fix: raise clear error when all records are dropped during generation

packages/data-designer/src/data_designer/interface/data_designer.py

@@ -213,11 +213,25 @@ def create(
             raise DataDesignerGenerationError(f"🛑 Error generating dataset: {e}")
 
         try:
-            profiler = self._create_dataset_profiler(config_builder, resource_provider)
-            analysis = profiler.profile_dataset(
-                num_records,
-                builder.artifact_storage.load_dataset_with_dropped_columns(),
+            dataset_for_profiler = builder.artifact_storage.load_dataset_with_dropped_columns()
+        except Exception as e:
+            raise DataDesignerGenerationError(
+                f"🛑 Failed to load generated dataset — all records may have been dropped "
+                f"due to generation failures. Check the warnings above for details. Original error: {e}"
             )
+
+        # Defensive: the batch manager skips writing when the buffer is empty, so in
+        # practice load_dataset_with_dropped_columns() would raise before returning a
+        # zero-row DataFrame. This guard protects against future changes to that contract.
+        if len(dataset_for_profiler) == 0:
+            raise DataDesignerGenerationError(
+                "🛑 Dataset is empty — all records were dropped due to generation failures. "
+                "Check the warnings above for details on which columns failed."
+            )
+
+        try:
+            profiler = self._create_dataset_profiler(config_builder, resource_provider)
+            analysis = profiler.profile_dataset(num_records, dataset_for_profiler)
         except Exception as e:
             raise DataDesignerProfilingError(f"🛑 Error profiling dataset: {e}")
 
@@ -267,6 +281,12 @@ def preview(
         except Exception as e:
             raise DataDesignerGenerationError(f"🛑 Error generating preview dataset: {e}")
 
+        if len(processed_dataset) == 0:
+            raise DataDesignerGenerationError(
+                "🛑 Dataset is empty — all records were dropped due to generation or processing failures. "
+                "Check the warnings above for details on which columns failed."
+            )
+
         dropped_columns = raw_dataset.columns.difference(processed_dataset.columns)
         if len(dropped_columns) > 0:
             dataset_for_profiler = lazy.pd.concat([processed_dataset, raw_dataset[dropped_columns]], axis=1)
@@ -283,11 +303,7 @@ def preview(
         for name in builder.artifact_storage.list_processor_names():
             processor_artifacts[name] = builder.artifact_storage.load_processor_dataset(name).to_dict(orient="records")
 
-        if (
-            len(processed_dataset) > 0
-            and isinstance(analysis, DatasetProfilerResults)
-            and len(analysis.column_statistics) > 0
-        ):
+        if isinstance(analysis, DatasetProfilerResults) and len(analysis.column_statistics) > 0:
             logger.info(f"{RandomEmoji.success()} Preview complete!")
 
         # Create dataset metadata from the resource provider

packages/data-designer/tests/interface/test_data_designer.py

@@ -304,6 +304,73 @@ def test_preview_raises_error_when_profiler_fails(
             data_designer.preview(stub_sampler_only_config_builder, num_records=3)
 
 
+def test_create_raises_generation_error_when_dataset_is_empty(
+    stub_artifact_path, stub_model_providers, stub_sampler_only_config_builder, stub_managed_assets_path
+):
+    """When all records are dropped during generation, create should raise
+    DataDesignerGenerationError with a clear message instead of a misleading profiler error.
+    """
+    data_designer = DataDesigner(
+        artifact_path=stub_artifact_path,
+        model_providers=stub_model_providers,
+        secret_resolver=PlaintextResolver(),
+        managed_assets_path=stub_managed_assets_path,
+    )
+
+    with patch(
+        "data_designer.engine.storage.artifact_storage.ArtifactStorage.load_dataset_with_dropped_columns",
+        return_value=lazy.pd.DataFrame(),
+    ):
+        with pytest.raises(DataDesignerGenerationError, match="Dataset is empty"):
+            data_designer.create(stub_sampler_only_config_builder, num_records=1)
+
+
+def test_create_raises_generation_error_when_load_dataset_fails(
+    stub_artifact_path: Path,
+    stub_model_providers: list[ModelProvider],
+    stub_sampler_only_config_builder: DataDesignerConfigBuilder,
+    stub_managed_assets_path: Path,
+) -> None:
+    """When no parquet was written (e.g. all records dropped), load_dataset_with_dropped_columns
+    raises an exception. create() should surface this as DataDesignerGenerationError, not
+    DataDesignerProfilingError.
+    """
+    data_designer = DataDesigner(
+        artifact_path=stub_artifact_path,
+        model_providers=stub_model_providers,
+        secret_resolver=PlaintextResolver(),
+        managed_assets_path=stub_managed_assets_path,
+    )
+
+    with patch(
+        "data_designer.engine.storage.artifact_storage.ArtifactStorage.load_dataset_with_dropped_columns",
+        side_effect=FileNotFoundError("No parquet files found"),
+    ):
+        with pytest.raises(DataDesignerGenerationError, match="Failed to load generated dataset"):
+            data_designer.create(stub_sampler_only_config_builder, num_records=1)
+
+
+def test_preview_raises_generation_error_when_dataset_is_empty(
+    stub_artifact_path, stub_model_providers, stub_sampler_only_config_builder, stub_managed_assets_path
+):
+    """When all records are dropped during generation, preview should raise
+    DataDesignerGenerationError with a clear message instead of a misleading profiler error.
+    """
+    data_designer = DataDesigner(
+        artifact_path=stub_artifact_path,
+        model_providers=stub_model_providers,
+        secret_resolver=PlaintextResolver(),
+        managed_assets_path=stub_managed_assets_path,
+    )
+
+    with patch(
+        "data_designer.engine.dataset_builders.column_wise_builder.ColumnWiseDatasetBuilder.process_preview",
+        return_value=lazy.pd.DataFrame(),
+    ):
+        with pytest.raises(DataDesignerGenerationError, match="Dataset is empty"):
+            data_designer.preview(stub_sampler_only_config_builder, num_records=1)
+
+
 def test_preview_with_dropped_columns(
     stub_artifact_path, stub_model_providers, stub_model_configs, stub_managed_assets_path
 ):