Repository: spyder-ide/spyder

Issue:
AttributeError when connecting to Jupyter Lab kernel and restarting it there
## Description

### What steps will reproduce the problem?

<!--- You can use Markdown here --->

1. Run Jupyter lab and open ipynb file
2. Run Spyder
3. Connect Spyder console to Jupyter Lab kernel as described here: https://docs.spyder-ide.org/current/panes/ipythonconsole.html#connect-to-a-local-kernel
4. In Jupyter Lab choose "Restart kernel and run all cells"

### Traceback
```python-traceback
Traceback (most recent call last):
  File "C:\Users\XXXX\mambaforge\envs\lab3spyder\Lib\site-packages\spyder\plugins\ipythonconsole\widgets\client.py", line 810, in _finalise_restart
    sw.kernel_manager.autorestart = True
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'autorestart'
```

## Versions

* Spyder version: 5.4.4  (conda)
* Python version: 3.11.4 64-bit
* Qt version: 5.15.6
* PyQt5 version: 5.15.7
* Operating System: Windows-10-10.0.19045-SP0

### Dependencies

```
# Mandatory:
atomicwrites >=1.2.0                                                        :  1.4.1 (OK)
chardet >=2.0.0                                                             :  5.1.0 (OK)
cloudpickle >=0.5.0                                                         :  2.2.1 (OK)
cookiecutter >=1.6.0                                                        :  2.2.3 (OK)
diff_match_patch >=20181111                                                 :  20230430 (OK)
intervaltree >=3.0.2                                                        :  3.1.0 (OK)
IPython >=7.31.1,<9.0.0,!=8.8.0,!=8.9.0,!=8.10.0,!=8.11.0,!=8.12.0,!=8.12.1 :  8.14.0 (OK)
jedi >=0.17.2,<0.19.0                                                       :  0.18.2 (OK)
jellyfish >=0.7                                                             :  1.0.0 (OK)
jsonschema >=3.2.0                                                          :  4.18.4 (OK)
keyring >=17.0.0                                                            :  24.2.0 (OK)
nbconvert >=4.0                                                             :  7.7.2 (OK)
numpydoc >=0.6.0                                                            :  1.5.0 (OK)
paramiko >=2.4.0                                                            :  3.2.0 (OK)
parso >=0.7.0,<0.9.0                                                        :  0.8.3 (OK)
pexpect >=4.4.0                                                             :  4.8.0 (OK)
pickleshare >=0.4                                                           :  0.7.5 (OK)
psutil >=5.3                                                                :  5.9.5 (OK)
pygments >=2.0                                                              :  2.15.1 (OK)
pylint >=2.5.0,<3.0                                                         :  2.17.4 (OK)
pylint_venv >=3.0.2                                                         :  3.0.2 (OK)
pyls_spyder >=0.4.0                                                         :  0.4.0 (OK)
pylsp >=1.7.4,<1.8.0                                                        :  1.7.4 (OK)
pylsp_black >=1.2.0,<3.0.0                                                  :  1.3.0 (OK)
qdarkstyle >=3.0.2,<3.2.0                                                   :  3.1 (OK)
qstylizer >=0.2.2                                                           :  0.2.2 (OK)
qtawesome >=1.2.1                                                           :  1.2.3 (OK)
qtconsole >=5.4.2,<5.5.0                                                    :  5.4.3 (OK)
qtpy >=2.1.0                                                                :  2.3.1 (OK)
rtree >=0.9.7                                                               :  1.0.1 (OK)
setuptools >=49.6.0                                                         :  68.0.0 (OK)
sphinx >=0.6.6                                                              :  7.0.1 (OK)
spyder_kernels >=2.4.4,<2.5.0                                               :  2.4.4 (OK)
textdistance >=4.2.0                                                        :  4.5.0 (OK)
three_merge >=0.1.1                                                         :  0.1.1 (OK)
watchdog >=0.10.3                                                           :  3.0.0 (OK)
zmq >=22.1.0                                                                :  25.1.0 (OK)

# Optional:
cython >=0.21                                                               :  None (NOK)
matplotlib >=3.0.0                                                          :  3.7.2 (OK)
numpy >=1.7                                                                 :  1.25.1 (OK)
pandas >=1.1.1                                                              :  2.0.3 (OK)
scipy >=0.17.0                                                              :  1.11.1 (OK)
sympy >=0.7.3                                                               :  1.12 (OK)

# Spyder plugins:
spyder_line_profiler.spyder.plugin 0.3.2                                    :  0.3.2 (OK)
spyder_notebook.notebookplugin 0.4.1                                        :  0.4.1 (OK)
spyder_terminal.terminalplugin 1.2.2                                        :  1.2.2 (OK)
```



Discussion:
Hey @quctex, thanks for reporting and the clear steps to reproduce this problem (that's very valuable).

We'll take a look at it in our next version (5.5.0), to be released in a couple of months.

Resolving patch:
diff --git a/spyder/plugins/ipythonconsole/widgets/client.py b/spyder/plugins/ipythonconsole/widgets/client.py
--- a/spyder/plugins/ipythonconsole/widgets/client.py
+++ b/spyder/plugins/ipythonconsole/widgets/client.py
@@ -806,9 +806,13 @@ def _finalise_restart(self, reset=False):
                 # Aborting!
                 return
 
-            # Start autorestart mechanism
-            sw.kernel_manager.autorestart = True
-            sw.kernel_manager.start_restarter()
+            # Start autorestart mechanism.
+            # Note: We need to check for kernel_manager in case the kernel is
+            # not managed by us.
+            # Fixes spyder-ide/spyder#21165
+            if sw.kernel_manager:
+                sw.kernel_manager.autorestart = True
+                sw.kernel_manager.start_restarter()
 
             # For spyder-ide/spyder#6235, IPython was changing the
             # setting of %colors on windows by assuming it was using a


Test patch: