diff --git a/lib/trivial.nix b/lib/trivial.nix index 771a28bc9dad..f0afbf609fca 100644 --- a/lib/trivial.nix +++ b/lib/trivial.nix @@ -12,6 +12,9 @@ let version versionSuffix warn; + inherit (lib) + isString + ; in { ## Simple (higher order) functions @@ -718,98 +721,97 @@ in { importTOML = path: builtins.fromTOML (builtins.readFile path); - ## Warnings - - # See https://github.com/NixOS/nix/issues/749. Eventually we'd like these - # to expand to Nix builtins that carry metadata so that Nix can filter out - # the INFO messages without parsing the message string. - # - # Usage: - # { - # foo = lib.warn "foo is deprecated" oldFoo; - # bar = lib.warnIf (bar == "") "Empty bar is deprecated" bar; - # } - # - # TODO: figure out a clever way to integrate location information from - # something like __unsafeGetAttrPos. - /** - 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` + `warn` *`message`* *`value`* + + Print a warning before returning the second argument. + + See [`builtins.warn`](https://nix.dev/manual/nix/latest/language/builtins.html#builtins-warn) (Nix >= 2.23). + On older versions, the Nix 2.23 behavior is emulated with [`builtins.trace`](https://nix.dev/manual/nix/latest/language/builtins.html#builtins-warn), including the [`NIX_ABORT_ON_WARN`](https://nix.dev/manual/nix/latest/command-ref/conf-file#conf-abort-on-warn) behavior, but not the `nix.conf` setting or command line option. # Inputs - `msg` + *`message`* (String) - : Warning message to print. + : Warning message to print before evaluating *`value`*. - `val` + *`value`* (any value) : Value to return as-is. # Type ``` - string -> a -> a + 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}"; + # Since Nix 2.23, https://github.com/NixOS/nix/pull/10592 + builtins.warn or ( + let mustAbort = lib.elem (builtins.getEnv "NIX_ABORT_ON_WARN") ["1" "true" "yes"]; + in + # Do not eta reduce v, so that we have the same strictness as `builtins.warn`. + msg: v: + # `builtins.warn` requires a string message, so we enforce that in our implementation, so that callers aren't accidentally incompatible with newer Nix versions. + assert isString msg; + if mustAbort + then builtins.trace "evaluation warning: ${msg}" (abort "NIX_ABORT_ON_WARN=true; warnings are treated as unrecoverable errors.") + else builtins.trace "evaluation warning: ${msg}" v + ); /** - Like warn, but only warn when the first argument is `true`. + `warnIf` *`condition`* *`message`* *`value`* + + Like `warn`, but only warn when the first argument is `true`. # Inputs - `cond` + *`condition`* (Boolean) - : 1\. Function argument + : `true` to trigger the warning before continuing with *`value`*. - `msg` + *`message`* (String) - : 2\. Function argument + : Warning message to print before evaluating - `val` + *`value`* (any value) : Value to return as-is. # Type ``` - bool -> string -> a -> a + Bool -> String -> a -> a ``` */ warnIf = cond: msg: if cond then warn msg else x: x; /** - Like warnIf, but negated (warn if the first argument is `false`). + `warnIfNot` *`condition`* *`message`* *`value`* + + Like `warnIf`, but negated: warn if the first argument is `false`. # Inputs - `cond` + *`condition`* - : 1\. Function argument + : `false` to trigger the warning before continuing with `val`. - `msg` + *`message`* - : 2\. Function argument + : Warning message to print before evaluating *`value`*. - `val` + *`value`* : Value to return as-is. # Type ``` - bool -> string -> a -> a + Boolean -> String -> a -> a ``` */ warnIfNot = cond: msg: if cond then x: x else warn msg;