Better error message when trying to open a Collection with Client.open

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Search `filter-lang` defaults to `cql2-json` instead of `cql-json` [#169](https://github.com/stac-utils/pystac-client/pull/169)
 - Search `filter-lang` will be set to `cql2-json` if the `filter` is a dict, or `cql2-text` if it is a string [#169](https://github.com/stac-utils/pystac-client/pull/169)
 - Search parameter `intersects` is now typed to only accept a str, dict, or object that implements `__geo_interface__` [#169](https://github.com/stac-utils/pystac-client/pull/169)
+- Better error message when trying to open a Collection with `Client.open` [#222](https://github.com/stac-utils/pystac-client/pull/222)
 
 
 ### Deprecated

pystac_client/client.py

@@ -6,6 +6,7 @@
 
 from pystac_client.collection_client import CollectionClient
 from pystac_client.conformance import ConformanceClasses
+from pystac_client.errors import ClientTypeError
 from pystac_client.exceptions import APIError
 from pystac_client.item_search import ItemSearch
 from pystac_client.stac_api_io import StacApiIO
@@ -93,6 +94,25 @@ def from_file(
 
         return cat
 
+    @classmethod
+    def from_dict(
+        cls,
+        d: Dict[str, Any],
+        href: Optional[str] = None,
+        root: Optional[pystac.Catalog] = None,
+        migrate: bool = False,
+        preserve_dict: bool = True,
+    ) -> "Client":
+        try:
+            return super().from_dict(
+                d=d, href=href, root=root, migrate=migrate, preserve_dict=preserve_dict
+            )
+        except pystac.STACTypeError:
+            raise ClientTypeError(
+                f"Could not open Client (href={href}), "
+                f"expected type=Catalog, found type={d.get('type', None)}"
+            )
+
     @lru_cache()
     def get_collection(self, collection_id: str) -> CollectionClient:
         """Get a single collection from this Catalog/API

pystac_client/errors.py

@@ -0,0 +1,4 @@
+class ClientTypeError(Exception):
+    """Raised when trying to open a Client on a non-catalog STAC Object."""
+
+    pass

tests/test_client.py

@@ -11,6 +11,7 @@
 
 from pystac_client import Client
 from pystac_client.conformance import ConformanceClasses
+from pystac_client.errors import ClientTypeError
 
 from .helpers import STAC_URLS, TEST_DATA, read_data_file
 
@@ -326,6 +327,11 @@ def test_get_collections_without_conformance(self, requests_mock):
         assert len(history) == 2
         assert history[1].url == pc_collection_href
 
+    def test_opening_a_collection(self) -> None:
+        path = str(TEST_DATA / "planetary-computer-aster-l1t-collection.json")
+        with pytest.raises(ClientTypeError):
+            Client.open(path)
+
 
 class TestAPISearch:
     @pytest.fixture(scope="function")