Raise an error if the converter arguments cannot be parsed

This could happen for example with `min=0;max=500` as the `;` is not a
word character everything before it is ignored in the regex during the
finditer call. This then lefts the user confused as the `min=0;` was
silently ignored.

CHANGES.rst

@@ -12,6 +12,8 @@ Unreleased
 -   Fix response_wrapper type check in test client. :issue:`2831`
 -   Make the return type of ``MultiPartParser.parse`` more
     precise. :issue:`2840`
+-   Raise an error if converter arguments cannot be
+    parsed. :issue:`2822`
 
 Version 3.0.1
 -------------

src/werkzeug/routing/rules.py

@@ -67,6 +67,7 @@ class RulePart:
 _simple_rule_re = re.compile(r"<([^>]+)>")
 _converter_args_re = re.compile(
     r"""
+    \s*
     ((?P<name>\w+)\s*=\s*)?
     (?P<value>
         True|False|
@@ -112,8 +113,14 @@ def parse_converter_args(argstr: str) -> tuple[tuple[t.Any, ...], dict[str, t.An
     argstr += ","
     args = []
     kwargs = {}
+    position = 0
 
     for item in _converter_args_re.finditer(argstr):
+        if item.start() != position:
+            raise ValueError(
+                f"Cannot parse converter argument '{argstr[position:item.start()]}'"
+            )
+
         value = item.group("stringval")
         if value is None:
             value = item.group("value")
@@ -123,6 +130,7 @@ def parse_converter_args(argstr: str) -> tuple[tuple[t.Any, ...], dict[str, t.An
         else:
             name = item.group("name")
             kwargs[name] = value
+        position = item.end()
 
     return tuple(args), kwargs
 

tests/test_routing.py

@@ -1076,6 +1076,9 @@ def test_converter_parser():
     args, kwargs = r.parse_converter_args('"foo", "bar"')
     assert args == ("foo", "bar")
 
+    with pytest.raises(ValueError):
+        r.parse_converter_args("min=0;max=500")
+
 
 def test_alias_redirects():
     m = r.Map(