Generators
Generators are functions that create file formats from nix data structures,
e. g. for configuration files. There are generators available for:
INI, JSON and YAML
All generators follow a similar call interface: generatorName
configFunctions data, where configFunctions is an
attrset of user-defined functions that format nested parts of the content.
They each have common defaults, so often they do not need to be set manually.
An example is mkSectionName ? (name: libStr.escape [ "[" "]" ]
name) from the INI generator. It receives the name
of a section and sanitizes it. The default mkSectionName
escapes [ and ] with a backslash.
Generators can be fine-tuned to produce exactly the file format required by
your application/service. One example is an INI-file format which uses
: as separator, the strings
"yes"/"no" as boolean values and
requires all string values to be quoted:
with lib;
let
customToINI = generators.toINI {
# specifies how to format a key/value pair
mkKeyValue = generators.mkKeyValueDefault {
# specifies the generated string for a subset of nix values
mkValueString = v:
if v == true then ''"yes"''
else if v == false then ''"no"''
else if isString v then ''"${v}"''
# and delegats all other values to the default generator
else generators.mkValueStringDefault {} v;
} ":";
};
# the INI file can now be given as plain old nix values
in customToINI {
main = {
pushinfo = true;
autopush = false;
host = "localhost";
port = 42;
};
mergetool = {
merge = "diff3";
};
}
This will produce the following INI file as nix string:
[main]
autopush:"no"
host:"localhost"
port:42
pushinfo:"yes"
str\:ange:"very::strange"
[mergetool]
merge:"diff3"
Nix store paths can be converted to strings by enclosing a derivation
attribute like so: "${drv}".
Detailed documentation for each generator can be found in
lib/generators.nix.