lix/tests/lang/eval-okay-attrs2.nix
Eelco Dolstra 8a1ab709a4 * New builtin functions builtins.{hasAttr, getAttr} to check for
attribute existence and to return an attribute from an attribute
  set, respectively.  Example: `hasAttr "foo" {foo = 1;}'.  They
  differ from the `?' and `.' operators in that the attribute name is
  an arbitrary expression.  (NIX-61)
2006-09-22 14:31:55 +00:00

11 lines
231 B
Nix

let {
as = { x = 123; y = 456; } // { z = 789; } // { z = 987; };
A = "a";
Z = "z";
body = if builtins.hasAttr A as
then builtins.getAttr A as
else assert builtins.hasAttr Z as; builtins.getAttr Z as;
}