make SingleInstanceTask.start_sync set self.task synchronously

subiquity/controllers/refresh.py

@@ -13,6 +13,7 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import asyncio
 import enum
 import logging
 import os
@@ -57,22 +58,23 @@ class RefreshController(BaseController):
 
     def start(self):
         self.configure_task = schedule_task(self.configure_snapd())
-        self.check_task_starter = SingleInstanceTask(
+        self.check_task = SingleInstanceTask(
             self.check_for_update, propagate_errors=False)
-        self.check_task_starter.start_sync()
+        self.check_task.start_sync()
 
     @property
     def check_state(self):
-        task = self.check_task_starter.task
-        if task is None:
-            return CheckState.UNKNOWN
+        task = self.check_task.task
         if not task.done():
             return CheckState.UNKNOWN
+        if task.cancelled():
+            return CheckState.UNKNOWN
         if task.exception():
             return CheckState.UNAVAILABLE
         return task.result()
 
     async def configure_snapd(self):
+        log.debug("configure_snapd")
         try:
             r = await self.app.snapd.get(
                 'v2/snaps/{snap_name}'.format(snap_name=self.snap_name))
@@ -130,10 +132,10 @@ class RefreshController(BaseController):
 
     def snapd_network_changed(self):
         if self.check_state == CheckState.UNKNOWN:
-            self.check_task_starter.start_sync()
+            self.check_task.start_sync()
 
     async def check_for_update(self):
-        await self.configure_task
+        await asyncio.shield(self.configure_task)
         # If we restarted into this version, don't check for a new version.
         if self.app.updated:
             return CheckState.UNAVAILABLE

subiquitycore/async_helpers.py

@@ -14,6 +14,10 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import asyncio
+import logging
+
+
+log = logging.getLogger("subiquitycore.async_helpers")
 
 
 def _done(fut):
@@ -47,16 +51,24 @@ class SingleInstanceTask:
         self.propagate_errors = propagate_errors
         self.task = None
 
-    async def start(self, *args, **kw):
-        if self.task is not None:
-            self.task.cancel()
+    async def _start(self, old):
+        if old is not None:
+            old.cancel()
             try:
-                await self.task
+                await old
             except BaseException:
                 pass
-        self.task = schedule_task(
-            self.func(*args, **kw), self.propagate_errors)
+        schedule_task(self.task, self.propagate_errors)
+
+    async def start(self, *args, **kw):
+        await self.start_sync(*args, **kw)
         return self.task
 
     def start_sync(self, *args, **kw):
-        return schedule_task(self.start(*args, **kw))
+        old = self.task
+        coro = self.func(*args, **kw)
+        if asyncio.iscoroutine(coro):
+            self.task = asyncio.Task(coro)
+        else:
+            self.task = coro
+        return schedule_task(self._start(old))