fix: collect exceptions on task errors

When async tasks fail, all exceptions need to be collected to not get
subsequent exceptions about invalid future states. This is achieved by
gathering the task results, instead of just waiting for them. By
gathering the results, also user-requested cancellation (e.g. via
ctrl-c) works without throwing tons of additional exceptions.
Since ac437308 we more likely run into that case, which unvealed the bug.

By properly handling the exception, a TaskResultError is returned
instead of the underlying CommandExecError. This change is reflected in
the corresponding unit test.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/kas.py

@@ -98,7 +98,14 @@ def _atexit_handler():
         loop = asyncio.get_event_loop()
         pending = asyncio.Task.all_tasks(loop)
     if not loop.is_closed():
+        # this code path is observed on older python versions (e.g. 3.6).
+        # In case the loop is not yet closed, tasks still might throw
+        # exceptions, but we are not interested in these as they are
+        # likely due to the cancellation. By that, we simply drop them.
+        try:
             loop.run_until_complete(asyncio.gather(*pending))
+        except KasUserError:
+            pass
         loop.close()
 
 

kas/libkas.py

@@ -197,11 +197,10 @@ def repos_fetch(repos):
         tasks.append(asyncio.ensure_future(repo.fetch_async()))
 
     loop = asyncio.get_event_loop()
-    loop.run_until_complete(asyncio.wait(tasks))
-
-    for task in tasks:
-        if task.result():
-            raise TaskExecError('fetch repos', task.result())
+    try:
+        loop.run_until_complete(asyncio.gather(*tasks))
+    except CommandExecError as e:
+        raise TaskExecError('fetch repos', e.ret_code)
 
 
 def repos_apply_patches(repos):
@@ -216,11 +215,10 @@ def repos_apply_patches(repos):
         tasks.append(asyncio.ensure_future(repo.apply_patches_async()))
 
     loop = asyncio.get_event_loop()
-    loop.run_until_complete(asyncio.wait(tasks))
-
-    for task in tasks:
-        if task.result():
-            raise TaskExecError('apply patches', task.result())
+    try:
+        loop.run_until_complete(asyncio.gather(*tasks))
+    except CommandExecError as e:
+        raise TaskExecError('apply patches', e.ret_code)
 
 
 def get_build_environ(build_system):

tests/test_commands.py

@@ -28,7 +28,7 @@ import json
 import yaml
 import pytest
 from kas import kas
-from kas.kasusererror import CommandExecError
+from kas.libkas import TaskExecError
 
 
 def test_for_all_repos(changedir, tmpdir):
@@ -67,7 +67,7 @@ def test_invalid_checkout(changedir, tmpdir, capsys):
     tdir = str(tmpdir / 'test_commands')
     shutil.copytree('tests/test_commands', tdir)
     os.chdir(tdir)
-    with pytest.raises(CommandExecError):
+    with pytest.raises(TaskExecError):
         kas.kas(['checkout', 'test-invalid.yml'])