AttributeError seen while running xeus-cpp

[anutosh491]

Hello All,

I maintain xeus-cpp, a Jupyter Kernel to run C++ code.

I am using it with the latest jupyter-server. I didn't see these errors a while back (probably I was using an older version back then) but lately I see this when running it with lab.

Here's a simple readme on how to build the project (shouldn't take more than a couple mins)

This is what I see

I 2025-02-07 10:46:10.431 ServerApp] Kernel started: 18797981-e048-453b-9e6a-12dbb7bb3684
clang version 19.1.6
Target: arm64-apple-darwin23.5.0
Thread model: posix
InstalledDir: /Users/anutosh491/micromamba/envs/xeus-cpp/bin
 "/Users/anutosh491/micromamba/envs/xeus-cpp/bin/xcpp" -cc1 -triple arm64-apple-macosx14.0.0 -Wundef-prefix=TARGET_OS_ -Werror=undef-prefix -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -E -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name "<<< inputs >>>" -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=non-leaf -ffp-contract=on -fno-rounding-math -funwind-tables=1 -target-sdk-version=14.4 -fcompatibility-qualified-id-block-type-checking -fvisibility-inlines-hidden-static-local-var -fbuiltin-headers-in-system-modules -fdefine-target-os-macros -target-cpu apple-m1 -target-feature +zcm -target-feature +zcz -target-feature +v8.4a -target-feature +aes -target-feature +altnzcv -target-feature +ccdp -target-feature +complxnum -target-feature +crc -target-feature +dotprod -target-feature +fp-armv8 -target-feature +fp16fml -target-feature +fptoint -target-feature +fullfp16 -target-feature +jsconv -target-feature +lse -target-feature +neon -target-feature +pauth -target-feature +perfmon -target-feature +predres -target-feature +ras -target-feature +rcpc -target-feature +rdm -target-feature +sb -target-feature +sha2 -target-feature +sha3 -target-feature +specrestrict -target-feature +ssbs -target-abi darwinpcs -debugger-tuning=lldb -fdebug-compilation-dir=/Users/anutosh491/work/xeus-cpp/build5/share/jupyter/kernels/xcpp20 -target-linker-version 951.9 -v -fcoverage-compilation-dir=/Users/anutosh491/work/xeus-cpp/build5/share/jupyter/kernels/xcpp20 -resource-dir /Users/anutosh491/micromamba/envs/xeus-cpp/lib/clang/19 -isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1 -isystem /Library/Developer/CommandLineTools/usr/lib/clang/15.0.0/include -isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include -isystem /Library/Developer/CommandLineTools/usr/include -isystem "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)" -include new -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -I /Users/anutosh491/micromamba/envs/xeus-cpp/include -internal-isystem /Users/anutosh491/micromamba/envs/xeus-cpp/bin/../include/c++/v1 -internal-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/local/include -internal-isystem /Users/anutosh491/micromamba/envs/xeus-cpp/lib/clang/19/include -internal-externc-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include -std=c++20 -fdeprecated-macro -ferror-limit 19 -stack-protector 1 -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fno-implicit-modules -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -fmax-type-align=16 -fcolor-diagnostics -fincremental-extensions -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o - -x c++ "<<< inputs >>>"
clang -cc1 version 19.1.6 based upon LLVM 19.1.6 default target arm64-apple-darwin23.5.0
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/local/include"
ignoring nonexistent directory "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/clang/19/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/Library/Frameworks"
ignoring duplicate directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include"
#include "..." search starts here:
#include <...> search starts here:
 /Users/anutosh491/micromamba/envs/xeus-cpp/include
 /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1
 /Library/Developer/CommandLineTools/usr/lib/clang/15.0.0/include
 /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include
 /Library/Developer/CommandLineTools/usr/include
 /Users/anutosh491/micromamba/envs/xeus-cpp/bin/../include/c++/v1
 /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)
End of search list.
[E 2025-02-07 10:46:11.297 ServerApp] Uncaught exception in ZMQStream callback
    Traceback (most recent call last):
      File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 551, in _run_callback
        f = callback(*args, **kwargs)
            ^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/jupyter_server/services/kernels/kernelmanager.py", line 600, in record_activity
        parent_msg_type = msg.get("parent_header", {}).get("msg_type", None)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    AttributeError: 'NoneType' object has no attribute 'get'
[E 2025-02-07 10:46:11.300 ServerApp] Uncaught exception in zmqstream callback
    Traceback (most recent call last):
      File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 601, in _handle_events
        self._handle_recv()
      File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 630, in _handle_recv
        self._run_callback(callback, msg)
      File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 551, in _run_callback
        f = callback(*args, **kwargs)
            ^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/jupyter_server/services/kernels/kernelmanager.py", line 600, in record_activity
        parent_msg_type = msg.get("parent_header", {}).get("msg_type", None)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    AttributeError: 'NoneType' object has no attribute 'get'
Exception in callback BaseAsyncIOLoop._handle_events(25, 1)
handle: <Handle BaseAsyncIOLoop._handle_events(25, 1)>
Traceback (most recent call last):
  File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/asyncio/events.py", line 88, in _run
    self._context.run(self._callback, *self._args)
  File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/tornado/platform/asyncio.py", line 202, in _handle_events
    handler_func(fileobj, events)
  File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 601, in _handle_events
    self._handle_recv()
  File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 630, in _handle_recv
    self._run_callback(callback, msg)
  File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/zmq/eventloop/zmqstream.py", line 551, in _run_callback
    f = callback(*args, **kwargs)
        ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/anutosh491/micromamba/envs/xeus-cpp/lib/python3.12/site-packages/jupyter_server/services/kernels/kernelmanager.py", line 600, in record_activity
    parent_msg_type = msg.get("parent_header", {}).get("msg_type", None)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'get'
[I 2025-02-07 10:46:11.358 ServerApp] Connecting to kernel 18797981-e048-453b-9e6a-12dbb7bb3684.

[anutosh491]

That being said I obviously don't have issues while running stuff but thought of raising the above error.

[davidbrochart]

Thanks for reporting @anutosh491.
It seems that in your case the parent header is set to None. I don't know if that is valid, or if there shouldn't be any parent_header entry at all. I opened #1498.

[anutosh491]

Thanks for the fix !

[martinRenou]

I'm not sure about the fix, the parent_header should be there as it's part of the protocol https://jupyter-client.readthedocs.io/en/latest/messaging.html#parent-header

As stated in the docs:

_reply messages MUST have a parent_header

So IMO the fix should be in xeus-cpp which MUST provide a parent header in its reply message

[minrk]

It's definitely a bug in xeus-cpp, but clients should handle bugs like this reasonably gracefully, so I think the PR is correct. Plus, the PR is also only fixing the code to do what it already is trying to do (set msg_type to None if parent_header is unavailable), but it previously only handled the case where parent_header is undefined, not defined and None.

[anutosh491]

Thanks .

Yes, I think the Pr is not doing anything unintended and can be moved in.