522 lines
20 KiB
XML
522 lines
20 KiB
XML
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="sec-option-types">
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<title>Options Types</title>
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<para>Option types are a way to put constraints on the values a module option
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can take.
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Types are also responsible of how values are merged in case of multiple
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value definitions.</para>
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<section><title>Basic Types</title>
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<para>Basic types are the simplest available types in the module system.
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Basic types include multiple string types that mainly differ in how
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definition merging is handled.</para>
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<variablelist>
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<varlistentry>
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<term><varname>types.bool</varname></term>
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<listitem><para>A boolean, its values can be <literal>true</literal> or
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<literal>false</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.path</varname></term>
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<listitem><para>A filesystem path, defined as anything that when coerced to
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a string starts with a slash. Even if derivations can be considered as
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path, the more specific <literal>types.package</literal> should be
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preferred.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.package</varname></term>
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<listitem><para>A derivation or a store path.</para></listitem>
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</varlistentry>
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</variablelist>
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<para>Integer-related types:</para>
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<variablelist>
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<varlistentry>
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<term><varname>types.int</varname></term>
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<listitem><para>A signed integer.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>types.ints.{s8, s16, s32}</varname>
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</term>
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<listitem>
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<para>Signed integers with a fixed length (8, 16 or 32 bits).
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They go from
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<inlineequation><mathphrase>−2<superscript>n</superscript>/2</mathphrase>
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</inlineequation> to <inlineequation>
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<mathphrase>2<superscript>n</superscript>/2−1</mathphrase>
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</inlineequation>
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respectively (e.g. <literal>−128</literal> to <literal>127</literal>
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for 8 bits).
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>types.ints.unsigned</varname>
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</term>
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<listitem><para>An unsigned integer (that is >= 0).
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>types.ints.{u8, u16, u32}</varname>
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</term>
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<listitem>
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<para>Unsigned integers with a fixed length (8, 16 or 32 bits).
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They go from
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<inlineequation><mathphrase>0</mathphrase></inlineequation> to <inlineequation>
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<mathphrase>2<superscript>n</superscript>−1</mathphrase>
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</inlineequation>
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respectively (e.g. <literal>0</literal> to <literal>255</literal>
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for 8 bits).
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>types.ints.positive</varname>
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</term>
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<listitem><para>A positive integer (that is > 0).
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</para></listitem>
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</varlistentry>
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</variablelist>
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<para>String-related types:</para>
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<variablelist>
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<varlistentry>
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<term><varname>types.str</varname></term>
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<listitem><para>A string. Multiple definitions cannot be
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merged.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.lines</varname></term>
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<listitem><para>A string. Multiple definitions are concatenated with a new
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line <literal>"\n"</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.commas</varname></term>
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<listitem><para>A string. Multiple definitions are concatenated with a comma
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<literal>","</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.envVar</varname></term>
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<listitem><para>A string. Multiple definitions are concatenated with a
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collon <literal>":"</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.strMatching</varname></term>
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<listitem><para>A string matching a specific regular expression. Multiple
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definitions cannot be merged. The regular expression is processed using
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<literal>builtins.match</literal>.</para></listitem>
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</varlistentry>
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</variablelist>
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</section>
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<section><title>Value Types</title>
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<para>Value types are types that take a value parameter.</para>
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<variablelist>
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<varlistentry>
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<term><varname>types.enum</varname> <replaceable>l</replaceable></term>
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<listitem><para>One element of the list <replaceable>l</replaceable>, e.g.
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<literal>types.enum [ "left" "right" ]</literal>. Multiple definitions
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cannot be merged.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.separatedString</varname>
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<replaceable>sep</replaceable></term>
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<listitem><para>A string with a custom separator
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<replaceable>sep</replaceable>, e.g. <literal>types.separatedString
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"|"</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>types.ints.between</varname>
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<replaceable>lowest</replaceable>
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<replaceable>highest</replaceable>
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</term>
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<listitem><para>An integer between <replaceable>lowest</replaceable>
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and <replaceable>highest</replaceable> (both inclusive).
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Useful for creating types like <literal>types.port</literal>.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.submodule</varname> <replaceable>o</replaceable></term>
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<listitem><para>A set of sub options <replaceable>o</replaceable>.
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<replaceable>o</replaceable> can be an attribute set or a function
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returning an attribute set. Submodules are used in composed types to
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create modular options. Submodule are detailed in <xref
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linkend='section-option-types-submodule' />.</para></listitem>
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</varlistentry>
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</variablelist>
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</section>
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<section><title>Composed Types</title>
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<para>Composed types are types that take a type as parameter. <literal>listOf
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int</literal> and <literal>either int str</literal> are examples of
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composed types.</para>
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<variablelist>
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<varlistentry>
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<term><varname>types.listOf</varname> <replaceable>t</replaceable></term>
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<listitem><para>A list of <replaceable>t</replaceable> type, e.g.
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<literal>types.listOf int</literal>. Multiple definitions are merged
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with list concatenation.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.attrsOf</varname> <replaceable>t</replaceable></term>
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<listitem><para>An attribute set of where all the values are of
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<replaceable>t</replaceable> type. Multiple definitions result in the
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joined attribute set.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.loaOf</varname> <replaceable>t</replaceable></term>
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<listitem><para>An attribute set or a list of <replaceable>t</replaceable>
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type. Multiple definitions are merged according to the
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value.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.nullOr</varname> <replaceable>t</replaceable></term>
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<listitem><para><literal>null</literal> or type
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<replaceable>t</replaceable>. Multiple definitions are merged according
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to type <replaceable>t</replaceable>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.uniq</varname> <replaceable>t</replaceable></term>
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<listitem><para>Ensures that type <replaceable>t</replaceable> cannot be
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merged. It is used to ensure option definitions are declared only
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once.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.either</varname> <replaceable>t1</replaceable>
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<replaceable>t2</replaceable></term>
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<listitem><para>Type <replaceable>t1</replaceable> or type
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<replaceable>t2</replaceable>, e.g. <literal>with types; either int
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str</literal>. Multiple definitions cannot be
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merged.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>types.coercedTo</varname> <replaceable>from</replaceable>
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<replaceable>f</replaceable> <replaceable>to</replaceable></term>
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<listitem><para>Type <replaceable>to</replaceable> or type
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<replaceable>from</replaceable> which will be coerced to
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type <replaceable>to</replaceable> using function
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<replaceable>f</replaceable> which takes an argument of type
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<replaceable>from</replaceable> and return a value of type
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<replaceable>to</replaceable>. Can be used to preserve backwards
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compatibility of an option if its type was changed.</para></listitem>
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</varlistentry>
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</variablelist>
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</section>
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<section xml:id='section-option-types-submodule'><title>Submodule</title>
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<para><literal>submodule</literal> is a very powerful type that defines a set
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of sub-options that are handled like a separate module.</para>
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<para>It takes a parameter <replaceable>o</replaceable>, that should be a set,
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or a function returning a set with an <literal>options</literal> key
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defining the sub-options.
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Submodule option definitions are type-checked accordingly to the
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<literal>options</literal> declarations.
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Of course, you can nest submodule option definitons for even higher
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modularity.</para>
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<para>The option set can be defined directly
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(<xref linkend='ex-submodule-direct' />) or as reference
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(<xref linkend='ex-submodule-reference' />).</para>
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<example xml:id='ex-submodule-direct'><title>Directly defined submodule</title>
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<screen>
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options.mod = mkOption {
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description = "submodule example";
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type = with types; submodule {
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options = {
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foo = mkOption {
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type = int;
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};
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bar = mkOption {
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type = str;
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};
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};
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};
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};</screen></example>
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<example xml:id='ex-submodule-reference'><title>Submodule defined as a
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reference</title>
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<screen>
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let
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modOptions = {
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options = {
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foo = mkOption {
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type = int;
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};
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bar = mkOption {
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type = int;
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};
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};
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};
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in
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options.mod = mkOption {
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description = "submodule example";
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type = with types; submodule modOptions;
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};</screen></example>
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<para>The <literal>submodule</literal> type is especially interesting when
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used with composed types like <literal>attrsOf</literal> or
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<literal>listOf</literal>.
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When composed with <literal>listOf</literal>
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(<xref linkend='ex-submodule-listof-declaration' />),
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<literal>submodule</literal> allows multiple definitions of the submodule
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option set (<xref linkend='ex-submodule-listof-definition' />).</para>
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<example xml:id='ex-submodule-listof-declaration'><title>Declaration of a list
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of submodules</title>
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<screen>
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options.mod = mkOption {
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description = "submodule example";
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type = with types; listOf (submodule {
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options = {
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foo = mkOption {
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type = int;
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};
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bar = mkOption {
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type = str;
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};
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};
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});
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};</screen></example>
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<example xml:id='ex-submodule-listof-definition'><title>Definition of a list of
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submodules</title>
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<screen>
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config.mod = [
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{ foo = 1; bar = "one"; }
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{ foo = 2; bar = "two"; }
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];</screen></example>
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<para>When composed with <literal>attrsOf</literal>
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(<xref linkend='ex-submodule-attrsof-declaration' />),
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<literal>submodule</literal> allows multiple named definitions of the
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submodule option set (<xref linkend='ex-submodule-attrsof-definition' />).
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</para>
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<example xml:id='ex-submodule-attrsof-declaration'><title>Declaration of
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attribute sets of submodules</title>
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<screen>
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options.mod = mkOption {
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description = "submodule example";
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type = with types; attrsOf (submodule {
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options = {
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foo = mkOption {
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type = int;
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};
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bar = mkOption {
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type = str;
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};
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};
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});
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};</screen></example>
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<example xml:id='ex-submodule-attrsof-definition'><title>Declaration of
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attribute sets of submodules</title>
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<screen>
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config.mod.one = { foo = 1; bar = "one"; };
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config.mod.two = { foo = 2; bar = "two"; };</screen></example>
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</section>
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<section><title>Extending types</title>
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<para>Types are mainly characterized by their <literal>check</literal> and
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<literal>merge</literal> functions.</para>
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<variablelist>
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<varlistentry>
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<term><varname>check</varname></term>
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<listitem><para>The function to type check the value. Takes a value as
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parameter and return a boolean.
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It is possible to extend a type check with the
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<literal>addCheck</literal> function (<xref
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linkend='ex-extending-type-check-1' />), or to fully override the
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check function (<xref linkend='ex-extending-type-check-2' />).</para>
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<example xml:id='ex-extending-type-check-1'><title>Adding a type check</title>
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<screen>
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byte = mkOption {
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description = "An integer between 0 and 255.";
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type = addCheck types.int (x: x >= 0 && x <= 255);
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};</screen></example>
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<example xml:id='ex-extending-type-check-2'><title>Overriding a type
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check</title>
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<screen>
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nixThings = mkOption {
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description = "words that start with 'nix'";
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type = types.str // {
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check = (x: lib.hasPrefix "nix" x)
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};
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};</screen></example>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>merge</varname></term>
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<listitem><para>Function to merge the options values when multiple values
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are set.
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The function takes two parameters, <literal>loc</literal> the option path as a
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list of strings, and <literal>defs</literal> the list of defined values as a
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list.
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It is possible to override a type merge function for custom
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needs.</para></listitem>
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</varlistentry>
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</variablelist>
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</section>
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<section><title>Custom Types</title>
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<para>Custom types can be created with the <literal>mkOptionType</literal>
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function.
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As type creation includes some more complex topics such as submodule handling,
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it is recommended to get familiar with <filename
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/lib/types.nix">types.nix</filename>
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code before creating a new type.</para>
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<para>The only required parameter is <literal>name</literal>.</para>
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<variablelist>
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<varlistentry>
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<term><varname>name</varname></term>
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<listitem><para>A string representation of the type function
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name.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>definition</varname></term>
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<listitem><para>Description of the type used in documentation. Give
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information of the type and any of its arguments.</para></listitem>
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||
</varlistentry>
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||
<varlistentry>
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<term><varname>check</varname></term>
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||
<listitem><para>A function to type check the definition value. Takes the
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||
definition value as a parameter and returns a boolean indicating the
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||
type check result, <literal>true</literal> for success and
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||
<literal>false</literal> for failure.</para></listitem>
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||
</varlistentry>
|
||
<varlistentry>
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||
<term><varname>merge</varname></term>
|
||
<listitem><para>A function to merge multiple definitions values. Takes two
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parameters:</para>
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||
<variablelist>
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||
<varlistentry>
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||
<term><replaceable>loc</replaceable></term>
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||
<listitem><para>The option path as a list of strings, e.g.
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||
<literal>["boot" "loader "grub"
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"enable"]</literal>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
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||
<term><replaceable>defs</replaceable></term>
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||
<listitem><para>The list of sets of defined <literal>value</literal>
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||
and <literal>file</literal> where the value was defined, e.g.
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||
<literal>[ { file = "/foo.nix"; value = 1; } { file = "/bar.nix";
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||
value = 2 } ]</literal>. The <literal>merge</literal> function
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||
should return the merged value or throw an error in case the
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||
values are impossible or not meant to be merged.</para></listitem>
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||
</varlistentry>
|
||
</variablelist>
|
||
</listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>getSubOptions</varname></term>
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||
<listitem><para>For composed types that can take a submodule as type
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||
parameter, this function generate sub-options documentation. It takes
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||
the current option prefix as a list and return the set of sub-options.
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||
Usually defined in a recursive manner by adding a term to the prefix,
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||
e.g. <literal>prefix: elemType.getSubOptions (prefix ++
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||
[<replaceable>"prefix"</replaceable>])</literal> where
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||
<replaceable>"prefix"</replaceable> is the newly added
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||
prefix.</para></listitem>
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||
</varlistentry>
|
||
<varlistentry>
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||
<term><varname>getSubModules</varname></term>
|
||
<listitem><para>For composed types that can take a submodule as type
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||
parameter, this function should return the type parameters submodules.
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||
If the type parameter is called <literal>elemType</literal>, the
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||
function should just recursively look into submodules by returning
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||
<literal>elemType.getSubModules;</literal>.</para></listitem>
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||
</varlistentry>
|
||
<varlistentry>
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||
<term><varname>substSubModules</varname></term>
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||
<listitem><para>For composed types that can take a submodule as type
|
||
parameter, this function can be used to substitute the parameter of a
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||
submodule type. It takes a module as parameter and return the type with
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||
the submodule options substituted. It is usually defined as a type
|
||
function call with a recursive call to
|
||
<literal>substSubModules</literal>, e.g for a type
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||
<literal>composedType</literal> that take an <literal>elemtype</literal>
|
||
type parameter, this function should be defined as <literal>m:
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||
composedType (elemType.substSubModules m)</literal>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>typeMerge</varname></term>
|
||
<listitem><para>A function to merge multiple type declarations. Takes the
|
||
type to merge <literal>functor</literal> as parameter. A
|
||
<literal>null</literal> return value means that type cannot be
|
||
merged.</para>
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><replaceable>f</replaceable></term>
|
||
<listitem><para>The type to merge
|
||
<literal>functor</literal>.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
<para>Note: There is a generic <literal>defaultTypeMerge</literal> that
|
||
work with most of value and composed types.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>functor</varname></term>
|
||
<listitem><para>An attribute set representing the type. It is used for type
|
||
operations and has the following keys:</para>
|
||
<variablelist>
|
||
<varlistentry>
|
||
<term><varname>type</varname></term>
|
||
<listitem><para>The type function.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>wrapped</varname></term>
|
||
<listitem><para>Holds the type parameter for composed types.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>payload</varname></term>
|
||
<listitem><para>Holds the value parameter for value types.
|
||
The types that have a <literal>payload</literal> are the
|
||
<literal>enum</literal>, <literal>separatedString</literal> and
|
||
<literal>submodule</literal> types.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>binOp</varname></term>
|
||
<listitem><para>A binary operation that can merge the payloads of two
|
||
same types. Defined as a function that take two payloads as
|
||
parameters and return the payloads merged.</para></listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
</listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
</section>
|
||
</section>
|