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1# Generators {#sec-generators}
2Generators are functions that create file formats from nix data structures, e. g. for configuration files. There are generators available for: `INI`, `JSON` and `YAML`
3
4All 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.
5
6Generators 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:
7
8```nix
9with lib;
10let
11 customToINI = generators.toINI {
12 # specifies how to format a key/value pair
13 mkKeyValue = generators.mkKeyValueDefault {
14 # specifies the generated string for a subset of nix values
15 mkValueString = v:
16 if v == true then ''"yes"''
17 else if v == false then ''"no"''
18 else if isString v then ''"${v}"''
19 # and delegats all other values to the default generator
20 else generators.mkValueStringDefault {} v;
21 } ":";
22 };
23
24# the INI file can now be given as plain old nix values
25in customToINI {
26 main = {
27 pushinfo = true;
28 autopush = false;
29 host = "localhost";
30 port = 42;
31 };
32 mergetool = {
33 merge = "diff3";
34 };
35}
36```
37
38This will produce the following INI file as nix string:
39
40```INI
41[main]
42autopush:"no"
43host:"localhost"
44port:42
45pushinfo:"yes"
46str\:ange:"very::strange"
47
48[mergetool]
49merge:"diff3"
50```
51
52::: {.note}
53Nix store paths can be converted to strings by enclosing a derivation attribute like so: `"${drv}"`.
54:::
55
56Detailed documentation for each generator can be found in `lib/generators.nix`.