57 lines
2 KiB
Markdown
57 lines
2 KiB
Markdown
# Generators {#sec-generators}
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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`
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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.
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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:
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```nix
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let
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inherit (lib) generators isString;
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customToINI = generators.toINI {
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# specifies how to format a key/value pair
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mkKeyValue = generators.mkKeyValueDefault {
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# specifies the generated string for a subset of nix values
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mkValueString = v:
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if v == true then ''"yes"''
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else if v == false then ''"no"''
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else if isString v then ''"${v}"''
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# and delegates all other values to the default generator
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else generators.mkValueStringDefault {} v;
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} ":";
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};
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# the INI file can now be given as plain old nix values
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in customToINI {
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main = {
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pushinfo = true;
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autopush = false;
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host = "localhost";
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port = 42;
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};
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mergetool = {
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merge = "diff3";
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};
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}
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```
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This will produce the following INI file as nix string:
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```INI
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[main]
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autopush:"no"
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host:"localhost"
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port:42
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pushinfo:"yes"
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str\:ange:"very::strange"
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[mergetool]
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merge:"diff3"
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```
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::: {.note}
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Nix store paths can be converted to strings by enclosing a derivation attribute like so: `"${drv}"`.
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:::
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Detailed documentation for each generator can be found in `lib/generators.nix`.
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