nushell: Structured settings

[JoaquinTrinanes]

Description

Closes #5527 (but it should be fixed on new nushell versions regardless of this PR if programs.nushell.configFile is set in an adequate way)

• After Load default_env.nu/default_config.nu before user env.nu/config.nu nushell/nushell#14249 nushell loads the default config before the user config, removing the need to explicitly set it.
• After Nushell generator #5905, it is now possible to convert structured nix values into nushell code.

Hence, this PR reintroduces the programs.nushell.settings option. It then flattens the config and assigns each value to $env.config. The flattening step is done to avoid overwriting previously defined config values (otherwise, completions.quick = true would become $env.config.completions = { quick: true }, deleting all other completions config).

{
  show_banner = false;
  completions.external = {
    enable = true;
    max_results = 200;
  };
}

becomes

$env.config.completions.external.enable = true
$env.config.completions.external.max_results = 200
$env.config.show_banner = false

One thing I'm wondering is if the code should have a special cases for lists/records, and append/merge them instead of assigning them. This could be implemented on a followup PR if we see the need 🤔

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

Maintainer CC

@Philipp-M @aidalgol

[rycee]

An alternative implementation that I personally find slightly more readable and is potentially a bit more efficient since it avoids the intermediate attribute set (although I imagine you'll need many settings for it to be noticeable 🙂).

I haven't tested it beyond the test case and feel free to reject the suggestion if you prefer the original version:

Suggested change

	(let
	flattenSettings = settings:
	let
	unravel = prefixes: value:
	if (lib.isAttrs value && !isNushellInline value) then
	lib.flatten
	(map (key: unravel (prefixes ++ [ key ]) value.${key})
	(builtins.attrNames value))
	else
	lib.nameValuePair (lib.concatStringsSep "." prefixes) value;
	in lib.listToAttrs (unravel [ ] settings);
	flattenedSettings = flattenSettings cfg.settings;
	in lib.mkIf (cfg.settings != { }) (lib.concatLines (lib.mapAttrsToList
	(key: value: "$env.config.${key} = ${toNushell { } value}")
	flattenedSettings)))
	(let
	flattenSettings = let
	joinDot = a: b: "${if a == "" then "" else "${a}."}${b}";
	unravel = prefix: value:
	if lib.isAttrs value && !isNushellInline value then
	lib.concatMap (key: unravel (joinDot prefix key) value.${key})
	(builtins.attrNames value)
	else
	[ (lib.nameValuePair prefix value) ];
	in unravel "";
	mkLine = { name, value }: ''
	$env.config.${name} = ${toNushell { } value}
	'';
	settingsLines =
	lib.concatMapStrings mkLine (flattenSettings cfg.settings);
	in lib.mkIf (cfg.settings != { }) settingsLines)

[JoaquinTrinanes]

Ooh thanks! I prefer your implementation, it's way easier to understand 😄