Tweak error message

Signed-off-by: Mike Knepper <mknepper@nvidia.com>

Author: mikeknep

packages/data_designer_nemo/src/data_designer_nemo/seed.py

@@ -102,8 +102,16 @@ async def _validate_seed_from_files_service(
             f"An unexpected error occurred while listing path {fragment!r} in fileset {fully_qualified_fileset_name!r}: {e}"
         ) from e
 
+    # A path that resolves to no files provides nothing to seed from, so it is
+    # invalid regardless of whether the path itself exists. A FilesetFileSeedSource
+    # points at a single file, while the directory-style sources enumerate files
+    # under a directory; tailor the message accordingly.
     if not response.data:
-        raise NDDInvalidConfigError(f"Path {fragment!r} not found in fileset {fully_qualified_fileset_name!r}")
+        if isinstance(seed_source, FilesetFileSeedSource):
+            raise NDDInvalidConfigError(f"File {fragment!r} not found in fileset {fully_qualified_fileset_name!r}")
+        raise NDDInvalidConfigError(
+            f"Path {fragment!r} in fileset {fully_qualified_fileset_name!r} contains no files to use as seed data"
+        )
 
     return canonical_root
 

packages/data_designer_nemo/tests/unit/test_remote_filesystem_seeds.py

@@ -9,7 +9,9 @@
 import pytest
 from data_designer.engine.resources.seed_reader import DirectorySeedReader, FileContentsSeedReader
 from data_designer_nemo.context import RemoteDataDesignerContext
-from data_designer_nemo.seed import validate_seed
+from data_designer_nemo.errors import NDDInvalidConfigError
+from data_designer_nemo.fileset_file_seed_source import FilesetFileSeedSource
+from data_designer_nemo.seed import _validate_seed_from_files_service, validate_seed
 from nemo_platform import AsyncNeMoPlatform
 
 
@@ -35,3 +37,31 @@ async def test_validate_seed_returns_canonical_validated_filesystem_root() -> No
     assert validated_root == "default/docs#corpus"
     sdk.files.filesets.retrieve.assert_awaited_once_with(name="docs", workspace="default")
     sdk.files.list.assert_awaited_once_with(remote_path="corpus", fileset="docs", workspace="default")
+
+
+@pytest.mark.asyncio
+async def test_validate_seed_rejects_path_with_no_files() -> None:
+    sdk = AsyncMock(spec=AsyncNeMoPlatform)
+    sdk.files.filesets.retrieve = AsyncMock()
+    sdk.files.list = AsyncMock(return_value=Mock(data=[]))
+
+    builder = dd.DataDesignerConfigBuilder()
+    builder.with_seed_dataset(dd.FileContentsSeedSource(path="docs#corpus", file_pattern="*.md"))
+    config = builder.build()
+
+    with pytest.raises(NDDInvalidConfigError, match="contains no files to use as seed data"):
+        await validate_seed(config, "default", sdk, is_local=False)
+
+
+@pytest.mark.asyncio
+async def test_validate_seed_reports_missing_fileset_file() -> None:
+    # FilesetFileSeedSource points at a single file, so the error should say "File ... not found"
+    # rather than the directory-style "contains no files" message.
+    sdk = AsyncMock(spec=AsyncNeMoPlatform)
+    sdk.files.filesets.retrieve = AsyncMock()
+    sdk.files.list = AsyncMock(return_value=Mock(data=[]))
+
+    seed_source = FilesetFileSeedSource(path="docs#corpus/missing.parquet")
+
+    with pytest.raises(NDDInvalidConfigError, match=r"File 'corpus/missing.parquet' not found"):
+        await _validate_seed_from_files_service(seed_source, "default", sdk)