Allow interrupt during restart of pending kernels (#898)

jupyter_client/consoleapp.py

@@ -32,12 +32,12 @@
 # Aliases and Flags
 # -----------------------------------------------------------------------------
 
-flags = {}
+flags: dict = {}
 flags.update(base_flags)
 # the flags that are specific to the frontend
 # these must be scrubbed before being passed to the kernel,
 # or it will raise an error on unrecognized flags
-app_flags = {
+app_flags: dict = {
     "existing": (
         {"JupyterConsoleApp": {"existing": "kernel*.json"}},
         "Connect to an existing kernel. If no argument specified, guess most recent",
@@ -61,11 +61,11 @@
 )
 flags.update(app_flags)
 
-aliases = {}
+aliases: dict = {}
 aliases.update(base_aliases)
 
 # also scrub aliases from the frontend
-app_aliases = {
+app_aliases: dict = {
     "ip": "JupyterConsoleApp.ip",
     "transport": "JupyterConsoleApp.transport",
     "hb": "JupyterConsoleApp.hb_port",

jupyter_client/kernelspecapp.py

@@ -301,8 +301,8 @@ class KernelSpecApp(Application):
         }
     )
 
-    aliases: t.Dict[str, object] = {}
-    flags: t.Dict[str, object] = {}
+    aliases: t.Dict[str, object] = {}  # type:ignore[assignment]
+    flags: t.Dict[str, object] = {}  # type:ignore[assignment]
 
     def start(self):
         if self.subapp is None:

jupyter_client/manager.py

@@ -594,6 +594,18 @@ async def _async_interrupt_kernel(self) -> None:
         Unlike ``signal_kernel``, this operation is well supported on all
         platforms.
         """
+        if not self.has_kernel:
+            if self._ready is not None:
+                if isinstance(self._ready, CFuture):
+                    ready = asyncio.ensure_future(self._ready)  # type:ignore
+                else:
+                    ready = self._ready
+                # Wait for a shutdown if one is in progress.
+                if self.shutting_down:
+                    await ready
+                # Wait for a startup.
+                await ready
+
         if self.has_kernel:
             assert self.kernel_spec is not None
             interrupt_mode = self.kernel_spec.interrupt_mode

tests/test_multikernelmanager.py

@@ -311,10 +311,12 @@ async def _run_lifecycle(km, test_kid=None):
         assert kid in km
         assert kid in km.list_kernel_ids()
         assert len(km) == 1, f"{len(km)} != {1}"
-        await km.restart_kernel(kid, now=True)
+        # Ensure we can interrupt during a restart.
+        fut = km.restart_kernel(kid, now=True)
+        await km.interrupt_kernel(kid)
         assert await km.is_alive(kid)
+        await fut
         assert kid in km.list_kernel_ids()
-        await km.interrupt_kernel(kid)
         k = km.get_kernel(kid)
         assert isinstance(k, AsyncKernelManager)
         await km.shutdown_kernel(kid, now=True)