kernel "hangs" after error

[haraldschilly]

we've seen an issue, where evaluating a cell with the content x (i.e. undefined variable or whatever) causes an error message and no further communication is possible. is this a known problem?

/cc @DrXyzzy

[olexandr-konovalov]

This was known, and I believe this has been fixed. Which version of GAP and packages do you have? Attached is what works for me.

[haraldschilly]

Attached is my screenshot, from a similar session. It's compiled on ubuntu 18.04, everything as how it comes from the tarball provided on the website. I don't know how to also list the version numbers of relevant packages, though. However, here is how it looks to me, with a freshly-restarted kernel:

[olexandr-konovalov]

@haraldschilly thank you, that's really helpful. I can reproduce exactly this session with exactly the same issue on a mac. The same issue is happening when using mybinder from https://github.com/alex-konovalov/gap-teaching (currently using the master branch of GAP).

BTW, you can get versions of packages as follows:

gap> GAPInfo.PackagesInfo.jupyterkernel[1].Version;
"0.99999"

with the packagename there in lowercase. PackageInfo("JupyterKernel"); returns all meta-data about the package, and is not case-sensitive.

[DrXyzzy]

Thanks. I was using the following and getting info from the generated log file

JUPYTER_LogProtocol("gaplog.out");

[haraldschilly]

Ok, glad you could reproduce it … and thank you for the version info command, our versions of jupyterkernel are the same.

[markuspf]

The problem is in GAP's error handling: gap-system/gap#2487,
I'll try and see whether I can do some wrangling to get it to not crash...

[olexandr-konovalov]

Since gap-system/gap#2487 is closed, it may be worth testing if the GAP Jupyter kernel works better with the GAP master branch...

[olexandr-konovalov]

In GAP 4.11.1, crucial part for reproducing the error above is to enter x without a semicolon. With semicolon, it does not hang.