Support both import names of PyPI package python-multipart. (#17932)

changelog.d/17932.misc

@@ -0,0 +1 @@
+Support new package name of PyPI package `python-multipart` 0.0.13 so that distro packagers do not need to work around name conflict with PyPI package `multipart`.

synapse/http/client.py

@@ -36,7 +36,6 @@ from typing import (
 )
 
 import attr
-import multipart
 import treq
 from canonicaljson import encode_canonical_json
 from netaddr import AddrFormatError, IPAddress, IPSet
@@ -93,6 +92,20 @@ from synapse.util.async_helpers import timeout_deferred
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
+# Support both import names for the `python-multipart` (PyPI) library,
+# which renamed its package name from `multipart` to `python_multipart`
+# in 0.0.13 (though supports the old import name for compatibility).
+# Note that the `multipart` package name conflicts with `multipart` (PyPI)
+# so we should prefer importing from `python_multipart` when possible.
+try:
+    from python_multipart import MultipartParser
+
+    if TYPE_CHECKING:
+        from python_multipart import multipart
+except ImportError:
+    from multipart import MultipartParser  # type: ignore[no-redef]
+
+
 logger = logging.getLogger(__name__)
 
 outgoing_requests_counter = Counter("synapse_http_client_requests", "", ["method"])
@@ -1039,7 +1052,7 @@ class _MultipartParserProtocol(protocol.Protocol):
         self.deferred = deferred
         self.boundary = boundary
         self.max_length = max_length
-        self.parser: Optional[multipart.MultipartParser] = None
+        self.parser: Optional[MultipartParser] = None
         self.multipart_response = MultipartResponse()
         self.has_redirect = False
         self.in_json = False
@@ -1097,12 +1110,12 @@ class _MultipartParserProtocol(protocol.Protocol):
                         self.deferred.errback()
                     self.file_length += end - start
 
-            callbacks: "multipart.multipart.MultipartCallbacks" = {
+            callbacks: "multipart.MultipartCallbacks" = {
                 "on_header_field": on_header_field,
                 "on_header_value": on_header_value,
                 "on_part_data": on_part_data,
             }
-            self.parser = multipart.MultipartParser(self.boundary, callbacks)
+            self.parser = MultipartParser(self.boundary, callbacks)
 
         self.total_length += len(incoming_data)
         if self.max_length is not None and self.total_length >= self.max_length: