Add a DuplicatedRulesError

This is raised if an equivalent rule is added to the matcher to an
existing rule. This should help users of the router know when they've
accidentally duplicated a match.

Author: pgjones

src/werkzeug/routing/exceptions.py

@@ -17,6 +17,11 @@
     from .rules import Rule
 
 
+class DuplicatedRulesError(Exception):
+    def __init__(self, rules: list[Rule]) -> None:
+        self.rules = rules
+
+
 class RoutingException(Exception):
     """Special exceptions that require the application to redirect, notifying
     about missing urls, etc.

src/werkzeug/routing/matcher.py

@@ -6,6 +6,7 @@
 from dataclasses import field
 
 from .converters import ValidationError
+from .exceptions import DuplicatedRulesError
 from .exceptions import NoMatch
 from .exceptions import RequestAliasRedirect
 from .exceptions import RequestPath
@@ -50,6 +51,11 @@ def add(self, rule: Rule) -> None:
                     new_state = State()
                     state.dynamic.append((part, new_state))
                     state = new_state
+
+        for existing in state.rules:
+            if rule == existing:
+                raise DuplicatedRulesError([rule, existing])
+
         state.rules.append(rule)
 
     def update(self) -> None:

src/werkzeug/routing/rules.py

@@ -907,7 +907,11 @@ def build_compare_key(self) -> tuple[int, int, int]:
         return (1 if self.alias else 0, -len(self.arguments), -len(self.defaults or ()))
 
     def __eq__(self, other: object) -> bool:
-        return isinstance(other, type(self)) and self._trace == other._trace
+        return (
+            isinstance(other, type(self))
+            and self._parts == other._parts
+            and self.websocket == other.websocket
+        )
 
     __hash__ = None  # type: ignore
 

tests/test_routing.py

@@ -9,6 +9,7 @@
 from werkzeug.datastructures import MultiDict
 from werkzeug.exceptions import MethodNotAllowed
 from werkzeug.exceptions import NotFound
+from werkzeug.routing.exceptions import DuplicatedRulesError
 from werkzeug.test import create_environ
 from werkzeug.wrappers import Response
 
@@ -246,6 +247,30 @@ def test_strict_slashes_leaves_dont_consume():
     assert adapter.match("/path5/", method="GET") == ("leaf", {})
 
 
+def test_duplicated_matches():
+    r.Map(
+        [
+            r.Rule("/", endpoint="leaf"),
+            r.Rule("/", endpoint="websocket", websocket=True),
+            r.Rule("/", endpoint="subdomain", subdomain="abc"),
+        ]
+    )
+    with pytest.raises(DuplicatedRulesError):
+        r.Map(
+            [
+                r.Rule("/", endpoint="leaf"),
+                r.Rule("/", endpoint="branch"),
+            ]
+        )
+    with pytest.raises(DuplicatedRulesError):
+        r.Map(
+            [
+                r.Rule("/<foo>", endpoint="leaf"),
+                r.Rule("/<bar>", endpoint="branch"),
+            ]
+        )
+
+
 def test_environ_defaults():
     environ = create_environ("/foo")
     assert environ["PATH_INFO"] == "/foo"