Correct type hints for parse_string(s)_from_args.

synapse/http/servlet.py

@@ -15,10 +15,12 @@
 """ This module contains base REST classes for constructing REST servlets. """
 
 import logging
-from typing import Iterable, List, Optional, Union, overload
+from typing import Dict, Iterable, List, Optional, Union, overload
 
 from typing_extensions import Literal
 
+from twisted.web.server import Request
+
 from synapse.api.errors import Codes, SynapseError
 from synapse.util import json_decoder
 
@@ -108,6 +110,60 @@ def parse_boolean_from_args(args, name, default=None, required=False):
             return default
 
 
+@overload
+def parse_bytes(
+    request: Request,
+    name: str,
+    default: Literal[None] = None,
+    required: Literal[True] = True,
+) -> bytes:
+    ...
+
+
+@overload
+def parse_bytes(
+    request: Request,
+    name: str,
+    default: Optional[bytes] = None,
+    required: bool = False,
+) -> Optional[bytes]:
+    ...
+
+
+def parse_bytes(
+    request: Request,
+    name: str,
+    default: Optional[bytes] = None,
+    required: bool = False,
+) -> Optional[bytes]:
+    """
+    Parse a string parameter as bytes from the request query string.
+
+    Args:
+        request: the twisted HTTP request.
+        name: the name of the query parameter.
+        default: value to use if the parameter is absent,
+            defaults to None. Must be bytes if encoding is None.
+        required: whether to raise a 400 SynapseError if the
+            parameter is absent, defaults to False.
+    Returns:
+        Bytes or the default value.
+
+    Raises:
+        SynapseError if the parameter is absent and required.
+    """
+    args = request.args  # type: Dict[bytes, List[bytes]]  # type: ignore
+    name_bytes = name.encode("ascii")
+
+    if name_bytes in args:
+        return args[name_bytes][0]
+    elif required:
+        message = "Missing string query parameter %s" % (name,)
+        raise SynapseError(400, message, errcode=Codes.MISSING_PARAM)
+
+    return default
+
+
 def parse_string(
     request,
     name: Union[bytes, str],

synapse/rest/client/v1/login.py

@@ -25,6 +25,7 @@
 from synapse.http.server import HttpServer, finish_request
 from synapse.http.servlet import (
     RestServlet,
+    parse_bytes,
     parse_json_object_from_request,
     parse_string,
 )
@@ -437,9 +438,7 @@ async def on_GET(
             finish_request(request)
             return
 
-        client_redirect_url = parse_string(
-            request, "redirectUrl", required=True, encoding=None
-        )
+        client_redirect_url = parse_bytes(request, "redirectUrl", required=True)
         sso_url = await self._sso_handler.handle_redirect_request(
             request,
             client_redirect_url,

synapse/rest/consent/consent_resource.py

@@ -24,7 +24,7 @@
 from synapse.api.errors import NotFoundError, StoreError, SynapseError
 from synapse.config import ConfigError
 from synapse.http.server import DirectServeHtmlResource, respond_with_html
-from synapse.http.servlet import parse_string
+from synapse.http.servlet import parse_bytes, parse_string
 from synapse.types import UserID
 
 # language to use for the templates. TODO: figure this out from Accept-Language
@@ -116,7 +116,7 @@ async def _async_render_GET(self, request):
         has_consented = False
         public_version = username == ""
         if not public_version:
-            userhmac_bytes = parse_string(request, "h", required=True, encoding=None)
+            userhmac_bytes = parse_bytes(request, "h", required=True)
 
             self._check_hash(username, userhmac_bytes)
 
@@ -152,7 +152,7 @@ async def _async_render_POST(self, request):
         """
         version = parse_string(request, "v", required=True)
         username = parse_string(request, "u", required=True)
-        userhmac = parse_string(request, "h", required=True, encoding=None)
+        userhmac = parse_bytes(request, "h", required=True)
 
         self._check_hash(username, userhmac)
 

synapse/rest/media/v1/upload_resource.py

@@ -14,13 +14,13 @@
 # limitations under the License.
 
 import logging
-from typing import IO, TYPE_CHECKING
+from typing import IO, TYPE_CHECKING, Optional
 
 from twisted.web.server import Request
 
 from synapse.api.errors import Codes, SynapseError
 from synapse.http.server import DirectServeJsonResource, respond_with_json
-from synapse.http.servlet import parse_string
+from synapse.http.servlet import parse_bytes
 from synapse.http.site import SynapseRequest
 from synapse.rest.media.v1.media_storage import SpamMediaException
 
@@ -61,10 +61,10 @@ async def _async_render_POST(self, request: SynapseRequest) -> None:
                 errcode=Codes.TOO_LARGE,
             )
 
-        upload_name = parse_string(request, b"filename", encoding=None)
-        if upload_name:
+        upload_name_bytes = parse_bytes(request, "filename")
+        if upload_name_bytes:
             try:
-                upload_name = upload_name.decode("utf8")
+                upload_name = upload_name_bytes.decode("utf8")  # type: Optional[str]
             except UnicodeDecodeError:
                 raise SynapseError(
                     msg="Invalid UTF-8 filename parameter: %r" % (upload_name), code=400