fix tests

stripe/_api_requestor.py

@@ -20,7 +20,7 @@
     Unpack,
 )
 import uuid
-from urllib.parse import urlsplit, urlunsplit
+from urllib.parse import urlsplit, urlunsplit, parse_qs
 
 # breaking circular dependency
 import stripe  # noqa: IMP101
@@ -561,12 +561,19 @@ def _args_for_request_with_retries(
             # if we're sending params in the querystring, then we have to make sure we're not
             # duplicating anything we got back from the server already (like in a list iterator)
             # so, we parse the querystring the server sends back so we can merge with what we (or the user) are trying to send
-            # note: server sends back "expand[]" but users supply "expand", so we have to match them up
-            existing_params = {
-                "expand" if k == "expand[]" else k: v
-                for k, v in parse_qs(urlsplit(url).query).items()
-            }
+            existing_params = {}
+            for k, v in parse_qs(urlsplit(url).query).items():
+                # note: server sends back "expand[]" but users supply "expand", so we strip the brackets from the key name
+                if k.endswith("[]"):
+                    existing_params[k[:-2]] = v
+                else:
+                    # all querystrings are pulled out as lists.
+                    # We want to keep the querystrings that actually are lists, but flatten the ones that are single values
+                    existing_params[k] = v[0] if len(v) == 1 else v
+
             # if a user is expanding something that wasn't expanded before, add (and deduplicate) it
+            # this could theoretically work for other lists that we want to merge too, but that doesn't seem to be a use case
+            # it never would have worked before, so I think we can start with `expand` and go from there
             if "expand" in existing_params and "expand" in params:
                 params["expand"] = list(  # type:ignore - this is a dict
                     set([*existing_params["expand"], *params["expand"]])

tests/test_api_requestor.py

@@ -245,16 +245,17 @@ def test_ordereddict_encoding(self):
 
     def test_url_construction(self, requestor, http_client_mock):
         CASES = (
-            ("%s?foo=bar" % stripe.api_base, "", {"foo": "bar"}),
-            ("%s?foo=bar" % stripe.api_base, "?", {"foo": "bar"}),
+            (f"{stripe.api_base}?foo=bar", "", {"foo": "bar"}),
+            (f"{stripe.api_base}?foo=bar", "?", {"foo": "bar"}),
             (stripe.api_base, "", {}),
             (
-                "%s/%%20spaced?foo=bar%%24&baz=5" % stripe.api_base,
+                f"{stripe.api_base}/%20spaced?baz=5&foo=bar%24",
                 "/%20spaced?foo=bar%24",
                 {"baz": "5"},
             ),
+            # duplicate query params keys should be deduped
             (
-                "%s?foo=bar&foo=bar" % stripe.api_base,
+                f"{stripe.api_base}?foo=bar",
                 "?foo=bar",
                 {"foo": "bar"},
             ),