PR: Fix kernel restarts after a crash for external interpreters

spyder/plugins/ipythonconsole/tests/test_ipythonconsole.py

@@ -1608,35 +1608,55 @@ def test_conda_env_activation(ipyconsole, qtbot):
 
 
 @flaky(max_runs=3)
+@pytest.mark.parametrize("external_interpreter", [True, False])
 @pytest.mark.skipif(os.name == 'nt', reason="no SIGTERM on Windows")
-def test_kernel_kill(ipyconsole, qtbot):
+def test_kernel_kill(ipyconsole, qtbot, external_interpreter):
     """
     Test that the kernel correctly restarts after a kill.
     """
+    if external_interpreter:
+        if bool(os.environ.get('CI')):
+            CONF.set('main_interpreter', 'default', False)
+            CONF.set('main_interpreter', 'executable', get_conda_test_env())
+            ipyconsole.create_new_client()
+        else:
+            # We can't check this locally
+            return
+
     shell = ipyconsole.get_current_shellwidget()
     qtbot.waitUntil(lambda: shell._prompt_html is not None,
                     timeout=SHELL_TIMEOUT)
     # Wait for the restarter to start
     qtbot.wait(3000)
     crash_string = 'import os, signal; os.kill(os.getpid(), signal.SIGTERM)'
+
     # Check only one comm is open
     old_open_comms = list(shell.spyder_kernel_comm._comms.keys())
     assert len(old_open_comms) == 1
     with qtbot.waitSignal(shell.sig_prompt_ready, timeout=30000):
         shell.execute(crash_string)
     assert crash_string in shell._control.toPlainText()
-    assert "Restarting kernel..." in shell._control.toPlainText()
+
+    if not external_interpreter:
+        assert "Restarting kernel..." in shell._control.toPlainText()
+
     # Check a new comm replaced the old one
     new_open_comms = list(shell.spyder_kernel_comm._comms.keys())
     assert len(new_open_comms) == 1
     assert old_open_comms[0] != new_open_comms[0]
+
     # Wait until the comm replies
     qtbot.waitUntil(
         lambda: shell.spyder_kernel_comm._comms[new_open_comms[0]][
             'status'] == 'ready')
     assert shell.spyder_kernel_comm._comms[new_open_comms[0]][
         'status'] == 'ready'
 
+    # Reset interpreter
+    if external_interpreter:
+        CONF.set('main_interpreter', 'default', True)
+        CONF.set('main_interpreter', 'executable', '')
+
 
 @flaky(max_runs=3)
 def test_wrong_std_module(ipyconsole, qtbot):

spyder/plugins/ipythonconsole/widgets/client.py

@@ -311,9 +311,6 @@ def configure_shellwidget(self, give_focus=True):
         # To sync with working directory toolbar
         self.shellwidget.executed.connect(self.shellwidget.update_cwd)
 
-        # To apply style
-        self.set_color_scheme(self.shellwidget.syntax_style, reset=False)
-
     def add_to_history(self, command):
         """Add command to history"""
         if self.shellwidget.is_debugging():
@@ -340,10 +337,19 @@ def _when_prompt_is_ready(self):
         # To show if special console is valid
         self._check_special_console_error()
 
+        # To apply style at kernel startup or kernel crashes
+        self.set_color_scheme(self.shellwidget.syntax_style, reset=False)
+
+        # Don't call this method for any new prompt
         self.shellwidget.sig_prompt_ready.disconnect(
             self._when_prompt_is_ready)
-        self.shellwidget.sig_remote_execute.disconnect(
-            self._when_prompt_is_ready)
+
+        # This signal is not connected in a kernel crash
+        try:
+            self.shellwidget.sig_remote_execute.disconnect(
+                self._when_prompt_is_ready)
+        except TypeError:
+            pass
 
     def enable_stop_button(self):
         self.stop_button.setEnabled(True)
@@ -641,8 +647,13 @@ def _finalise_restart(self, reset=False):
         """Finishes the restarting of the kernel."""
         sw = self.shellwidget
 
-        if self._abort_kernel_restart():
+        if self.get_stderr_contents():
             sw.spyder_kernel_comm.close()
+            self.stop_button.setDisabled(True)
+
+            # This covers the case of kernel crashes that generate stderr
+            # content, but still can recover and start a new kernel.
+            sw.sig_prompt_ready.connect(self._when_prompt_is_ready)
             return
 
         if self.restart_thread and self.restart_thread.error is not None: