aio-libs/aiohttp · error · ValueError

path should be started with / or be empty

Error message

path should be started with / or be empty

What it means

Error "path should be started with / or be empty" thrown in aio-libs/aiohttp.

Source

Thrown at aiohttp/web_urldispatcher.py:1105

            index_key = index_key.partition("{")[0].rpartition("/")[0]
        return index_key.rstrip("/") or "/"

    def index_resource(self, resource: AbstractResource) -> None:
        """Add a resource to the resource index."""
        resource_key = self._get_resource_index_key(resource)
        # There may be multiple resources for a canonical path
        # so we keep them in a list to ensure that registration
        # order is respected.
        self._resource_index.setdefault(resource_key, []).append(resource)

    def unindex_resource(self, resource: AbstractResource) -> None:
        """Remove a resource from the resource index."""
        resource_key = self._get_resource_index_key(resource)
        self._resource_index[resource_key].remove(resource)

    def add_resource(self, path: str, *, name: str | None = None) -> Resource:
        if path and not path.startswith("/"):
            raise ValueError("path should be started with / or be empty")
        # Reuse last added resource if path and name are the same
        if self._resources:
            resource = self._resources[-1]
            if resource.name == name and resource.raw_match(path):
                return cast(Resource, resource)
        if not ("{" in path or "}" in path or ROUTE_RE.search(path)):
            resource = PlainResource(path, name=name)
            self.register_resource(resource)
            return resource
        resource = DynamicResource(path, name=name)
        self.register_resource(resource)
        return resource

    def add_route(
        self,
        method: str,
        path: str,
        handler: Handler | type[AbstractView],

View on GitHub (pinned to c0ef574e29)

When it happens

Trigger: Thrown at aiohttp/web_urldispatcher.py:1105 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of aio-libs/aiohttp@c0ef574e29 (2026-08-04). Data as JSON: /data/errors/3d973522e53542fd.json. Report an issue: GitHub.