definitions are merged according to the
value.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.loeOf</varname> <replaceable>t</replaceable></term>
<listitem><para>A list or an element of <replaceable>t</replaceable> type.
Multiple definitions are merged according to the
values.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.nullOr</varname> <replaceable>t</replaceable></term>
<listitem><para><literal>null</literal> or type
<replaceable>t</replaceable>. Multiple definitions are merged according
to type <replaceable>t</replaceable>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.uniq</varname> <replaceable>t</replaceable></term>
<listitem><para>Ensures that type <replaceable>t</replaceable> cannot be
merged. It is used to ensure option definitions are declared only
once.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.enum</varname> <replaceable>l</replaceable></term>
<listitem><para>One element of the list <replaceable>l</replaceable>, e.g.
<literal>types.enum [ "left" "right" ]</literal>. Multiple definitions
cannot be merged</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.either</varname> <replaceable>t1</replaceable>
<replaceable>t2</replaceable></term>
<listitem><para>Type <replaceable>t1</replaceable> or type
<replaceable>t2</replaceable>, e.g. <literal>with types; either int
str</literal>. Multiple definitions cannot be
merged.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>types.submodule</varname> <replaceable>o</replaceable></term>
<listitem><para>A set of sub options <replaceable>o</replaceable>.
<replaceable>o</replaceable> can be an attribute set or a function
returning an attribute set. Submodules are used in composed types to
create modular options. Submodule are detailed in <xref
linkend='section-option-types-submodule' />.</para></listitem>
</varlistentry>
</variablelist>
</section>
<section xml:id='section-option-types-submodule'><title>Submodule</title>
<para>Submodule is a very powerful type that defines a set of sub-options that
are handled like a separate module.
It is especially interesting when used with composed types like
<literal>attrsOf</literal> or <literal>listOf</literal>.</para>
<para>The submodule type take a parameter <replaceable>o</replaceable>, that
should be a set, or a function returning a set with an
<literal>options</literal> key defining the sub-options.
The option set can be defined directly (<xref linkend='ex-submodule-direct'
/>) or as reference (<xref linkend='ex-submodule-reference' />).</para>
<para>Submodule option definitions are type-checked accordingly to the options
declarations. It is possible to declare submodule options inside a submodule
sub-options for even higher modularity.</para>
<example xml:id='ex-submodule-direct'><title>Directly defined submodule</title>
<screen>
options.mod = mkOption {
name = "mod";
description = "submodule example";
type = with types; listOf (submodule {
options = {
foo = mkOption {
type = int;
};
bar = mkOption {
type = str;
};
};
});
};</screen></example>
<example xml:id='ex-submodule-reference'><title>Submodule defined as a
reference</title>
<screen>
let
modOptions = {
options = {
foo = mkOption {
type = int;
};
bar = mkOption {
type = int;
};
};
};
in
options.mod = mkOption {
description = "submodule example";
type = with types; listOf (submodule modOptions);
};</screen></example>
<section><title>Composed with <literal>listOf</literal></title>
<para>When composed with <literal>listOf</literal>, submodule allows multiple
definitions of the submodule option set.</para>
<example xml:id='ex-submodule-listof-declaration'><title>Declaration of a list
of submodules</title>
<screen>
options.mod = mkOption {
description = "submodule example";
type = with types; listOf (submodule {
options = {
foo = mkOption {
type = int;
};
bar = mkOption {
type = str;
};
};
});
};</screen></example>
<example xml:id='ex-submodule-listof-definition'><title>Definition of a list of
submodules</title>
<screen>
config.mod = [
{ foo = 1; bar = "one"; }
{ foo = 2; bar = "two"; }
];</screen></example>
</section>
<section><title>Composed with <literal>attrsOf</literal></title>
<para>When composed with <literal>attrsOf</literal>, submodule allows multiple
named definitions of the submodule option set.</para>
<example xml:id='ex-submodule-attrsof-declaration'><title>Declaration of
attribute sets of submodules</title>
<screen>
options.mod = mkOption {
description = "submodule example";
type = with types; attrsOf (submodule {
options = {
foo = mkOption {
type = int;
};
bar = mkOption {
type = str;
};
};
});
};</screen></example>
<example xml:id='ex-submodule-attrsof-definition'><title>Declaration of
attribute sets of submodules</title>
<screen>
config.mod.one = { foo = 1; bar = "one"; };
config.mod.two = { foo = 2; bar = "two"; };</screen></example>
</section>
</section>
<section><title>Extending types</title>
<para>Types are mainly characterized by their <literal>check</literal> and
<literal>merge</literal> functions.</para>
<variablelist>
<varlistentry>
<term><varname>check</varname></term>
<listitem><para>The function to type check the value. Takes a value as
parameter and return a boolean.
It is possible to extend a type check with the
<literal>addCheck</literal> function (<xref
linkend='ex-extending-type-check-1' />), or to fully override the
check function (<xref linkend='ex-extending-type-check-2' />).</para>
<example xml:id='ex-extending-type-check-1'><title>Adding a type check</title>
<screen>
byte = mkOption {
description = "An integer between 0 and 255.";
type = addCheck (x: x &gt;= 0 &amp;&amp; x &lt;= 255) types.int;
};</screen></example>
<example xml:id='ex-extending-type-check-2'><title>Overriding a type
check</title>
<screen>
nixThings = mkOption {
description = "words that start with 'nix'";
type = types.str // {
check = (x: lib.hasPrefix "nix" x)
};
};</screen></example>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>merge</varname></term>
<listitem><para>Function to merge the options values when multiple values
are set.
The function takes two parameters, <literal>loc</literal> the option path as a
list of strings, and <literal>defs</literal> the list of defined values as a
list.
It is possible to override a type merge function for custom
needs.</para></listitem>
</varlistentry>
</variablelist>
</section>
<section><title>Custom Types</title>
<para>Custom types can be created with the <literal>mkOptionType</literal>
function.
As type creation includes some more complex topics such as submodule handling,
it is recommended to get familiar with <filename
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/lib/types.nix">types.nix</filename>
code before creating a new type.</para>
<para>The only required parameter is <literal>name</literal>.</para>
<variablelist>
<varlistentry>
<term><varname>name</varname></term>
<listitem><para>A string representation of the type function name, name
usually changes accordingly parameters passed to
types.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>check</varname></term>
<listitem><para>A function to type check the definition value. Takes the
definition value as a parameter and returns a boolean indicating the
type check result, <literal>true</literal> for success and
<literal>false</literal> for failure.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>merge</varname></term>
<listitem><para>A function to merge multiple definitions values. Takes two
parameters:</para>
<variablelist>
<varlistentry>
<term><replaceable>loc</replaceable></term>
<listitem><para>The option path as a list of strings, e.g.
<literal>["boot" "loader "grub"
"enable"]</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><replaceable>defs</replaceable></term>
<listitem><para>The list of sets of defined <literal>value</literal>
and <literal>file</literal> where the value was defined, e.g.
<literal>[ { file = "/foo.nix"; value = 1; } { file = "/bar.nix";
value = 2 } ]</literal>. The <literal>merge</literal> function
should return the merged value or throw an error in case the
values are impossible or not meant to be merged.</para></listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>getSubOptions</varname></term>
<listitem><para>For composed types that can take a submodule as type
parameter, this function generate sub-options documentation. It takes
the current option prefix as a list and return the set of sub-options.
Usually defined in a recursive manner by adding a term to the prefix,
e.g. <literal>prefix: elemType.getSubOptions (prefix ++
[<replaceable>"prefix"</replaceable>])</literal> where
<replaceable>"prefix"</replaceable> is the newly added
prefix.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>getSubModules</varname></term>
<listitem><para>For composed types that can take a submodule as type
parameter, this function should return the type parameters submodules.
If the type parameter is called <literal>elemType</literal>, the
function should just recursively look into submodules by returning
<literal>elemType.getSubModules;</literal>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>substSubModules</varname></term>
<listitem><para>For composed types that can take a submodule as type
parameter, this function can be used to substitute the parameter of a
submodule type. It takes a module as parameter and return the type with
the submodule options substituted. It is usally defined as a type
function call with a recursive call to
<literal>substSubModules</literal>, e.g for a type
<literal>composedType</literal> that take an <literal>elemtype</literal>
type parameter, this function should be defined as <literal>m:
composedType (elemType.substSubModules m)</literal>.</para></listitem>
</varlistentry>
</variablelist>
</section>
</section>

1
nixos/doc/manual/development/writing-modules.xml
View file

@ -176,6 +176,7 @@ in {
</example>
<xi:include href="option-declarations.xml" />
<xi:include href="option-types.xml" />
<xi:include href="option-def.xml" />
<xi:include href="meta-attributes.xml" />