mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-11-24 16:03:23 +00:00
57 lines
2.0 KiB
Markdown
57 lines
2.0 KiB
Markdown
# Generators {#sec-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:
|
||
|
||
```nix
|
||
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 ''"${v}"''
|
||
# and delegates all other values to the default generator
|
||
else generators.mkValueStringDefault {} v;
|
||
} ":";
|
||
};
|
||
|
||
# the INI file can now be given as plain old nix values
|
||
in customToINI {
|
||
main = {
|
||
pushinfo = true;
|
||
autopush = false;
|
||
host = "localhost";
|
||
port = 42;
|
||
};
|
||
mergetool = {
|
||
merge = "diff3";
|
||
};
|
||
}
|
||
```
|
||
|
||
This will produce the following INI file as nix string:
|
||
|
||
```INI
|
||
[main]
|
||
autopush:"no"
|
||
host:"localhost"
|
||
port:42
|
||
pushinfo:"yes"
|
||
str\:ange:"very::strange"
|
||
|
||
[mergetool]
|
||
merge:"diff3"
|
||
```
|
||
|
||
::: {.note}
|
||
Nix store paths can be converted to strings by enclosing a derivation attribute like so: `"${drv}"`.
|
||
:::
|
||
|
||
Detailed documentation for each generator can be found in `lib/generators.nix`.
|