fix(sdk): add input sanitization for LangfuseObservationWrapper metadata

langfuse/_client/span.py

@@ -121,6 +121,8 @@ def __init__(
             cost_details: Cost information for the model call
             prompt: Associated prompt template from Langfuse prompt management
         """
+        if isinstance(metadata, dict):
+            metadata = {k: v for k, v in metadata.items() if v is not None and v != ""}
         self._otel_span = otel_span
         self._otel_span.set_attribute(
             LangfuseOtelSpanAttributes.OBSERVATION_TYPE, as_type
@@ -676,6 +678,9 @@ def update(
         if not self._otel_span.is_recording():
             return self
 
+        if isinstance(metadata, dict):
+            metadata = {k: v for k, v in metadata.items() if v is not None and v != ""}
+
         processed_input = self._process_media_and_apply_mask(
             data=input, field="input", span=self._otel_span
         )

tests/unit/test_span_sanitization.py

@@ -0,0 +1,41 @@
+from unittest.mock import MagicMock, patch
+
+from opentelemetry import trace as otel_trace_api
+
+from langfuse._client.span import LangfuseObservationWrapper
+
+
+@patch("langfuse._client.span.LangfuseObservationWrapper._process_media_and_apply_mask")
+def test_langfuse_observation_wrapper_metadata_sanitization(mock_process):
+    mock_otel_span = MagicMock(spec=otel_trace_api.Span)
+    mock_otel_span.is_recording.return_value = True
+
+    mock_client = MagicMock()
+
+    # Input with empty string value and None value
+    bad_metadata = {"valid_key": "value", "bad_empty": "", "bad_none": None}
+
+    wrapper = LangfuseObservationWrapper(
+        otel_span=mock_otel_span,
+        langfuse_client=mock_client,
+        as_type="span",
+        metadata=bad_metadata,
+    )
+
+    # Check that _process_media_and_apply_mask was called for metadata with the sanitized dict
+    mock_process.assert_any_call(
+        data={"valid_key": "value"}, field="metadata", span=mock_otel_span
+    )
+
+    # Reset mock and test update method
+    mock_process.reset_mock()
+    bad_metadata_update = {
+        "another_valid": "value2",
+        "another_bad": "",
+        "another_none": None,
+    }
+
+    wrapper.update(metadata=bad_metadata_update)
+    mock_process.assert_any_call(
+        data={"another_valid": "value2"}, field="metadata", span=mock_otel_span
+    )