lix/doc/manual/rl-next/builtins-warn.md

synopsis, cls, category, credits

synopsis	cls	category	credits
Add `builtins.warn` for emitting warnings from Nix code	2248	Features	milibopp Qyriad

Lix now has a builtin function for emitting warnings. Like builtins.trace, it takes two arguments: the message to emit, and the expression to return. Unlike builtins.trace, builtins.warn requires the first argument — the message — to be a string. In the future we may extend builtins.warn to accept a more structured API.

To go along with this, we also have two new config settings:

• debugger-on-warn, which, when used with --debugger, makes builtins.warn also function like builtins.break.
• abort-on-warn, which aborts evaluation entirely after the warning is emitted.