add tests for Task reentrancy and call_sync

Author: kristjanvalur

tests/test_qeventloop.py

@@ -791,22 +791,73 @@ async def mycoro():
     loop.run_until_complete(mycoro())
     assert not loop.is_running()
 
+def test_task_recursion_fails(loop, application):
+    """Re-entering the event loop from a Task will fail if there is another
+    runnable task."""
+    async_called = False
+    main_called = False
+    
+    async def async_job():
+        nonlocal async_called
+        async_called = True
 
-def test_call_sync(loop):
-    """Verify that call_sync works as expected."""
-    called = False
+    def sync_callback():
+        asyncio.create_task(async_job())
+        assert not async_called
+        application.processEvents()
+        assert not async_called
+        return 1
+
+    async def main():
+        nonlocal main_called
+        res = sync_callback()
+        assert res == 1
+        main_called = True
+
+    exceptions= []
+    loop.set_exception_handler(lambda loop, context: exceptions.append(context))
+
+    loop.run_until_complete(main())
+    assert main_called, "The main function should have been called"
+    
+    # We will now have an error in there, because the task 'async_job' could not 
+    # be entered, because the task 'main' was still being executed by the event loop.
+    assert len(exceptions) == 1
+    assert isinstance(exceptions[0]["exception"], RuntimeError)
+
+
+def test_call_sync(loop, application):
+    """Re-entering the event loop from a Task will fail if there is another
+    runnable task."""
+    async_called = False
+    main_called = False
+    
+    async def async_job():
+        nonlocal async_called
+        async_called = True
 
     def sync_callback():
-        nonlocal called
-        called = True
+        asyncio.create_task(async_job())
+        assert not async_called
+        application.processEvents()
+        assert async_called
         return 1
 
     async def main():
+        nonlocal main_called
         res = await qasync.call_sync(sync_callback)
         assert res == 1
-        
+        main_called = True
+
+    exceptions= []
+    loop.set_exception_handler(lambda loop, context: exceptions.append(context))
+
     loop.run_until_complete(main())
-    assert called, "The sync callback should have been called"
+    assert main_called, "The main function should have been called"
+    
+    # We will now have an error in there, because the task 'async_job' could not 
+    # be entered, because the task 'main' was still being executed by the event loop.
+    assert len(exceptions) == 0
 
 
 def test_slow_callback_duration_logging(loop, caplog):