PR: Fix errors when getting Matplotlib backend in the kernel (IPython console)

spyder/plugins/ipythonconsole/tests/test_ipythonconsole.py

@@ -1923,7 +1923,6 @@ def test_pdb_comprehension_namespace(ipyconsole, qtbot, tmpdir):
 
 @flaky(max_runs=10)
 @pytest.mark.auto_backend
-@pytest.mark.skipif(os.name == 'nt', reason="Fails on windows")
 def test_restart_interactive_backend(ipyconsole, qtbot):
     """
     Test that we ask for a restart or not after switching to different
@@ -1936,7 +1935,8 @@ def test_restart_interactive_backend(ipyconsole, qtbot):
 
     # This is necessary to test no spurious messages are printed to the console
     shell.clear_console()
-    qtbot.waitUntil(lambda: '\nIn [2]: ' == shell._control.toPlainText())
+    empty_console_text = '\n\nIn [2]: ' if os.name == "nt" else '\nIn [2]: '
+    qtbot.waitUntil(lambda: empty_console_text == shell._control.toPlainText())
 
     # Switch to the tk backend
     ipyconsole.set_conf('pylab/backend', 'tk')
@@ -1967,7 +1967,7 @@ def test_restart_interactive_backend(ipyconsole, qtbot):
     assert bool(os.environ.get('BACKEND_REQUIRE_RESTART'))
 
     # Check we no spurious messages are shown before the restart below
-    assert "\nIn [2]: " == shell._control.toPlainText()
+    assert empty_console_text == shell._control.toPlainText()
 
     # Restart kernel to check if the new interactive backend is set
     ipyconsole.restart_kernel()

spyder/plugins/ipythonconsole/utils/kernel_handler.py

@@ -201,8 +201,14 @@ def connect_(self):
         self._shellwidget_connected = True
         # Emit signal in case the connection is already made
         if self.connection_state in [
-                KernelConnectionState.IpykernelReady,
-                KernelConnectionState.SpyderKernelReady]:
+            KernelConnectionState.IpykernelReady,
+            KernelConnectionState.SpyderKernelReady
+        ]:
+            # This is necessary for systems in which the kernel takes too much
+            # time to start because in that case its heartbeat is not detected
+            # as beating at this point.
+            # Fixes spyder-ide/spyder#22179
+            self.kernel_client.hb_channel._beating = True
             self.sig_kernel_is_ready.emit()
         elif self.connection_state == KernelConnectionState.Error:
             self.sig_kernel_connection_error.emit()
@@ -274,6 +280,11 @@ def handle_comm_ready(self):
             KernelConnectionState.SpyderKernelWaitComm,
             KernelConnectionState.Crashed
         ]:
+            # This is necessary for systems in which the kernel takes too much
+            # time to start because in that case its heartbeat is not detected
+            # as beating at this point.
+            # Fixes spyder-ide/spyder#22179
+            self.kernel_client.hb_channel._beating = True
             self.connection_state = KernelConnectionState.SpyderKernelReady
             self.sig_kernel_is_ready.emit()
 

spyder/plugins/ipythonconsole/widgets/status.py

@@ -7,9 +7,13 @@
 """Status bar widgets."""
 
 # Standard library imports
+import functools
 import sys
 import textwrap
 
+# Third-party imports
+from spyder_kernels.comms.frontendcomm import CommError
+
 # Local imports
 from spyder.api.shellconnect.mixins import ShellConnectMixin
 from spyder.api.translations import _
@@ -100,9 +104,11 @@ def update_status(self, gui):
     def add_shellwidget(self, shellwidget):
         """Add shellwidget."""
         shellwidget.sig_config_spyder_kernel.connect(
-            lambda sw=shellwidget: self.config_spyder_kernel(sw)
+            functools.partial(self.config_spyder_kernel, shellwidget)
         )
         shellwidget.kernel_handler.sig_kernel_is_ready.connect(
+            # We can't use functools.partial here because it gives memory leaks
+            # in Python versions older than 3.10
             lambda sw=shellwidget: self.on_kernel_start(sw)
         )
 
@@ -117,8 +123,9 @@ def add_shellwidget(self, shellwidget):
     def config_spyder_kernel(self, shellwidget):
         shellwidget.kernel_handler.kernel_comm.register_call_handler(
             "update_matplotlib_gui",
-            lambda gui, sid=id(shellwidget):
-                self.update_matplotlib_gui(gui, sid)
+            functools.partial(
+                self.update_matplotlib_gui, shellwidget_id=id(shellwidget)
+            )
         )
         shellwidget.set_kernel_configuration("update_gui", True)
 
@@ -133,7 +140,12 @@ def on_kernel_start(self, shellwidget):
         if running_in_ci() and not sys.platform.startswith("linux"):
             mpl_backend = "inline"
         else:
-            mpl_backend = shellwidget.get_matplotlib_backend()
+            # Needed when the comm is not connected.
+            # Fixes spyder-ide/spyder#22194
+            try:
+                mpl_backend = shellwidget.get_matplotlib_backend()
+            except CommError:
+                mpl_backend = None
 
         # Hide widget if Matplotlib is not available or failed to import
         if mpl_backend is None: