fix(sdk_crashes): KeyError for multiple exceptions (#97829)

Only keep the last exception when a crash has multiple ones. The SDK
crash detection only detects crashes based on the last exception.
Keeping multiple exceptions and stripping data would be the ideal
solution, but that requires more changes.
We're going to follow up to make this work with
#97830.

Author: philipphofmann

src/sentry/utils/sdk_crashes/event_stripper.py

@@ -114,16 +114,32 @@ def strip_event_data(
     and the method only keeps SDK frames and system library frames.
     """
 
-    frames = get_path(event_data, "exception", "values", -1, "stacktrace", "frames")
-    if not frames:
+    last_exception = get_path(
+        event_data,
+        "exception",
+        "values",
+        -1,
+    )
+    if not last_exception:
         return {}
 
+    # The SDK crash detector only detects crashes based on the last exception value.
+    # Therefore, if the last exception doesn't contain a stacktrace something is off and
+    # we can drop the whole event.
+    last_exception_frames = get_path(last_exception, "stacktrace", "frames")
+    if not last_exception_frames:
+        return {}
+
+    event_data_copy = dict(event_data)
+
     # We strip the frames first because applying the allowlist removes fields that are needed
     # for deciding wether to keep a frame or not.
-    stripped_frames = _strip_frames(frames, sdk_crash_detector)
+    stripped_frames = _strip_frames(last_exception_frames, sdk_crash_detector)
+    last_exception["stacktrace"]["frames"] = stripped_frames
 
-    event_data_copy = dict(event_data)
-    event_data_copy["exception"]["values"][0]["stacktrace"]["frames"] = stripped_frames
+    # We only keep the last exception. We need to adopt the allowlist and stripping event data logic
+    # to support multiple exceptions.
+    event_data_copy["exception"]["values"] = [last_exception]
 
     stripped_event_data = _strip_event_data_with_allowlist(event_data_copy, EVENT_DATA_ALLOWLIST)
 

tests/sentry/utils/sdk_crashes/test_event_stripper.py

@@ -452,3 +452,77 @@ def test_strip_event_without_frames_returns_empty_dict(store_and_strip_event) ->
     stripped_event_data = store_and_strip_event(data=event_data)
 
     assert stripped_event_data == {}
+
+
+@django_db_all
+@pytest.mark.snuba
+def test_strip_event_with_multiple_exceptions_only_keep_last_one(store_and_strip_event) -> None:
+    event_data = get_crash_event()
+
+    exception_values = list(get_path(event_data, "exception", "values"))
+
+    crash_exception = dict(exception_values[0])
+    set_path(crash_exception, "type", value="SIGPIPE")
+    set_path(crash_exception, "value", value="Broken pipe")
+
+    exception_values.append(crash_exception)
+
+    set_path(event_data, "exception", "values", value=exception_values)
+
+    stripped_event_data = store_and_strip_event(data=event_data)
+
+    assert len(get_path(stripped_event_data, "exception", "values")) == 1
+
+    exception = get_path(stripped_event_data, "exception", "values", 0)
+    assert exception["type"] == "SIGPIPE"
+    assert "value" not in exception
+
+
+@django_db_all
+@pytest.mark.snuba
+def test_strip_event_with_multiple_exceptions_last_without_frames_discard_event(
+    store_and_strip_event,
+) -> None:
+    event_data = get_crash_event()
+
+    exception_values = list(get_path(event_data, "exception", "values"))
+
+    crash_exception = dict(exception_values[0])
+    set_path(crash_exception, "type", value="SIGPIPE")
+    set_path(crash_exception, "value", value="Broken pipe")
+    set_path(crash_exception, "stacktrace", value=None)
+    exception_values.append(crash_exception)
+
+    set_path(event_data, "exception", "values", value=exception_values)
+
+    stripped_event_data = store_and_strip_event(data=event_data)
+
+    assert stripped_event_data == {}
+
+
+@django_db_all
+@pytest.mark.snuba
+def test_strip_event_with_multiple_exceptions_first_without_frames_keeps_last_exception(
+    store_and_strip_event,
+) -> None:
+    event_data = get_crash_event()
+
+    exception_values = list(get_path(event_data, "exception", "values"))
+
+    crash_exception = dict(exception_values[0])
+    set_path(crash_exception, "type", value="SIGPIPE")
+    set_path(crash_exception, "value", value="Broken pipe")
+    exception_values.append(crash_exception)
+
+    # Remove the stacktrace from the first exception.
+    exception_values[0]["stacktrace"] = None
+
+    set_path(event_data, "exception", "values", value=exception_values)
+
+    stripped_event_data = store_and_strip_event(data=event_data)
+
+    assert len(get_path(stripped_event_data, "exception", "values")) == 1
+
+    exception = get_path(stripped_event_data, "exception", "values", 0)
+    assert exception["type"] == "SIGPIPE"
+    assert "value" not in exception