Open michaelsproul opened 9 years ago
vcunat
commented
9 years ago These can get very ugly. Right now the evaluator with --show-trace only output
error: value is a string while a set was expectedand no trace at all. It took me hours before I found where the problem was, among the thousands of (texlive) packages.
Mathnerd314
commented
9 years ago Using my latest noisy-nix commits (https://github.com/NixOS/nix/pull/612) the errors show as follows:
$ ~/nix/inst/bin/nix-instantiate . --eval --show-trace --strict -A pkgs.texlive.scheme-full
error: while evaluating the attribute ‘pkgs’ at ~/nixpkgs-test/pkgs/tools/typesetting/tex/texlive-new/default.nix:104:7-104:11:
while evaluating list position ‘10928’:
while evaluating a black hole:
value is a string at ~/nixpkgs-test/pkgs/tools/typesetting/tex/texlive-new/bin.nix:17:15-17:19 while a set was expected at ~/nixpkgs-test/pkgs/tools/typesetting/tex/texlive-new/default.nix:113:15-113:65
$ ~/nix/inst/bin/nix-instantiate --show-trace -E 'with import ./nixos/default.nix { configuration = (a @ {pkgs, ...}: (import /etc/nixos/configuration.nix a) // { environment.systemPackages = [ pkgs.haskellPackages ]; }); }; system'
...
while evaluating the attribute ‘pkgs’ of the derivation ‘system-path’ at ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:38:5-38:9:
while evaluating a black hole at ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:38:5-38:9:
while calling primop toJSON at ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:38:12-41:14:
while evaluating list position ‘250’ at ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:38:12-41:14:
while evaluating the attribute ‘paths’ at ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:39:7-39:12:
while evaluating list position ‘0’ at ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:39:7-39:12:
while calling anonymous function at ~/nixpkgs-test/lib/types.nix:117:14-117:24 from ~/nixpkgs-test/pkgs/build-support/buildenv/default.nix:39:7-39:12:
while evaluating the attribute ‘value’ at ~/nixpkgs-test/lib/types.nix:117:17-117:24:
while evaluating a black hole at ~/nixpkgs-test/lib/types.nix:117:17-117:24:
while calling primop foldl' at ~/nixpkgs-test/lib/modules.nix:314:19-317:43:
while calling anonymous function at ~/nixpkgs-test/lib/modules.nix:314:32-316:96 from ~/nixpkgs-test/lib/modules.nix:314:19-317:43:
while calling ‘check’ at ~/nixpkgs-test/lib/types.nix:97:15-97:49 from ~/nixpkgs-test/lib/modules.nix:315:10-315:30:
while calling ‘isStorePath’ at ~/nixpkgs-test/lib/strings.nix:224:17-224:112 from ~/nixpkgs-test/lib/types.nix:97:36-97:49:
while calling primop substring at ~/nixpkgs-test/lib/strings.nix:224:20-224:55:
while evaluating a black hole at ~/nixpkgs-test/lib/strings.nix:224:20-224:55:
while calling primop toString at ~/nixpkgs-test/lib/strings.nix:224:44-224:54:
cannot coerce a set at (string):1:132-1:152 to a string at ~/nixpkgs-test/lib/strings.nix:224:44-224:54Maybe someone will want to review them...
michaelsproul
commented
9 years ago @Mathnerd314: That looks quite a bit better.
domenkozar
commented
8 years ago 
freddie-freeloader
commented
7 years ago I get this error, for my configuration.nix. I have about 250 values in there. :sob:
It's obviously time to tidy up, but until then:
Are there any debugging tactics to track the problematic value down? :pray:
bjornfor
commented
7 years ago I have use binary search. Comment out half of the file, test, repeat.
freddie-freeloader
commented
7 years ago Reminds me of:
Nix won't be complete until it has static typing.
:wink:
stale[bot]
commented
3 years ago I marked this as stale due to inactivity. → More info
scintill
commented
3 years ago bump to unstalify
milahu
commented
3 years ago Are there any debugging tactics to track the problematic value down?
do a manual stack trace, by inserting dozens of
{
# TRACE
#someAttr = "some value";
someAttr =
lib.traceSeqN 2 { loc = "line 1234"; someAttr = "some value"; }
"some value"
;
}... to get a feel for the program flow
--show-trace more verboseIs your feature request related to a problem? Please describe.
I'm always frustrated when ...
... i have an error in my code, but --show-trace is too short for debugging
Describe the solution you'd like
--show-trace should be more verbose,
it should list all function calls, similar to the stack traces in java or javascript
Describe alternatives you've considered
use lib.traceSeq and friends, to manually locate the error in my code
Additional context
stale[bot]
commented
2 years ago I marked this as stale due to inactivity. → More info
zhaofengli
commented
1 year ago The trace is even worse if you accidentally attempt to access an attset with attrset as a key (e.g., hashes.${stdenv.hostPlatform}):
let
attr = { foo = "bar"; };
key = {};
in attr.${key}$ nix-instantiate --version
nix-instantiate (Nix) 2.13.3
$ nix-instantiate --eval bad-trace.nix --show-trace
error: value is a set while a string was expected
at «none»:0: (source not available)Same with 2.3:
$ nix-instantiate --version
nix-instantiate (Nix) 2.3.16
$ nix-instantiate --eval bad-trace.nix --show-trace
error: value is a set while a string was expected
I found this error quite unhelpful:
The position given for the error is within the NixOS source, so I figured I'd run it again with
--show-trace.Eventually I traced the error to my use of
ghc(a set) rather thanghc.ghc784(a package) inenvironment.systemPackages. The trace fails to mentionghc, its contents or its location in the configuration file (/etc/nixos/configuration:64). Ideally, I would have liked an error like this: