fix(tracing): span pointer __repr__ (#14539)

## What's the issue
In the _SpanPointer.__repr__ method, it's trying to access
self.direction and self.hash, but these attributes don't exist on the
object. The _SpanPointer class:
  1. It inherits from SpanLink
2. The direction and hash information are stored in the attributes
dictionary as "ptr.dir" and "ptr.hash"
Therefore the fix.

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, 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)

Author: joeyzhao2018

ddtrace/_trace/_span_pointer.py

@@ -64,7 +64,8 @@ def __post_init__(self):
     def __repr__(self):
         return (
             f"SpanPointer(trace_id={self.trace_id}, span_id={self.span_id}, kind={self.kind}, "
-            f"direction={self.direction}, hash={self.hash}, attributes={self.attributes})"
+            f"direction={self.attributes.get('ptr.dir')}, hash={self.attributes.get('ptr.hash')}, "
+            f"attributes={self.attributes})"
         )
 
 

releasenotes/notes/fix-spanpointer-repr-565ebb8e6679ebde.yaml

@@ -0,0 +1,3 @@
+fixes:
+  - |
+    tracing: Fixes a bug where calling __repr__ on SpanPointer objected raised an AttributeError. This caused aws_lambdas to crash when debug logging was enabled.

tests/tracer/test_span.py

@@ -872,6 +872,7 @@ def test_span_pprint():
     root.set_metric("m", 1.0)
     root._add_event("message", {"importance": 10}, 16789898242)
     root.set_link(trace_id=99, span_id=10, attributes={"link.name": "s1_to_s2", "link.kind": "scheduled_by"})
+    root._add_span_pointer("test_kind", _SpanPointerDirection.DOWNSTREAM, "test_hash_123", {"extra": "attr"})
 
     root.finish()
     actual = root._pprint()
@@ -884,9 +885,11 @@ def test_span_pprint():
     assert "metrics={'m': 1.0}" in actual
     assert "events=[SpanEvent(name='message', time=16789898242, attributes={'importance': 10})]" in actual
     assert (
-        "[SpanLink(trace_id=99, span_id=10, attributes={'link.name': 's1_to_s2', 'link.kind': 'scheduled_by'}, "
-        "tracestate=None, flags=None, dropped_attributes=0)]"
+        "SpanLink(trace_id=99, span_id=10, attributes={'link.name': 's1_to_s2', 'link.kind': 'scheduled_by'}, "
+        "tracestate=None, flags=None, dropped_attributes=0)"
     ) in actual
+    assert "SpanPointer(trace_id=0, span_id=0, kind=span-pointer" in actual
+    assert "direction=d, hash=test_hash_123" in actual
     assert (
         f"context=Context(trace_id={root.trace_id}, span_id={root.span_id}, _meta={{}}, "
         "_metrics={}, _span_links=[], _baggage={}, _is_remote=False)"