WebIO not detected in Jupyter when using custom sysimage

[oschulz]

I get the error "WebIO not detected." when using WebIO+Interact in Jupyter with a custom Julia system image that includes WebIO (generated via PackageCompiler).

This happens with both JupyterLab and Jupyter-Notebook. But the problem only occurs if WebIO (and Interact) are part of the sysimage. Using a custom sysimage including other files works fine, the error only occurs if WebIO is included in the image. So when I first build the sysimage and then add WebIO and Interact to the project, everything works as expected.

System info:

julia> versioninfo()
Julia Version 1.7.0-rc2
Commit f23fc0d27a (2021-10-20 12:45 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, skylake)

(@v1.7) pkg> st WebIO Interact
      Status `/opt/julia-1.7/local/share/julia/environments/v1.7/Project.toml`
  [c601a237] Interact v0.10.4
  [0f1e0344] WebIO v0.8.16

[twavv]

The sysimage thing really shouldn't be the issue since the "WebIO not detected" message comes from the frontend (the Jupyter extension) which isn't (shouldn't?) be affected by the sysimage.

[oschulz]

I have to admit that I have no idea how/why - but I've tested this several times: The "WebIO not detected" error occurs as soon as I bake WebIO itself into the system image, and only then.

[habemus-papadum]

I can confirm I also see this behavior -- I get not detected once WebIO gets baked into the sysimage. Like @oschulz, I'm not sure why it is happening.