Use immutabledict instead of frozendict (#15113)

Additionally:

* Consistently use `freeze()` in test

---------

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
Co-authored-by: 6543 <6543@obermui.de>

changelog.d/15113.misc

@@ -0,0 +1 @@
+Use `immutabledict` instead of `frozendict`.

pyproject.toml

@@ -153,15 +153,13 @@ python = "^3.7.1"
 # ----------------------
 # we use the TYPE_CHECKER.redefine method added in jsonschema 3.0.0
 jsonschema = ">=3.0.0"
-# frozendict 2.1.2 is broken on Debian 10: https://github.com/Marco-Sulla/python-frozendict/issues/41
-# We cannot test our wheels against the 2.3.5 release in CI. Putting in an upper bound for this
-# because frozendict has been more trouble than it's worth; we would like to move to immutabledict.
-frozendict = ">=1,!=2.1.2,<2.3.5"
+# We choose 2.0 as a lower bound: the most recent backwards incompatible release.
+# It seems generally available, judging by https://pkgs.org/search/?q=immutabledict
+immutabledict = ">=2.0"
 # We require 2.1.0 or higher for type hints. Previous guard was >= 1.1.0
 unpaddedbase64 = ">=2.1.0"
-# We require 1.5.0 to work around an issue when running against the C implementation of
-# frozendict: https://github.com/matrix-org/python-canonicaljson/issues/36
-canonicaljson = "^1.5.0"
+# We require 2.0.0 for immutabledict support.
+canonicaljson = "^2.0.0"
 # we use the type definitions added in signedjson 1.1.
 signedjson = "^1.1.0"
 # validating SSL certs for IP addresses requires service_identity 18.1.

synapse/__init__.py

@@ -17,9 +17,9 @@
 """ This is an implementation of a Matrix homeserver.
 """
 
-import json
 import os
 import sys
+from typing import Any, Dict
 
 from synapse.util.rust import check_rust_lib_up_to_date
 from synapse.util.stringutils import strtobool
@@ -61,11 +61,20 @@
 except ImportError:
     pass
 
-# Use the standard library json implementation instead of simplejson.
+# Teach canonicaljson how to serialise immutabledicts.
 try:
-    from canonicaljson import set_json_library
-
-    set_json_library(json)
+    from canonicaljson import register_preserialisation_callback
+    from immutabledict import immutabledict
+
+    def _immutabledict_cb(d: immutabledict) -> Dict[str, Any]:
+        try:
+            return d._dict
+        except Exception:
+            # Paranoia: fall back to a `dict()` call, in case a future version of
+            # immutabledict removes `_dict` from the implementation.
+            return dict(d)
+
+    register_preserialisation_callback(immutabledict, _immutabledict_cb)
 except ImportError:
     pass
 

synapse/crypto/event_signing.py

@@ -51,7 +51,7 @@ def check_event_content_hash(
     # some malformed events lack a 'hashes'. Protect against it being missing
     # or a weird type by basically treating it the same as an unhashed event.
     hashes = event.get("hashes")
-    # nb it might be a frozendict or a dict
+    # nb it might be a immutabledict or a dict
     if not isinstance(hashes, collections.abc.Mapping):
         raise SynapseError(
             400, "Malformed 'hashes': %s" % (type(hashes),), Codes.UNAUTHORIZED

synapse/events/snapshot.py

@@ -15,7 +15,7 @@
 from typing import TYPE_CHECKING, List, Optional, Tuple
 
 import attr
-from frozendict import frozendict
+from immutabledict import immutabledict
 
 from synapse.appservice import ApplicationService
 from synapse.events import EventBase
@@ -489,4 +489,4 @@ def _decode_state_dict(
     if input is None:
         return None
 
-    return frozendict({(etype, state_key): v for etype, state_key, v in input})
+    return immutabledict({(etype, state_key): v for etype, state_key, v in input})