standardize requests to optimize caching

earthkit/data/sources/cds.py

@@ -137,26 +137,32 @@ def retrieve(target, args):
     @normalize("date", "date-list(%Y-%m-%d)")
     @normalize("area", "bounding-box(list)")
     def _normalize_request(**kwargs):
-        return kwargs
+        request = {}
+        for k, v in sorted(kwargs.items()):
+            v = ensure_iterable(v)
+            if k not in ("area", "grid"):
+                v = sorted(v)
+            request[k] = v[0] if len(v) == 1 else v
+        return request
 
     @cached_property
     def requests(self):
         requests = []
-        for arg in self._args:
-            request = self._normalize_request(**arg)
-            split_on = request.pop("split_on", None)
-            if split_on is None:
+        for request in self._args:
+            split_on = request.pop("split_on", {})
+            if not isinstance(split_on, dict):
+                split_on = {k: 1 for k in ensure_iterable(split_on) if k is not None}
+            if not split_on:
                 requests.append(request)
                 continue
 
-            if not isinstance(split_on, dict):
-                split_on = {k: 1 for k in ensure_iterable(split_on)}
+            request = self._normalize_request(**request)
             for values in itertools.product(
                 *[batched(ensure_iterable(request[k]), v) for k, v in split_on.items()]
             ):
                 subrequest = dict(zip(split_on, values))
                 requests.append(request | subrequest)
-        return requests
+        return [self._normalize_request(**request) for request in requests]
 
 
 source = CdsRetriever

tests/sources/test_cds.py

@@ -120,6 +120,36 @@ def test_cds_grib_multi_var_date(date, expected_date):
     assert s.metadata("date") == expected_date
 
 
+@pytest.mark.long_test
+@pytest.mark.download
+@pytest.mark.skipif(NO_CDS, reason="No access to CDS")
+@pytest.mark.parametrize(
+    "variable1,variable2,expected_vars",
+    (
+        ("2t", ["2t"], {"t2m"}),
+        (["2t", "msl"], ["msl", "2t"], {"t2m", "msl"}),
+    ),
+)
+def test_cds_normalized_request(variable1, variable2, expected_vars):
+    base_request = dict(
+        product_type="reanalysis",
+        area=[50, -50, 20, 50],
+        grid=[2, 1],
+        date="2012-12-12",
+        time="12:00",
+    )
+    s1 = from_source(
+        "cds", "reanalysis-era5-single-levels", variable=variable1, **base_request
+    )
+    s2 = from_source(
+        "cds", "reanalysis-era5-single-levels", variable=variable2, **base_request
+    )
+    assert s1.path == s2.path
+    assert set(s1.to_xarray().data_vars) == expected_vars
+    assert s1.to_xarray()["longitude"].values.tolist() == list(range(-50, 51, 2))
+    assert s1.to_xarray()["latitude"].values.tolist() == list(range(50, 19, -1))
+
+
 @pytest.mark.long_test
 @pytest.mark.download
 @pytest.mark.skipif(NO_CDS, reason="No access to CDS")