Add read-only options

These are options that can have only one definition, regardless of
priority.
This commit is contained in:
Eelco Dolstra 2015-07-30 13:36:57 +02:00
parent d61e1b24e6
commit f463d24903
4 changed files with 16 additions and 5 deletions

View file

@ -261,11 +261,16 @@ rec {
evalOptionValue = loc: opt: defs:
let
# Add in the default value for this option, if any.
defs' = (optional (opt ? default)
{ file = head opt.declarations; value = mkOptionDefault opt.default; }) ++ defs;
defs' =
(optional (opt ? default)
{ file = head opt.declarations; value = mkOptionDefault opt.default; }) ++ defs;
# Handle properties, check types, and merge everything together.
res = mergeDefinitions loc opt.type defs';
res =
if opt.readOnly or false && length defs' > 1 then
throw "The option `${showOption loc}' is read-only, but it's set multiple times."
else
mergeDefinitions loc opt.type defs';
# Check whether the option is defined, and apply the apply
# function to the merged value. This allows options to yield a

View file

@ -19,6 +19,7 @@ rec {
, apply ? null # Function that converts the option value to something else.
, internal ? null # Whether the option is for NixOS developers only.
, visible ? null # Whether the option shows up in the manual.
, readOnly ? null # Whether the option can be set only once
, options ? null # Obsolete, used by types.optionSet.
} @ attrs:
attrs // { _type = "option"; };
@ -90,6 +91,7 @@ rec {
declarations = filter (x: x != unknownModule) opt.declarations;
internal = opt.internal or false;
visible = opt.visible or true;
readOnly = opt.readOnly or false;
type = opt.type.name or null;
}
// (if opt ? example then { example = scrubOptionValue opt.example; } else {})

View file

@ -39,6 +39,10 @@
<emphasis>Type:</emphasis>
<xsl:text> </xsl:text>
<xsl:apply-templates select="attr[@name = 'type']" mode="top" />
<xsl:if test="attr[@name = 'readOnly']/bool/@value = 'true'">
<xsl:text> </xsl:text>
<emphasis>(read only)</emphasis>
</xsl:if>
</para>
</xsl:if>

View file

@ -29,7 +29,7 @@ with lib;
};
system.nixosRelease = mkOption {
internal = true;
readOnly = true;
type = types.str;
default = readFile "${toString pkgs.path}/.version";
description = "NixOS release.";
@ -48,7 +48,7 @@ with lib;
};
system.nixosCodeName = mkOption {
internal = true;
readOnly = true;
type = types.str;
description = "NixOS release code name.";
};