ref: Support outgoing trace propagation in span first (18)

[sentrivana]

Couple things going on in this PR. Bear with me, this is probably the most all over the place span first PR because the outgoing trace propagation changes make mypy complain about things elsewhere in the sdk.

1. Outgoing trace propagation

Support getting trace propagation information from the span with _get_traceparent, _get_baggage, _iter_headers, etc. These mirror the old Span class to make integrating StreamedSpans with the rest of the SDK easier (since they're used throughout), with one difference: they're explicitly private, while the corresponding Span methods were public. Added aliases to them so that we can use the private methods everywhere.

There is definite clean up potential here once we get rid of the old spans and we no longer have to make the streaming span interface work with the existing helper scope methods.

2. Addressing cascading mypy issues

Now that we're officially allowing StreamedSpans to be set on the scope, a LOT of type hints need updating all over the SDK. In many places, I've added explicit guards against functionality that doesn't exist in span first mode. This should prevent folks from using the wrong APIs in the wrong SDK mode (tracing vs. static) as well as make mypy happy.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Autofix Details

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Early return skips _transaction_info source update
  • Replaced the NoOpStreamedSpan early return with a no-op branch so set_transaction_name(..., source=...) always reaches the scope-level _transaction_info["source"] update.

Or push these changes by commenting:

@cursor push 6ca52a0405

Preview (6ca52a0405)

diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -842,7 +842,7 @@
         self._transaction = name
         if self._span:
             if isinstance(self._span, NoOpStreamedSpan):
-                return
+                pass
 
             elif isinstance(self._span, StreamedSpan):
                 self._span._segment.name = name

_{This Bugbot Autofix run was free. To enable autofix for future PRs, go to the Cursor dashboard.}

[cursor]

set_span_errored crashes on NoOpStreamedSpan accessing unset _segment

High Severity

When set_span_errored is called and the current span is a NoOpStreamedSpan, the isinstance(span, StreamedSpan) check passes (since NoOpStreamedSpan inherits from StreamedSpan), but accessing span._segment on the next line raises AttributeError. NoOpStreamedSpan.__init__ never assigns _segment because it doesn't call super().__init__(). This crashes whenever an error occurs while an unsampled or ignored span is active in span streaming mode.

 

[sentry]

Bug: The populate_from_segment function will crash with a TypeError when called on a child span because segment._sample_rand can be None but is formatted as a float.
_{Severity: HIGH}

Suggested Fix

In populate_from_segment, add a check to ensure segment._sample_rand is not None before attempting to format it and add it to the sentry_items dictionary.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: sentry_sdk/tracing_utils.py#L781

Potential issue: The function `populate_from_segment` attempts to format
`segment._sample_rand` as a float. However, for child spans created via
`scope.start_streamed_span`, the `_sample_rand` attribute is not initialized and remains
`None`. This results in a `TypeError` when any function that relies on baggage
information, such as `scope.get_baggage()` or `scope.iter_trace_propagation_headers()`,
is called on a child span. This will cause a runtime crash during normal trace
propagation for outgoing requests involving child spans.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

[cursor]

Duplicate header name constants across traces.py and tracing.py

Low Severity

BAGGAGE_HEADER_NAME and SENTRY_TRACE_HEADER_NAME are now defined identically in both traces.py and tracing.py. These duplicate definitions can drift out of sync and add maintenance burden. One module could import from the other, or they could be extracted to a shared location.