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lib.warn: Add NIX_ABORT_ON_WARN for call traces #140763

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Merged
roberth merged 1 commit into from
Oct 13, 2021
Merged

lib.warn: Add NIX_ABORT_ON_WARN for call traces #140763

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21 changes: 20 additions & 1 deletion lib/trivial.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -303,7 +303,26 @@ rec {
# TODO: figure out a clever way to integrate location information from
# something like __unsafeGetAttrPos.

warn = msg: builtins.trace "warning: ${msg}";
/*
Print a warning before returning the second argument. This function behaves
like `builtins.trace`, but requires a string message and formats it as a
warning, including the `warning: ` prefix.

To get a call stack trace and abort evaluation, set the environment variable
`NIX_ABORT_ON_WARN=true` and set the Nix options `--option pure-eval false --show-trace`

Type: string -> a -> a
*/
warn =
if lib.elem (builtins.getEnv "NIX_ABORT_ON_WARN") ["1" "true" "yes"]
then msg: builtins.trace "warning: ${msg}" (abort "NIX_ABORT_ON_WARN=true; warnings are treated as unrecoverable errors.")
else msg: builtins.trace "warning: ${msg}";

/*
Like warn, but only warn when the first argument is `true`.

Type: bool -> string -> a -> a
*/
warnIf = cond: msg: if cond then warn msg else id;

info = msg: builtins.trace "INFO: ${msg}";
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