Test a few corner cases of fetch_data

src/CSET/_workflow_utils/fetch_data.py

@@ -77,6 +77,8 @@ def get_file(self, file_path: str, output_dir: str) -> None:
         """
         file_paths = glob.glob(os.path.expanduser(file_path))
         logging.debug("Copying files:\n%s", "\n".join(file_paths))
+        if not file_paths:
+            logging.warning("file_path does not match any files: %s", file_path)
         for file in file_paths:
             try:
                 shutil.copy(file, output_dir)

tests/workflow_utils/test_fetch_data.py

@@ -15,6 +15,7 @@
 """Tests for fetch_data workflow utility."""
 
 import datetime
+from pathlib import Path
 
 import pytest
 
@@ -161,3 +162,24 @@ def test_FilesystemFileRetriever(tmp_path):
         ffr.get_file("tests/test_data/exeter_em*.nc", str(tmp_path))
     assert (tmp_path / "exeter_em01.nc").is_file()
     assert (tmp_path / "exeter_em02.nc").is_file()
+
+
+def test_FilesystemFileRetriever_no_files(tmp_path, caplog):
+    """Test warning when no files match the requested path."""
+    with fetch_data.FilesystemFileRetriever() as ffr:
+        # Should warn, but not error.
+        ffr.get_file("/non-existent/file.nc", str(tmp_path))
+    log_record = caplog.records[0]
+    assert log_record.levelname == "WARNING"
+    assert log_record.message.startswith("file_path does not match any files:")
+
+
+def test_FilesystemFileRetriever_copy_error(caplog):
+    """Test warning when file copy errors."""
+    with fetch_data.FilesystemFileRetriever() as ffr:
+        # Please don't run as root.
+        ffr.get_file("tests/test_data/air_temp.nc", "/usr/bin")
+    assert not Path("/usr/bin/air_temp.nc").is_file()
+    log_record = caplog.records[0]
+    assert log_record.levelname == "WARNING"
+    assert log_record.message.startswith("Failed to copy")