Bugfix the calculation of weighting based on static parts

Only static parts that are more than a `/` should count towards the
weighting, as they influence the part for matching. This prevents
`/<path:p>/<a>/<b>` matching before `/<path:p>/b` as only the latter
rule should have a static weighting as it is the only rule that has a
static part.

CHANGES.rst

@@ -9,6 +9,8 @@ Unreleased
     slashes mode is disabled for the rule. :issue:`2467`
 -   Fix router so that partial part matches are not allowed
     i.e. ``/2df`` does not match ``/<int>``. :pr:`2470`
+-   Fix router static part weighting, so that simpler routes are matched
+    before more complex ones. :issue:`2471`
 -   Restore ``ValidationError`` to be importable from
     ``werkzeug.routing``. :issue:`2465`
 

src/werkzeug/routing/rules.py

@@ -592,8 +592,12 @@ def _parse_rule(self, rule: str) -> t.Iterable[RulePart]:
 
             data = match.groupdict()
             if data["static"]:
-                static_weights.append((static_parts, -len(data["static"])))
-                static_parts += 1
+                # Only static parts beyond the `/` count towards the
+                # weighting (more static parts mean the rule should be
+                # weighted first).
+                if data["static"] != "/":
+                    static_weights.append((static_parts, -len(data["static"])))
+                    static_parts += 1
                 self._trace.append((False, data["static"]))
 
             if data["variable"] is not None:

tests/test_routing.py

@@ -1394,6 +1394,18 @@ def test_rule_websocket_methods():
     r.Rule("/ws", endpoint="ws", websocket=True, methods=["get", "head", "options"])
 
 
+def test_path_weighting():
+    m = r.Map(
+        [
+            r.Rule("/<path:path>/c", endpoint="simple"),
+            r.Rule("/<path:path>/<a>/<b>", endpoint="complex"),
+        ]
+    )
+    a = m.bind("localhost", path_info="/a/b/c")
+
+    assert a.match() == ("simple", {"path": "a/b"})
+
+
 def test_newline_match():
     m = r.Map([r.Rule("/hello", endpoint="hello")])
     a = m.bind("localhost")