nt/nib/std/attrs.nix
2025-12-13 21:59:28 +10:00

101 lines
2.2 KiB
Nix

{lists}: rec {
nameValuePair = name: value: {inherit name value;};
listToAttrsIdentity = values:
builtins.listToAttrs (
builtins.map
(x: nameValuePair x x)
values
);
/**
Generate an attribute set by mapping a function over a list of
attribute names.
# Inputs
`names`
: Names of values in the resulting attribute set.
`f`
: A function, given the name of the attribute, returns the attribute's value.
# Type
```
genAttrs :: [ String ] -> (String -> Any) -> AttrSet
```
# Examples
:::{.example}
## `lib.attrsets.genAttrs` usage example
```nix
genAttrs [ "foo" "bar" ] (name: "x_" + name)
=> { foo = "x_foo"; bar = "x_bar"; }
```
:::
*/
genAttrs = names: f: genAttrs' names (n: nameValuePair n (f n));
/**
Like `genAttrs`, but allows the name of each attribute to be specified in addition to the value.
The applied function should return both the new name and value as a `nameValuePair`.
::: {.warning}
In case of attribute name collision the first entry determines the value,
all subsequent conflicting entries for the same name are silently ignored.
:::
# Inputs
`xs`
: A list of strings `s` used as generator.
`f`
: A function, given a string `s` from the list `xs`, returns a new `nameValuePair`.
# Type
```
genAttrs' :: [ Any ] -> (Any -> { name :: String; value :: Any; }) -> AttrSet
```
# Examples
:::{.example}
## `lib.attrsets.genAttrs'` usage example
```nix
genAttrs' [ "foo" "bar" ] (s: nameValuePair ("x_" + s) ("y_" + s))
=> { x_foo = "y_foo"; x_bar = "y_bar"; }
```
:::
*/
genAttrs' = xs: f: builtins.listToAttrs (map f xs);
mapAttrsRecursiveCond = cond: f: set: let
recurse = path:
builtins.mapAttrs (
name: value:
if builtins.isAttrs value && cond value
then recurse (path ++ [name]) value
else f (path ++ [name]) value
);
in
recurse [] set;
mapAttrsRecursive = f: set: mapAttrsRecursiveCond (as: true) f set;
# form: attrValueAt :: xs -> path -> value
# given path as a list of strings, return that value of an
# attribute set at that path
attrValueAt = lists.foldl (l: r:
if l != null && builtins.hasAttr r l
then l.${r}
else null);
}