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nixpkgs docs: document optionalAttrs

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(cherry picked from commit e0c6981d19)
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Graham Christensen 2018-10-12 15:42:39 -04:00
parent 3736fcdc64
commit 8b02f90f3a
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53
doc/functions/library/attrsets.xml
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@ -1300,4 +1300,57 @@ lib.attrsets.isDerivation "foobar"
</varlistentry>
</variablelist>
</section>
<section xml:id="function-library-lib.attrsets.optionalAttrs">
<title><function>lib.attrsets.optionalAttrs</function></title>
<subtitle><literal>optionalAttrs :: Bool -> AttrSet</literal>
</subtitle>
<xi:include href="./locations.xml" xpointer="lib.attrsets.optionalAttrs" />
<para>
Conditionally return an attribute set or an empty attribute set.
</para>
<variablelist>
<varlistentry>
<term>
<varname>cond</varname>
</term>
<listitem>
<para>
Condition under which the <varname>as</varname> attribute set is
returned.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>as</varname>
</term>
<listitem>
<para>
The attribute set to return if <varname>cond</varname> is true.
</para>
</listitem>
</varlistentry>
</variablelist>
<example xml:id="function-library-lib.attrsets.optionalAttrs-example-true">
<title>Return the provided attribute set when <varname>cond</varname> is true</title>
<programlisting><![CDATA[
lib.attrsets.optionalAttrs true { my = "set"; }
=> { my = "set"; }
]]></programlisting>
</example>
<example xml:id="function-library-lib.attrsets.optionalAttrs-example-false">
<title>Return an empty attribute set when <varname>cond</varname> is false</title>
<programlisting><![CDATA[
lib.attrsets.optionalAttrs false { my = "set"; }
=> { }
]]></programlisting>
</example>
</section>
</section>