diff --git a/doc/manual/rl-next/better-errors-in-nix-repl.md b/doc/manual/rl-next/better-errors-in-nix-repl.md new file mode 100644 index 000000000..4deaa8c70 --- /dev/null +++ b/doc/manual/rl-next/better-errors-in-nix-repl.md @@ -0,0 +1,40 @@ +--- +synopsis: Concise error printing in `nix repl` +prs: 9928 +--- + +Previously, if an element of a list or attribute set threw an error while +evaluating, `nix repl` would print the entire error (including source location +information) inline. This output was clumsy and difficult to parse: + +``` +nix-repl> { err = builtins.throw "uh oh!"; } +{ err = «error: + … while calling the 'throw' builtin + at «string»:1:9: + 1| { err = builtins.throw "uh oh!"; } + | ^ + + error: uh oh!»; } +``` + +Now, only the error message is displayed, making the output much more readable. +``` +nix-repl> { err = builtins.throw "uh oh!"; } +{ err = «error: uh oh!»; } +``` + +However, if the whole expression being evaluated throws an error, source +locations and (if applicable) a stack trace are printed, just like you'd expect: + +``` +nix-repl> builtins.throw "uh oh!" +error: + … while calling the 'throw' builtin + at «string»:1:1: + 1| builtins.throw "uh oh!" + | ^ + + error: uh oh! +``` +