Add a check for overlapping paths.

synapse/http/server.py

@@ -459,6 +459,47 @@ def register_paths(
                 callback, servlet_classname
             )
 
+    def check_paths(self):
+        import re
+
+        with open('conflicts.txt', "a") as f:
+
+            for path_pattern in self._routes.keys():
+                # Push rules have weird routing.
+                if "pushrules/" in path_pattern.pattern:
+                    continue
+
+                # Try to find conflicts.
+                needle = path_pattern.pattern.lstrip("^").rstrip("$")
+                for group_name in path_pattern.groupindex.keys():
+                    value = group_name
+                    if group_name == "membership_action":
+                        value = "join"
+                    needle = re.sub(fr"\(\?P<{group_name}>[^)]+\)", value, needle)
+                    needle = needle.replace("\\", "")
+
+                # There should only be a single group left to match the version.
+                def get_ver(m):
+                    return m.group().lstrip("(").rstrip(")").split("|")[0]
+                needle = re.sub(r"\([^)]+?\)", get_ver, needle)
+
+                # The needle must match itself.
+                assert path_pattern.match(needle) is not None, f"{needle} does not match {path_pattern.pattern}"
+
+                # See if the new fake-ish path matches any previous registered paths.
+                matches = []
+                for p in self._routes.keys():
+                    # Skip yourself.
+                    if p is path_pattern:
+                        continue
+
+                    m = p.match(needle)
+                    if m:
+                        matches.append(p.pattern)
+
+                if matches:
+                    f.write(f"Conflicting paths: {path_pattern.pattern}: {matches}\n")
+
     def _get_handler_for_request(
         self, request: SynapseRequest
     ) -> Tuple[ServletCallback, str, Dict[str, str]]:

synapse/rest/__init__.py

@@ -151,3 +151,5 @@ def register_servlets(client_resource: HttpServer, hs: "HomeServer") -> None:
             mutual_rooms.register_servlets(hs, client_resource)
             login_token_request.register_servlets(hs, client_resource)
             rendezvous.register_servlets(hs, client_resource)
+
+        client_resource.check_paths()

synapse/rest/client/_base.py

@@ -43,19 +43,15 @@ def client_patterns(
     Returns:
         An iterable of patterns.
     """
-    patterns = []
+    prefixes = []
 
     if unstable:
-        unstable_prefix = CLIENT_API_PREFIX + "/unstable"
-        patterns.append(re.compile("^" + unstable_prefix + path_regex))
+        prefixes.append("unstable")
     if v1:
-        v1_prefix = CLIENT_API_PREFIX + "/api/v1"
-        patterns.append(re.compile("^" + v1_prefix + path_regex))
-    for release in releases:
-        new_prefix = CLIENT_API_PREFIX + f"/{release}"
-        patterns.append(re.compile("^" + new_prefix + path_regex))
+        prefixes.append("api/v1")
+    prefixes.extend(releases)
 
-    return patterns
+    return [re.compile("^" + CLIENT_API_PREFIX + "/(" + "|".join(prefixes) + ")" + path_regex)]
 
 
 def set_timeline_upper_limit(filter_json: JsonDict, filter_timeline_limit: int) -> None: