Remove xcengine.util dependency on pystac

write_stac now fails silently if pystac is not available.

Author: pont-us

test/test_util.py

@@ -85,6 +85,29 @@ def test_write_stac(tmp_path, dataset, write_datasets, pre_existing_catalog):
         }
 
 
+orig_import = __import__
+def import_mock(name, *args):
+    if name == 'pystac':
+        raise ModuleNotFoundError("No module named 'pystac'")
+    return orig_import(name, *args)
+
+
+def test_write_stac_no_pystac(tmp_path, dataset):
+    # Import hooks are the recommended "clean" way to do this, but don't work
+    # in this case.
+    with mock.patch('builtins.__import__', side_effect=import_mock):
+        # pytest imports xcengine.util long before we can patch __import__,
+        # so we delete pystac from util's namespace (if present) instead.
+        # This gives a NameError on access rather than a ModuleNotFoundError
+        # on import, but the important thing is to break any implementation
+        # that tries to import pystac without checking if it's available.
+        import xcengine.util
+        xcengine.util.__dict__.pop("pystac", None)
+        from xcengine.util import write_stac
+        write_stac({"ds1": dataset}, tmp_path)
+        # We want nothing to happen here, so no explicit assertions.
+
+
 @pytest.mark.parametrize("eoap_mode", [False, True])
 @pytest.mark.parametrize("ds2_format", [None, "zarr", "netcdf"])
 def test_save_datasets(tmp_path, dataset, eoap_mode, ds2_format):

xcengine/util.py

@@ -8,11 +8,9 @@
 import shutil
 from typing import NamedTuple, Mapping
 
-import pystac
 import xarray as xr
 from xarray import Dataset
 
-
 def clear_directory(directory: pathlib.Path) -> None:
     for path in directory.iterdir():
         if path.is_dir():
@@ -24,6 +22,12 @@ def clear_directory(directory: pathlib.Path) -> None:
 def write_stac(
     datasets: Mapping[str, xr.Dataset], stac_root: pathlib.Path
 ) -> None:
+    try:
+        import pystac
+    except ModuleNotFoundError:
+        # If pystac isn't present, we assume that stage-out is not required
+        # and exit quietly.
+        return
     catalog_path = stac_root / "catalog.json"
     if catalog_path.exists():
         # Assume that the user code generated its own stage-out data