Disallow empty bands array in load_collection/load_stac

and add support for parameterized bands in `load_stac`

refs: #424, Open-EO/openeo-processes#372

CHANGELOG.md

@@ -13,9 +13,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `Connection.web_editor()` to build link to the openEO backend in the openEO Web Editor
 - Add support for `log_level` in `create_job()` and `execute_job()` ([#704](https://github.com/Open-EO/openeo-python-client/issues/704))
 - Add initial support for "geometry" dimension type in `CubeMetadata` ([#705](https://github.com/Open-EO/openeo-python-client/issues/705))
+- Add support for parameterized `bands` argument in `load_stac()`
 
 ### Changed
 
+- Raise exception when providing empty bands array to `load_collection`/`load_stac` ([#424](https://github.com/Open-EO/openeo-python-client/issues/424), [Open-EO/openeo-processes#372](https://github.com/Open-EO/openeo-processes/issues/372))
+
 ### Removed
 
 ### Fixed

openeo/rest/connection.py

@@ -1258,7 +1258,7 @@ def load_collection(
         collection_id: Union[str, Parameter],
         spatial_extent: Union[Dict[str, float], Parameter, None] = None,
         temporal_extent: Union[Sequence[InputDate], Parameter, str, None] = None,
-        bands: Union[None, List[str], Parameter] = None,
+        bands: Union[Iterable[str], Parameter, str, None] = None,
         properties: Union[
             None, Dict[str, Union[str, PGNode, Callable]], List[CollectionProperty], CollectionProperty
         ] = None,
@@ -1348,7 +1348,7 @@ def load_stac(
         url: str,
         spatial_extent: Union[Dict[str, float], Parameter, None] = None,
         temporal_extent: Union[Sequence[InputDate], Parameter, str, None] = None,
-        bands: Optional[List[str]] = None,
+        bands: Union[Iterable[str], Parameter, str, None] = None,
         properties: Optional[Dict[str, Union[str, PGNode, Callable]]] = None,
     ) -> DataCube:
         """

openeo/rest/datacube.py

@@ -145,7 +145,7 @@ def load_collection(
         connection: Optional[Connection] = None,
         spatial_extent: Union[Dict[str, float], Parameter, None] = None,
         temporal_extent: Union[Sequence[InputDate], Parameter, str, None] = None,
-        bands: Union[None, List[str], Parameter] = None,
+        bands: Union[Iterable[str], Parameter, str, None] = None,
         fetch_metadata: bool = True,
         properties: Union[
             None, Dict[str, Union[str, PGNode, typing.Callable]], List[CollectionProperty], CollectionProperty
@@ -198,10 +198,9 @@ def load_collection(
         metadata: Optional[CollectionMetadata] = (
             connection.collection_metadata(collection_id) if connection and fetch_metadata else None
         )
-        if bands:
-            if isinstance(bands, str):
-                bands = [bands]
-            elif isinstance(bands, Parameter):
+        if bands is not None:
+            bands = cls._get_bands(bands, process_id="load_collection")
+            if isinstance(bands, Parameter):
                 metadata = None
             if metadata:
                 bands = [b if isinstance(b, str) else metadata.band_dimension.band_name(b) for b in bands]
@@ -272,7 +271,7 @@ def load_stac(
         url: str,
         spatial_extent: Union[Dict[str, float], Parameter, None] = None,
         temporal_extent: Union[Sequence[InputDate], Parameter, str, None] = None,
-        bands: Optional[List[str]] = None,
+        bands: Union[Iterable[str], Parameter, str, None] = None,
         properties: Optional[Dict[str, Union[str, PGNode, Callable]]] = None,
         connection: Optional[Connection] = None,
     ) -> DataCube:
@@ -379,7 +378,8 @@ def load_stac(
             arguments["spatial_extent"] = spatial_extent
         if temporal_extent:
             arguments["temporal_extent"] = DataCube._get_temporal_extent(extent=temporal_extent)
-        if bands:
+        bands = cls._get_bands(bands, process_id="load_stac")
+        if bands is not None:
             arguments["bands"] = bands
         if properties:
             arguments["properties"] = {
@@ -388,7 +388,7 @@ def load_stac(
         graph = PGNode("load_stac", arguments=arguments)
         try:
             metadata = metadata_from_stac(url)
-            if bands:
+            if isinstance(bands, list):
                 # TODO: also apply spatial/temporal filters to metadata?
                 metadata = metadata.filter_bands(band_names=bands)
         except Exception:
@@ -429,6 +429,24 @@ def convertor(d: Any) -> Any:
                 get_temporal_extent(*args, start_date=start_date, end_date=end_date, extent=extent, convertor=convertor)
             )
 
+    @staticmethod
+    def _get_bands(
+        bands: Union[Iterable[str], Parameter, str, None], process_id: str
+    ) -> Union[None, List[str], Parameter]:
+        """Normalize band array for processes like load_collection, load_stac"""
+        if bands is None:
+            pass
+        elif isinstance(bands, str):
+            bands = [bands]
+        elif isinstance(bands, Parameter):
+            pass
+        else:
+            # Coerce to list
+            bands = list(bands)
+            if len(bands) == 0:
+                raise OpenEoClientException(f"Bands array should not be empty (process {process_id!r})")
+        return bands
+
     @openeo_process
     def filter_temporal(
         self,

tests/rest/datacube/test_datacube100.py

@@ -2308,6 +2308,34 @@ def test_load_collection_parameterized_bands(con100):
     }
 
 
+@pytest.mark.parametrize(
+    "bands",
+    [
+        ["B02", "B03"],
+        ("B02", "B03"),
+        iter(["B02", "B03"]),
+    ],
+)
+def test_load_collection_bands_iterable(con100, bands):
+    cube = con100.load_collection("S2", bands=bands)
+    assert get_download_graph(cube, drop_save_result=True) == {
+        "loadcollection1": {
+            "process_id": "load_collection",
+            "arguments": {
+                "id": "S2",
+                "spatial_extent": None,
+                "temporal_extent": None,
+                "bands": ["B02", "B03"],
+            },
+        },
+    }
+
+
+def test_load_collection_empty_bands_array(con100):
+    with pytest.raises(OpenEoClientException, match="Bands array should not be empty"):
+        _ = con100.load_collection("S2", bands=[])
+
+
 @pytest.mark.parametrize(
     ["spatial_extent", "temporal_extent", "spatial_name", "temporal_name"],
     [

tests/rest/test_connection.py

@@ -17,6 +17,7 @@
 
 import openeo
 from openeo import BatchJob
+from openeo.api.process import Parameter
 from openeo.capabilities import ApiVersionException
 from openeo.internal.graph_building import FlatGraphableMixin, PGNode
 from openeo.metadata import _PYSTAC_1_9_EXTENSION_INTERFACE, TemporalDimension
@@ -2681,6 +2682,51 @@ def test_load_stac_band_filtering(self, con120, tmp_path):
         cube = con120.load_stac(str(stac_path), bands=["B03", "B02"])
         assert cube.metadata.band_names == ["B03", "B02"]
 
+    @pytest.mark.parametrize(
+        "bands",
+        [
+            ["B02", "B03"],
+            ("B02", "B03"),
+            iter(["B02", "B03"]),
+        ],
+    )
+    def test_bands_iterable(self, con120, bands):
+        cube = con120.load_stac(
+            "https://provider.test/dataset",
+            bands=bands,
+        )
+        assert cube.flat_graph() == {
+            "loadstac1": {
+                "process_id": "load_stac",
+                "arguments": {
+                    "url": "https://provider.test/dataset",
+                    "bands": ["B02", "B03"],
+                },
+                "result": True,
+            }
+        }
+
+    def test_bands_empty(self, con120):
+        with pytest.raises(OpenEoClientException, match="Bands array should not be empty"):
+            _ = con120.load_stac("https://provider.test/dataset", bands=[])
+
+    def test_bands_parameterized(self, con120):
+        bands = Parameter(name="my_bands", schema={"type": "array", "items": {"type": "string"}})
+        cube = con120.load_stac(
+            "https://provider.test/dataset",
+            bands=bands,
+        )
+        assert cube.flat_graph() == {
+            "loadstac1": {
+                "process_id": "load_stac",
+                "arguments": {
+                    "url": "https://provider.test/dataset",
+                    "bands": {"from_parameter": "my_bands"},
+                },
+                "result": True,
+            }
+        }
+
 
 @pytest.mark.parametrize(
     "data",