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Diffstat (limited to 'lib/attrsets.nix')
-rw-r--r-- | lib/attrsets.nix | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/lib/attrsets.nix b/lib/attrsets.nix index 77e36d3271f7..09a2efa40a25 100644 --- a/lib/attrsets.nix +++ b/lib/attrsets.nix @@ -542,6 +542,36 @@ rec { attrs: map (name: f name attrs.${name}) (attrNames attrs); + /* + Deconstruct an attrset to a list of name-value pairs as expected by [`builtins.listToAttrs`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-listToAttrs). + Each element of the resulting list is an attribute set with these attributes: + - `name` (string): The name of the attribute + - `value` (any): The value of the attribute + + The following is always true: + ```nix + builtins.listToAttrs (attrsToList attrs) == attrs + ``` + + :::{.warning} + The opposite is not always true. In general expect that + ```nix + attrsToList (builtins.listToAttrs list) != list + ``` + + This is because the `listToAttrs` removes duplicate names and doesn't preserve the order of the list. + ::: + + Example: + attrsToList { foo = 1; bar = "asdf"; } + => [ { name = "bar"; value = "asdf"; } { name = "foo"; value = 1; } ] + + Type: + attrsToList :: AttrSet -> [ { name :: String; value :: Any; } ] + + */ + attrsToList = mapAttrsToList nameValuePair; + /* Like `mapAttrs`, except that it recursively applies itself to the *leaf* attributes of a potentially-nested attribute set: |