From 5ca25081d6a6dc53c6ee05b001b0aad232d055e0 Mon Sep 17 00:00:00 2001
From: Patric Stout <truebrain@openttd.org>
Date: Fri, 13 Nov 2020 11:31:34 +0100
Subject: [PATCH] Fix #75: escalate exceptions from tasks to main thread (#78)

This means that an unexpected exception will terminate the
application completely, instead of hiding away a bit.
---
 truewiki/metadata.py       | 14 +++++++++++++-
 truewiki/storage/git.py    | 25 ++++++++++++++++++++++---
 truewiki/storage/github.py |  7 ++-----
 3 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/truewiki/metadata.py b/truewiki/metadata.py
index 71fbc4e..47fe446 100644
--- a/truewiki/metadata.py
+++ b/truewiki/metadata.py
@@ -214,9 +214,21 @@ async def _scan_folder(folder, notified=None):
     return pages_seen
 
 
+def check_for_exception(task):
+    exception = task.exception()
+    if exception:
+        log.exception("Exception in metadata_queue()", exc_info=exception)
+
+        # We terminate the application, as this is a real problem from which we
+        # cannot recover cleanly. This is needed, as we run in a co-routine, and
+        # there is no other way to notify the main thread we are terminating.
+        sys.exit(1)
+
+
 def load_metadata():
     loop = asyncio.get_event_loop()
-    loop.create_task(metadata_queue("load_metadata", None))
+    task = loop.create_task(metadata_queue("load_metadata", None))
+    task.add_done_callback(check_for_exception)
 
 
 def page_changed(pages):
diff --git a/truewiki/storage/git.py b/truewiki/storage/git.py
index 29ffaaa..b77c761 100644
--- a/truewiki/storage/git.py
+++ b/truewiki/storage/git.py
@@ -1,13 +1,17 @@
 import asyncio
 import click
 import git
+import logging
 import multiprocessing
+import sys
 
 from concurrent import futures
 from openttd_helpers import click_helper
 
 from . import local
 
+log = logging.getLogger(__name__)
+
 GIT_USERNAME = None
 GIT_EMAIL = None
 
@@ -46,6 +50,17 @@ def commit(self, git_author, commit_message, files_added, files_changed, files_r
         return True
 
 
+def check_for_exception(task):
+    exception = task.exception()
+    if exception and not isinstance(exception, asyncio.exceptions.CancelledError):
+        log.exception("Exception in git command", exc_info=exception)
+
+        # We terminate the application, as this is a real problem from which we
+        # cannot recover cleanly. This is needed, as we run in a co-routine, and
+        # there is no other way to notify the main thread we are terminating.
+        sys.exit(1)
+
+
 class Storage(local.Storage):
     out_of_process_class = OutOfProcessStorage
 
@@ -80,7 +95,7 @@ def _init_repository(self):
 
         return _git
 
-    async def _run_out_of_process(self, folder, ssh_command, callback, func, *args):
+    async def _run_out_of_process_async(self, folder, ssh_command, callback, func, *args):
         await GIT_BUSY.wait()
         GIT_BUSY.clear()
 
@@ -108,6 +123,11 @@ async def _run_out_of_process(self, folder, ssh_command, callback, func, *args):
         if callback:
             callback()
 
+    def _run_out_of_process(self, callback, func, *args):
+        loop = asyncio.get_event_loop()
+        task = loop.create_task(self._run_out_of_process_async(self._folder, self._ssh_command, callback, func, *args))
+        task.add_done_callback(check_for_exception)
+
     def commit(self, user, commit_message):
         args = (
             user.get_git_author(),
@@ -120,8 +140,7 @@ def commit(self, user, commit_message):
         self._files_changed.clear()
         self._files_removed.clear()
 
-        loop = asyncio.get_event_loop()
-        loop.create_task(self._run_out_of_process(self._folder, self._ssh_command, self.commit_done, "commit", *args))
+        self._run_out_of_process(self.commit_done, "commit", *args)
 
     def commit_done(self):
         pass
diff --git a/truewiki/storage/github.py b/truewiki/storage/github.py
index 0c626ce..6597be4 100644
--- a/truewiki/storage/github.py
+++ b/truewiki/storage/github.py
@@ -1,4 +1,3 @@
-import asyncio
 import base64
 import click
 import git
@@ -104,15 +103,13 @@ def prepare(self):
         return _git
 
     def reload(self):
-        loop = asyncio.get_event_loop()
-        loop.create_task(self._run_out_of_process(self._folder, self._ssh_command, self._reload_done, "fetch_latest"))
+        self._run_out_of_process(self._reload_done, "fetch_latest")
 
     def _reload_done(self):
         super().reload()
 
     def commit_done(self):
-        loop = asyncio.get_event_loop()
-        loop.create_task(self._run_out_of_process(self._folder, self._ssh_command, None, "push"))
+        self._run_out_of_process(None, "push")
 
     def get_history_url(self, page):
         page = urllib.parse.quote(page)