nh displays duplicate error messages during build failures while nixos-build shows single message

[cig0]

Hello, I initially reported this issue in the nh issue tracker (link: nix-community/nh#223) but was redirected here as it appears to be a NOM bug.

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When a build error occurs using nh, I've observed that the error message is printed twice in the output. The same build configuration produces only a single error message when using nixos-build.

Steps to reproduce:

• Using a flake configuration that triggers a build error
• Running the build with nh
• Running the same build with nixos-build

Expected behavior:

Error messages should be displayed once, similar to nixos-build

Actual behavior:

The exact error message appears twice in the output when using nh

Additional context:

• I've observed this behavior across multiple flakes, including my own and two other flakes from different repositories, suggesting this isn't specific to my configuration.
• If this is unexpected behavior, I can provide my flake configuration for further investigation.

Thanks!

[maralorn]

This is currently intended behavior. I realize that it looks stupid in this case, but in larger builds, especially with --keep-going the error can be harder to see. So just disabling the error summary is not really something I am inclined to do.

I am open to discussing this, though.

[cig0]

Hi @maralorn, thanks for clarifying it. Would showing a single copy of the error message when there's only one error to report work for you?

[maralorn]

I mean then the question is: which one?^^ I’d prefer to collect errors in the box. But for the others it’s hard to predict whether there are more to come.

Generally I would like to not print the errors in the log, but sometimes the errors become to many or to big and get truncated, then you loose information when they are not in the log. Maybe we can do something about that?

[cig0]

I mean then the question is: which one?^^

I'm sorry, I don't follow you! If there's only one error message shown twice (like in my OP), does it matter which of the two outputs to show?

Generally I would like to not print the errors in the log, but sometimes the errors become to many or to big and get truncated, then you loose information when they are not in the log. Maybe we can do something about that?

What about having a flag to print error logs out to an external file? (I'm speaking out of my convenience here; I don't know how difficult that would be to implement)

[cig0]

I mean then the question is: which one?^^

I'm sorry, I don't follow you! If there's only one error message shown twice (like in my OP), does it matter which of the two outputs to show?

Generally I would like to not print the errors in the log, but sometimes the errors become to many or to big and get truncated, then you loose information when they are not in the log. Maybe we can do something about that?

What about having a flag to print error logs out to an external file? (I'm speaking out of my convenience here; I don't know how difficult that would be to implement)

Actually, stdout would be the right way; from there, anyone needing a hard copy can pipe them to a file.