[#23] chained exceptions (and improved coverage)

memoize/wrapper.py

@@ -78,7 +78,7 @@ async def refresh(actual_entry: Optional[CacheEntry], key: CacheKey,
             logger.debug('As entry expired, waiting for results of concurrent refresh %s', key)
             entry = await update_statuses.await_updated(key)
             if isinstance(entry, Exception):
-                raise CachedMethodFailedException('Concurrent refresh failed to complete', entry)
+                raise CachedMethodFailedException('Concurrent refresh failed to complete') from entry
             return entry
         elif actual_entry is not None and update_statuses.is_being_updated(key):
             logger.debug('As update point reached but concurrent update already in progress, '
@@ -104,11 +104,11 @@ async def refresh(actual_entry: Optional[CacheEntry], key: CacheKey,
             except (asyncio.TimeoutError, _timeout_error_type()) as e:
                 logger.debug('Timeout for %s: %s', key, e)
                 update_statuses.mark_update_aborted(key, e)
-                raise CachedMethodFailedException('Refresh timed out', e)
+                raise CachedMethodFailedException('Refresh timed out') from e
             except Exception as e:
                 logger.debug('Error while refreshing cache for %s: %s', key, e)
                 update_statuses.mark_update_aborted(key, e)
-                raise CachedMethodFailedException('Refresh failed to complete', e)
+                raise CachedMethodFailedException('Refresh failed to complete') from e
 
     @functools.wraps(method)
     async def wrapper(*args, **kwargs):

tests/asynciotests/test_showcase.py

@@ -94,5 +94,5 @@ async def get_value_or_throw(arg, kwarg=None):
         self.assertEqual('ok #2', res4)  # value from cache - still relevant
         self.assertEqual('ok #2', res5)  # stale from cache - refresh in background
         self.assertEqual('ok #2', res6)  # stale from cache - should be updated but method throws
-        expected = CachedMethodFailedException('Refresh failed to complete', ValueError('throws #4', ))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(str(context.exception), str(CachedMethodFailedException('Refresh failed to complete')))
+        self.assertEqual(str(context.exception.__cause__), str(ValueError("throws #4")))

tests/asynciotests/test_wrapper_manually_applied_on_asyncio.py

@@ -1,3 +1,4 @@
+from memoize.coerced import _timeout_error_type
 from tests.py310workaround import fix_python_3_10_compatibility
 
 fix_python_3_10_compatibility()
@@ -274,8 +275,8 @@ async def get_value(arg, kwarg=None):
             await get_value_cached('test1', kwarg='args1')
 
         # then
-        expected = CachedMethodFailedException('Refresh failed to complete', ValueError('Get lost', ))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(str(context.exception), str(CachedMethodFailedException('Refresh failed to complete')))
+        self.assertEqual(str(context.exception.__cause__), str(ValueError("Get lost")))
 
     @gen_test
     async def test_should_throw_exception_on_refresh_timeout(self):
@@ -295,8 +296,8 @@ async def get_value(arg, kwarg=None):
             await get_value_cached('test1', kwarg='args1')
 
         # then
-        expected = CachedMethodFailedException('Refresh timed out', TimeoutError('Timeout'))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(context.exception.__cause__.__class__, _timeout_error_type())
 
     @staticmethod
     async def _call_thrice(call):

tests/asynciotests/test_wrapper_on_asyncio.py

@@ -1,3 +1,4 @@
+from memoize.coerced import _timeout_error_type
 from tests.py310workaround import fix_python_3_10_compatibility
 
 fix_python_3_10_compatibility()
@@ -177,13 +178,51 @@ async def get_value(arg, kwarg=None):
         # then
         with self.assertRaises(Exception) as context:
             await res1
-            self.assertEqual(context.exception, ValueError('stub0'))
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(str(context.exception.__cause__), str(ValueError('stub0')))
+
         with self.assertRaises(Exception) as context:
             await res2
-            self.assertEqual(context.exception, ValueError('stub0'))
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(str(context.exception.__cause__), str(ValueError('stub0')))
+
+        with self.assertRaises(Exception) as context:
+            await res3
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(str(context.exception.__cause__), str(ValueError('stub0')))
+
+    @gen_test
+    async def test_should_return_timeout_for_all_concurrent_callers(self):
+        # given
+        value = 0
+
+        @memoize(configuration=DefaultInMemoryCacheConfiguration(method_timeout=timedelta(milliseconds=1)))
+        async def get_value(arg, kwarg=None):
+            await _ensure_asyncio_background_tasks_finished()
+            time.sleep(.200)
+            await _ensure_asyncio_background_tasks_finished()
+            return value
+
+        # when
+        res1 = get_value('test', kwarg='args1')
+        res2 = get_value('test', kwarg='args1')
+        res3 = get_value('test', kwarg='args1')
+
+        # then
+        with self.assertRaises(Exception) as context:
+            await res1
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(context.exception.__cause__.__class__, _timeout_error_type())
+
         with self.assertRaises(Exception) as context:
             await res2
-            self.assertEqual(context.exception, ValueError('stub0'))
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(context.exception.__cause__.__class__, _timeout_error_type())
+
+        with self.assertRaises(Exception) as context:
+            await res3
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(context.exception.__cause__.__class__, _timeout_error_type())
 
     @gen_test
     async def test_should_return_same_value_on_constant_key_function(self):
@@ -278,8 +317,8 @@ async def get_value(arg, kwarg=None):
             await get_value('test1', kwarg='args1')
 
         # then
-        expected = CachedMethodFailedException('Refresh failed to complete', ValueError('Get lost', ))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(str(context.exception), str(CachedMethodFailedException('Refresh failed to complete')))
+        self.assertEqual(str(context.exception.__cause__), str(ValueError("Get lost")))
 
     @gen_test
     async def test_should_throw_exception_on_refresh_timeout(self):
@@ -297,8 +336,9 @@ async def get_value(arg, kwarg=None):
             await get_value('test1', kwarg='args1')
 
         # then
-        expected = CachedMethodFailedException('Refresh timed out', TimeoutError('Timeout'))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(context.exception.__cause__.__class__, _timeout_error_type())
+
 
     @staticmethod
     async def _call_thrice(call):

tests/tornadotests/test_wrapper.py

@@ -1,3 +1,4 @@
+from memoize.coerced import _timeout_error_type
 from tests.py310workaround import fix_python_3_10_compatibility
 
 fix_python_3_10_compatibility()
@@ -265,8 +266,8 @@ def get_value(arg, kwarg=None):
             yield get_value('test1', kwarg='args1')
 
         # then
-        expected = CachedMethodFailedException('Refresh failed to complete', ValueError('Get lost', ))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(str(context.exception), str(CachedMethodFailedException('Refresh failed to complete')))
+        self.assertEqual(str(context.exception.__cause__), str(ValueError("Get lost")))
 
     @gen_test
     def test_should_throw_exception_on_refresh_timeout(self):
@@ -285,5 +286,6 @@ def get_value(arg, kwarg=None):
             yield get_value('test1', kwarg='args1')
 
         # then
-        expected = CachedMethodFailedException('Refresh timed out', TimeoutError('Timeout'))
-        self.assertEqual(str(expected), str(context.exception))  # ToDo: consider better comparision
+        self.assertEqual(context.exception.__class__, CachedMethodFailedException)
+        self.assertEqual(context.exception.__cause__.__class__, _timeout_error_type())
+