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Merge pull request #11455 from zagy/add/hasAttrByPath

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add helper to lib/attrsets: hasAttrByPath
This commit is contained in:
Eelco Dolstra 2015-12-16 15:46:12 +01:00
commit 064ceef792
2 changed files with 21 additions and 0 deletions
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11
lib/attrsets.nix
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@ -23,6 +23,17 @@ rec {
then attrByPath (tail attrPath) default e.${attr}
else default;
/* Return if an attribute from nested attribute set exists.
For instance ["x" "y"] applied to some set e returns true, if e.x.y exists. False
is returned otherwise. */
hasAttrByPath = attrPath: e:
let attr = head attrPath;
in
if attrPath == [] then true
else if e ? ${attr}
then hasAttrByPath (tail attrPath) e.${attr}
else false;
/* Return nested attribute set in which an attribute is set. For instance
["x" "y"] applied with some value v returns `x.y = v;' */

10
lib/tests.nix
View File

@ -120,4 +120,14 @@ runTests {
expected = { success = false; value = false; };
};
testHasAttrByPathTrue = {
expr = hasAttrByPath ["a" "b"] { a = { b = "yey"; }; };
expected = true;
};
testHasAttrByPathFalse = {
expr = hasAttrByPath ["a" "b"] { a = { c = "yey"; }; };
expected = false;
};
}