Closes #297

alchemiscale/interface/api.py

@@ -96,7 +96,14 @@
     n4js: Neo4jStore = Depends(get_n4js_depends),
     token: TokenData = Depends(get_token_data_depends),
 ):
-    sk = ScopedKey.from_str(scoped_key)
+    try:
+        sk = ScopedKey.from_str(scoped_key)
+    except ValueError as e:
+        raise HTTPException(
+            status_code=http_status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail=e.args[0],
+        )
+
     validate_scopes(sk.scope, token)
 
     return n4js.check_existence(scoped_key=sk)

alchemiscale/interface/client.py

@@ -88,7 +88,7 @@ def get_scoped_key(self, obj: GufeTokenizable, scope: Scope) -> ScopedKey:
                 "Scope for a ScopedKey must be specific; it cannot contain wildcards."
             )
 
-    def check_exists(self, scoped_key: ScopedKey) -> bool:
+    def check_exists(self, scoped_key: ScopedKey | str) -> bool:
         """Returns ``True`` if the given ScopedKey represents an object in the database."""
         return self._get_resource(f"/exists/{scoped_key}")
 

alchemiscale/models.py

@@ -151,7 +151,11 @@
 
     @classmethod
     def from_str(cls, string):
-        prefix, token, org, campaign, project = string.split("-")
+        try:
+            prefix, token, org, campaign, project = string.split("-")
+        except ValueError:
+            raise ValueError("input does not appear to be a `ScopedKey`")
+
         gufe_key = GufeKey(f"{prefix}-{token}")
 
         return cls(gufe_key=gufe_key, org=org, campaign=campaign, project=project)

alchemiscale/tests/integration/interface/client/test_client.py

@@ -86,10 +86,38 @@ def test_create_network(
         network_sks = user_client.query_networks()
         assert an_sk in network_sks
 
+        assert user_client.check_exists(an_sk)
+
         # TODO: make a network in a scope that doesn't have any components in
         # common with an existing network
         # user_client.create_network(
 
+    def test_check_exists(
+        self,
+        scope_test,
+        n4js_preloaded,
+        user_client: client.AlchemiscaleClient,
+        network_tyk2,
+    ):
+        an_sks = user_client.query_networks()
+
+        # check that a known existing AlchemicalNetwork exists
+        assert user_client.check_exists(an_sks[0])
+
+        # check that an AlchemicalNetwork that doesn't exist shows as not existing
+        an_sk = an_sks[0]
+        an_sk_nonexistent = ScopedKey(
+            gufe_key=GufeKey("AlchemicalNetwork-lol"), **scope_test.dict()
+        )
+        assert not user_client.check_exists(an_sk_nonexistent)
+
+        # check that we get an exception when we try a malformed key
+        with pytest.raises(
+            AlchemiscaleClientError,
+            match="Status Code 422 : Unprocessable Entity : input does not appear to be a `ScopedKey`",
+        ):
+            user_client.check_exists("lol")
+
     @pytest.mark.parametrize(("state",), [[state.value] for state in NetworkStateEnum])
     def test_set_network_state(
         self,