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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
9let
10 inherit (lib) generators isString;
11
12 customToINI = generators.toINI {
13 # specifies how to format a key/value pair
14 mkKeyValue = generators.mkKeyValueDefault {
15 # specifies the generated string for a subset of nix values
16 mkValueString = v:
17 if v == true then ''"yes"''
18 else if v == false then ''"no"''
19 else if isString v then ''"${v}"''
20 # and delegates all other values to the default generator
21 else generators.mkValueStringDefault {} v;
22 } ":";
23 };
24
25# the INI file can now be given as plain old nix values
26in customToINI {
27 main = {
28 pushinfo = true;
29 autopush = false;
30 host = "localhost";
31 port = 42;
32 };
33 mergetool = {
34 merge = "diff3";
35 };
36}
37```
38
39This will produce the following INI file as nix string:
40
41```INI
42[main]
43autopush:"no"
44host:"localhost"
45port:42
46pushinfo:"yes"
47str\:ange:"very::strange"
48
49[mergetool]
50merge:"diff3"
51```
52
53::: {.note}
54Nix store paths can be converted to strings by enclosing a derivation attribute like so: `"${drv}"`.
55:::
56
57Detailed documentation for each generator can be found in `lib/generators.nix`.