Use '%20' for encoding spaces in query parameters.

httpx/_urlparse.py

@@ -433,3 +433,19 @@ def quote(string: str, safe: str = "/") -> str:
     return "".join(
         [char if char in NON_ESCAPED_CHARS else percent_encode(char) for char in string]
     )
+
+
+def urlencode(items: typing.List[typing.Tuple[str, str]]) -> str:
+    # We can use a much simpler version of the stdlib urlencode here because
+    # we don't need to handle a bunch of different typing cases, such as bytes vs str.
+    #
+    # https://github.com/python/cpython/blob/b2f7b2ef0b5421e01efb8c7bee2ef95d3bab77eb/Lib/urllib/parse.py#L926
+    #
+    # Note that we use '%20' encoding for spaces, and treat '/' as a safe
+    # character. This means our query params have the same escaping as other
+    # characters in the URL path. This is slightly different to `requests`,
+    # but is the behaviour that browsers use.
+    #
+    # See https://github.com/encode/httpx/issues/2536 and
+    # https://docs.python.org/3/library/urllib.parse.html#urllib.parse.urlencode
+    return "&".join([quote(k) + "=" + quote(v) for k, v in items])

httpx/_urls.py

@@ -1,10 +1,10 @@
 import typing
-from urllib.parse import parse_qs, unquote, urlencode
+from urllib.parse import parse_qs, unquote
 
 import idna
 
 from ._types import PrimitiveData, QueryParamTypes, RawURL, URLTypes
-from ._urlparse import urlparse
+from ._urlparse import urlencode, urlparse
 from ._utils import primitive_value_to_str
 
 
@@ -616,6 +616,13 @@ def __eq__(self, other: typing.Any) -> bool:
         return sorted(self.multi_items()) == sorted(other.multi_items())
 
     def __str__(self) -> str:
+        """
+        Note that we use '%20' encoding for spaces, and treat '/' as a safe
+        character.
+
+        See https://github.com/encode/httpx/issues/2536 and
+        https://docs.python.org/3/library/urllib.parse.html#urllib.parse.urlencode
+        """
         return urlencode(self.multi_items())
 
     def __repr__(self) -> str:

tests/models/test_url.py

@@ -350,6 +350,22 @@ def test_url_with_empty_query():
     assert url.raw_path == b"/path?"
 
 
+def test_url_query_encoding():
+    """
+    URL query parameters should use '%20' to encoding spaces,
+    and should treat '/' as a safe character. This behaviour differs
+    across clients, but we're matching browser behaviour here.
+
+    See https://github.com/encode/httpx/issues/2536
+    and https://github.com/encode/httpx/discussions/2460
+    """
+    url = httpx.URL("https://www.example.com/?a=b c&d=e/f")
+    assert url.raw_path == b"/?a=b%20c&d=e/f"
+
+    url = httpx.URL("https://www.example.com/", params={"a": "b c", "d": "e/f"})
+    assert url.raw_path == b"/?a=b%20c&d=e/f"
+
+
 def test_url_with_url_encoded_path():
     url = httpx.URL("https://www.example.com/path%20to%20somewhere")
     assert url.path == "/path to somewhere"