lib.attrsets.longestValidPathPrefix

Return the longest prefix of an attribute path that refers to an existing attribute in a nesting of attribute sets.

Can be used after mapAttrsRecursiveCond to apply a condition, although this will evaluate the predicate function on sibling attributes as well.

Note that the empty attribute path is valid for all values, so this function only throws an exception if any of its inputs does.

Laws:

1. attrsets.longestValidPathPrefix [] x == []
   

2. hasAttrByPath (attrsets.longestValidPathPrefix p x) x == true
   

Inputs

attrPath

A list of strings representing the longest possible path that may be returned.

v

The nested attribute set to check.

Type

attrsets.longestValidPathPrefix :: [String] -> Value -> [String]

Examples

x = { a = { b = 3; }; }
attrsets.longestValidPathPrefix ["a" "b" "c"] x
=> ["a" "b"]
attrsets.longestValidPathPrefix ["a"] x
=> ["a"]
attrsets.longestValidPathPrefix ["z" "z"] x
=> []
attrsets.longestValidPathPrefix ["z" "z"] (throw "no need")
=> []