diff options
Diffstat (limited to 'doc/functions/generators.section.md')
-rw-r--r-- | doc/functions/generators.section.md | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/doc/functions/generators.section.md b/doc/functions/generators.section.md new file mode 100644 index 00000000000..d54e5027c79 --- /dev/null +++ b/doc/functions/generators.section.md @@ -0,0 +1,56 @@ +# 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 ''"${v}"'' + # and delegats all other values to the default generator + else generators.mkValueStringDefault {} v; + } ":"; + }; + +# the INI file can now be given as plain old nix values +in customToINI { + main = { + pushinfo = true; + autopush = false; + host = "localhost"; + port = 42; + }; + mergetool = { + merge = "diff3"; + }; +} +``` + +This will produce the following INI file as nix string: + +```INI +[main] +autopush:"no" +host:"localhost" +port:42 +pushinfo:"yes" +str\:ange:"very::strange" + +[mergetool] +merge:"diff3" +``` + +::: {.note} +Nix store paths can be converted to strings by enclosing a derivation attribute like so: `"${drv}"`. +::: + +Detailed documentation for each generator can be found in `lib/generators.nix`. |