From ff93a011a44f4a76015e4866d01ff79a6afe350a Mon Sep 17 00:00:00 2001
From: Tom Christie <tom@tomchristie.com>
Date: Thu, 16 Jul 2020 11:16:29 +0100
Subject: [PATCH] Support QueryParams(None) (#1060)

---
 httpx/_client.py                 | 3 ---
 httpx/_models.py                 | 2 +-
 httpx/_types.py                  | 1 +
 tests/models/test_queryparams.py | 3 +++
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/httpx/_client.py b/httpx/_client.py
index 35d0bd0fe5..80a2bb03c3 100644
--- a/httpx/_client.py
+++ b/httpx/_client.py
@@ -73,9 +73,6 @@ def __init__(
         else:
             self.base_url = URL(base_url)
 
-        if params is None:
-            params = {}
-
         self.auth = auth
         self._params = QueryParams(params)
         self._headers = Headers(headers)
diff --git a/httpx/_models.py b/httpx/_models.py
index bf5f6d1cdd..1ab162cd65 100644
--- a/httpx/_models.py
+++ b/httpx/_models.py
@@ -287,7 +287,7 @@ def __init__(self, *args: QueryParamTypes, **kwargs: typing.Any) -> None:
         value = args[0] if args else kwargs
 
         items: typing.Sequence[typing.Tuple[str, PrimitiveData]]
-        if isinstance(value, str):
+        if value is None or isinstance(value, str):
             items = parse_qsl(value)
         elif isinstance(value, QueryParams):
             items = value.multi_items()
diff --git a/httpx/_types.py b/httpx/_types.py
index d2fc098e24..bfce5650da 100644
--- a/httpx/_types.py
+++ b/httpx/_types.py
@@ -34,6 +34,7 @@
     Mapping[str, Union[PrimitiveData, Sequence[PrimitiveData]]],
     List[Tuple[str, PrimitiveData]],
     str,
+    None,
 ]
 
 HeaderTypes = Union[
diff --git a/tests/models/test_queryparams.py b/tests/models/test_queryparams.py
index 0b0101cb31..99f193f86d 100644
--- a/tests/models/test_queryparams.py
+++ b/tests/models/test_queryparams.py
@@ -44,6 +44,9 @@ def test_queryparams(source):
 
 
 def test_queryparam_types():
+    q = QueryParams(None)
+    assert str(q) == ""
+
     q = QueryParams({"a": True})
     assert str(q) == "a=true"