fix(traces): walk every hook attribute again, and record the new callback alias

Skipping values the hook left as the same object let a container grown
in place ship past max_attribute_value_length. The public API snapshot
gains BeforeSpanSendCallback.

Author: turnipdabeets

posthog/test/tracing/test_limits.py

@@ -186,20 +186,12 @@ def test_stops_walking_a_mapping_at_the_encoders_item_cap(self):
 
 
 class TestApplySpanLimits:
-    def test_walks_only_values_the_hook_changed(self):
-        untouched = ["already", "bounded"]
-        record = SpanRecord(
-            "t", "s", "n", 1, 2, attributes={"same": untouched, "new": "x" * 9}
-        )
-        with mock.patch.object(
-            limits_module, "truncate_attribute_value", wraps=truncate_attribute_value
-        ) as walk:
-            apply_span_limits(
-                record, frozenset(), 128, 128, 128, 8, (), {"same": untouched}
-            )
-        assert walk.call_args_list == [mock.call("x" * 9, 8)]
-        assert record.attributes["same"] is untouched
-        assert record.attributes["new"] == "x" * 8
+    def test_rebounds_a_container_the_hook_grew_in_place(self):
+        grown = ["x" * 3]
+        record = SpanRecord("t", "s", "n", 1, 2, attributes={"k": grown})
+        grown.append("y" * 20)
+        apply_span_limits(record, frozenset(), 128, 128, 128, 8)
+        assert record.attributes["k"] == ["xxx", "y" * 8]
 
     def test_an_empty_key_spends_no_slot(self):
         record = SpanRecord("t", "s", "n", 1, 2, attributes={"": 1, "a": 2, "b": 3})

posthog/tracing/_before_span_send.py

@@ -74,7 +74,6 @@ def run_before_span_send(
             MAX_ATTRIBUTES_PER_EVENT,
             config.max_attribute_value_length,
             keys_before_hook,
-            record.attributes,
         )
         return rebuilt
     except Exception:

posthog/tracing/_limits.py

@@ -163,11 +163,12 @@ def apply_span_limits(
     max_attributes_per_event: int,
     max_length: int,
     keys_before_hook: Sequence[str] = (),
-    bounded_before_hook: Mapping[str, Any] = {},
 ) -> None:
     """Re-apply the per-span caps after a ``before_span_send`` hook, which
     bypasses the span's own writer. Counts add to what the span already dropped.
-    A value still the object the span bounded at write time is not walked again."""
+
+    Every container is walked again: the hook holds the same nested objects
+    the span stored, so one it grew in place has the same identity."""
     attributes: Dict[str, Any] = {}
     kept = 0
     dropped_attributes = 0
@@ -180,10 +181,7 @@ def apply_span_limits(
                 dropped_attributes += 1
                 continue
             kept += 1
-        if bounded_before_hook.get(key) is value:
-            attributes[key] = value
-        else:
-            attributes[key] = truncate_attribute_value(value, max_length)
+        attributes[key] = truncate_attribute_value(value, max_length)
     record.attributes = attributes
     if dropped_attributes:
         record.dropped_attributes_count = (

references/public_api_snapshot.txt

@@ -888,6 +888,7 @@ attribute posthog.send = True
 attribute posthog.super_properties = None
 attribute posthog.sync_mode = False
 attribute posthog.types.BeforeSendCallback = Callable[[dict[str, Any]], Optional[dict[str, Any]]]
+attribute posthog.types.BeforeSpanSendCallback = Callable[[dict[str, Any]], Optional[dict[str, Any]]]
 attribute posthog.types.FeatureFlag.enabled: bool
 attribute posthog.types.FeatureFlag.key: str
 attribute posthog.types.FeatureFlag.metadata: Union[FlagMetadata, LegacyFlagMetadata]