chore(di): fix infinite loop in exception replay (#9317)

The change that added third-party code detection to exception replay
introduced a potential infinite loop. We change the coding to avoid that
scenario.

## Checklist

- [x] Change(s) are motivated and described in the PR description
- [x] Testing strategy is described if automated tests are not included
in the PR
- [x] Risks are described (performance impact, potential for breakage,
maintainability)
- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed or label `changelog/no-changelog` is set
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/))
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
- [x] If this PR changes the public interface, I've notified
`@DataDog/apm-tees`.

## Reviewer Checklist

- [ ] Title is accurate
- [ ] All changes are related to the pull request's stated goal
- [ ] Description motivates each change
- [ ] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- [ ] Testing strategy adequately addresses listed risks
- [ ] Change is maintainable (easy to change, telemetry, documentation)
- [ ] Release note makes sense to a user of the library
- [ ] Author has acknowledged and discussed the performance implications
of this PR as reported in the benchmarks PR comment
- [ ] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

ddtrace/debugging/_exception/auto_instrument.py

@@ -178,34 +178,32 @@ def on_span_finish(self, span: Span) -> None:
                 code = frame.f_code
                 seq_nr = next(seq)
 
-                if not is_user_code(Path(frame.f_code.co_filename)):
-                    continue
-
-                snapshot_id = frame.f_locals.get(SNAPSHOT_KEY, None)
-                if snapshot_id is None:
-                    # We don't have a snapshot for the frame so we create one
-                    snapshot = SpanExceptionSnapshot(
-                        probe=SpanExceptionProbe.build(exc_id, frame),
-                        frame=frame,
-                        thread=current_thread(),
-                        trace_context=span,
-                        exc_id=exc_id,
-                    )
-
-                    # Capture
-                    snapshot.line()
-
-                    # Collect
-                    self.collector.push(snapshot)
-
-                    # Memoize
-                    frame.f_locals[SNAPSHOT_KEY] = snapshot_id = snapshot.uuid
-
-                # Add correlation tags on the span
-                span.set_tag_str(FRAME_SNAPSHOT_ID_TAG % seq_nr, snapshot_id)
-                span.set_tag_str(FRAME_FUNCTION_TAG % seq_nr, code.co_name)
-                span.set_tag_str(FRAME_FILE_TAG % seq_nr, code.co_filename)
-                span.set_tag_str(FRAME_LINE_TAG % seq_nr, str(_tb.tb_lineno))
+                if is_user_code(Path(frame.f_code.co_filename)):
+                    snapshot_id = frame.f_locals.get(SNAPSHOT_KEY, None)
+                    if snapshot_id is None:
+                        # We don't have a snapshot for the frame so we create one
+                        snapshot = SpanExceptionSnapshot(
+                            probe=SpanExceptionProbe.build(exc_id, frame),
+                            frame=frame,
+                            thread=current_thread(),
+                            trace_context=span,
+                            exc_id=exc_id,
+                        )
+
+                        # Capture
+                        snapshot.line()
+
+                        # Collect
+                        self.collector.push(snapshot)
+
+                        # Memoize
+                        frame.f_locals[SNAPSHOT_KEY] = snapshot_id = snapshot.uuid
+
+                    # Add correlation tags on the span
+                    span.set_tag_str(FRAME_SNAPSHOT_ID_TAG % seq_nr, snapshot_id)
+                    span.set_tag_str(FRAME_FUNCTION_TAG % seq_nr, code.co_name)
+                    span.set_tag_str(FRAME_FILE_TAG % seq_nr, code.co_filename)
+                    span.set_tag_str(FRAME_LINE_TAG % seq_nr, str(_tb.tb_lineno))
 
                 # Move up the stack
                 _tb = _tb.tb_next

tests/debugging/exception/test_auto_instrument.py

@@ -4,6 +4,7 @@
 
 import ddtrace
 import ddtrace.debugging._exception.auto_instrument as auto_instrument
+from ddtrace.internal.packages import _third_party_packages
 from ddtrace.internal.rate_limiter import BudgetRateLimiterWithJitter as RateLimiter
 from tests.debugging.mocking import exception_debugging
 from tests.utils import TracerTestCase
@@ -24,8 +25,10 @@ def setUp(self):
         super(ExceptionDebuggingTestCase, self).setUp()
         self.backup_tracer = ddtrace.tracer
         ddtrace.tracer = self.tracer
+        _third_party_packages().remove("ddtrace")
 
     def tearDown(self):
+        _third_party_packages().add("ddtrace")
         ddtrace.tracer = self.backup_tracer
         super(ExceptionDebuggingTestCase, self).tearDown()