fix(ingest/looker): Ignore fields with empty column name to not generate invalid field urns (#14338)

metadata-ingestion/src/datahub/ingestion/source/looker/looker_common.py

@@ -379,6 +379,14 @@ class ExploreUpstreamViewField:
                 : -(len(self.field.field_group_variant.lower()) + 1)
             ]
 
+        # Validate that field_name is not empty to prevent invalid schema field URNs
+        if not field_name or not field_name.strip():
+            logger.warning(
+                f"Empty field name detected for field '{self.field.name}' in explore '{self.explore.name}'. "
+                f"Skipping field to prevent invalid schema field URN generation."
+            )
+            return None
+
         assert view_name  # for lint false positive
 
         project_include: ProjectInclude = ProjectInclude(
@@ -1351,7 +1359,25 @@ class LookerExplore:
             fine_grained_lineages = []
             if config.extract_column_level_lineage:
                 for field in self.fields or []:
+                    # Skip creating fine-grained lineage for empty field names to prevent invalid schema field URNs
+                    if not field.name or not field.name.strip():
+                        logger.warning(
+                            f"Skipping fine-grained lineage for field with empty name in explore '{self.name}'"
+                        )
+                        continue
+
                     for upstream_column_ref in field.upstream_fields:
+                        # Skip creating fine-grained lineage for empty column names to prevent invalid schema field URNs
+                        if (
+                            not upstream_column_ref.column
+                            or not upstream_column_ref.column.strip()
+                        ):
+                            logger.warning(
+                                f"Skipping some fine-grained lineage for field '{field.name}' in explore '{self.name}' "
+                                f"due to empty upstream column name in table '{upstream_column_ref.table}'"
+                            )
+                            continue
+
                         fine_grained_lineages.append(
                             FineGrainedLineageClass(
                                 upstreamType=FineGrainedLineageUpstreamType.FIELD_SET,

metadata-ingestion/tests/unit/looker/test_looker_common.py

@@ -0,0 +1,93 @@
+import logging
+from unittest.mock import MagicMock
+
+import pytest
+from looker_sdk.sdk.api40.models import LookmlModelExplore, LookmlModelExploreField
+
+from datahub.ingestion.source.looker.looker_common import ExploreUpstreamViewField
+from datahub.ingestion.source.looker.looker_config import LookerCommonConfig
+
+
+class TestExploreUpstreamViewFieldFormFieldName:
+    """Test empty field name validation in _form_field_name method."""
+
+    @pytest.mark.parametrize(
+        "field_name",
+        [
+            "test_view.",  # Empty after dot
+            "test_view.   ",  # Whitespace after dot
+        ],
+    )
+    def test_returns_none_for_empty_field_name(self, field_name, caplog):
+        """Test that empty field names return None and log warnings."""
+        explore = LookmlModelExplore(name="test_explore")
+        field = LookmlModelExploreField(
+            name=field_name, type="string", original_view=None, field_group_variant=None
+        )
+        upstream_field = ExploreUpstreamViewField(field=field, explore=explore)
+        config = MagicMock(spec=LookerCommonConfig)
+
+        with caplog.at_level(logging.WARNING):
+            result = upstream_field._form_field_name(
+                view_project_map={},
+                explore_project_name="test_project",
+                model_name="test_model",
+                upstream_views_file_path={},
+                config=config,
+            )
+
+            assert result is None
+            assert "Empty field name detected" in caplog.text
+            assert field_name in caplog.text
+            assert "test_explore" in caplog.text
+
+    def test_returns_none_for_invalid_field_format(self):
+        """Test that fields without proper view.field format return None."""
+        explore = LookmlModelExplore(name="test_explore")
+        field = LookmlModelExploreField(
+            name="just_field_name",  # No dot separator
+            type="string",
+            original_view=None,
+            field_group_variant=None,
+        )
+        upstream_field = ExploreUpstreamViewField(field=field, explore=explore)
+
+        result = upstream_field._form_field_name(
+            view_project_map={},
+            explore_project_name="test_project",
+            model_name="test_model",
+            upstream_views_file_path={},
+            config=MagicMock(spec=LookerCommonConfig),
+        )
+
+        assert result is None
+
+    def test_variant_removal_causing_empty_name(self, caplog):
+        """Test that variant removal resulting in empty name returns None."""
+        explore = LookmlModelExplore(name="test_explore")
+        # In Looker, dimension groups create fields with variants like "created_date_month", "created_date_year"
+        # This test simulates a pathological case where:
+        # - field name is "test_view.month" (after splitting by ".", field_name becomes "month")
+        # - field_group_variant is "month"
+        # - When remove_variant=True, it removes "_month" from "month", resulting in empty string
+        # - This should be handled gracefully by returning None and logging a warning
+        field = LookmlModelExploreField(
+            name="test_view.month",
+            type="string",
+            original_view=None,
+            field_group_variant="month",  # When removed with underscore ("_month"), leaves empty field name
+        )
+        upstream_field = ExploreUpstreamViewField(field=field, explore=explore)
+
+        with caplog.at_level(logging.WARNING):
+            result = upstream_field._form_field_name(
+                view_project_map={},
+                explore_project_name="test_project",
+                model_name="test_model",
+                upstream_views_file_path={},
+                config=MagicMock(spec=LookerCommonConfig),
+                remove_variant=True,
+            )
+
+            assert result is None
+            assert "Empty field name detected" in caplog.text