DioxusLabs/dioxus · error · syn::Error

expected path to start with '/'

Error message

expected path to start with '/'

What it means

RouteParser::new requires the path portion of the route literal to start with `/` (packages/fullstack-macro/src/lib.rs:985-988). Without a leading slash the generated axum route would be relative/invalid, so the macro refuses it immediately.

Source

Thrown at packages/fullstack-macro/src/lib.rs:986

}

struct RouteParser {
    path_params: Vec<(Slash, PathParam)>,
    query_params: Vec<QueryParam>,
}

impl RouteParser {
    fn new(lit: LitStr) -> syn::Result<Self> {
        let val = lit.value();
        let span = lit.span();
        let split_route = val.split('?').collect::<Vec<_>>();
        if split_route.len() > 2 {
            return Err(syn::Error::new(span, "expected at most one '?'"));
        }

        let path = split_route[0];
        if !path.starts_with('/') {
            return Err(syn::Error::new(span, "expected path to start with '/'"));
        }
        let path = path.strip_prefix('/').unwrap();

        let mut path_params = Vec::new();

        for path_param in path.split('/') {
            path_params.push((
                Slash(span),
                PathParam::new(path_param, span, Box::new(parse_quote!(())))?,
            ));
        }

        let path_param_len = path_params.len();
        for (i, (_slash, path_param)) in path_params.iter().enumerate() {
            match path_param {
                PathParam::WildCard(_, _, _, _, _, _) => {
                    if i != path_param_len - 1 {
                        return Err(syn::Error::new(

View on GitHub (pinned to 393d190a80)

Solutions

1. Add the leading slash: `#[route(GET, "/items/{id}")]`.
2. Double-check any route constants shared between client and server — the server macro always requires the slash.
3. If the intent was a client-side page route, use dioxus-router's route macro instead of the fullstack one.

Example fix

// before
#[route(GET, "items/{id}")]
async fn item(id: i32) { ... }

// after
#[route(GET, "/items/{id}")]
async fn item(id: i32) { ... }

fn validate_route(route: &str) -> Result<(), String> {
    let path = route.split('?').next().unwrap();
    if !path.starts_with('/') {
        return Err(format!("path must start with '/': {route}"));
    }
    Ok(())
}

When it happens

Trigger: `#[route(GET, "items/{id}")]`; `#[get("home")]`; building the string with `format!`-like composition in source and dropping the slash; porting a frontend Dioxus router route (which does not need a leading slash in some contexts) into a fullstack route attribute.

Common situations: Confusion between client-side `#[route]` (dioxus-router) and server-side fullstack `#[route]` conventions; typos; trimming slashes during copy-paste.

Related errors

• Use `api_route` instead of `route` to use OpenAPI options
• path parameter `{}` not found in function arguments
• query parameter `{}` not found in function arguments
• Cannot have multiple query parameters when one is a catch-al
• HTTP method specified both in macro and in attribute

AI-assisted analysis of DioxusLabs/dioxus@393d190a80 (2026-08-16). Data as JSON: /api/errors/6b42c7da5e7a3c2e. Report an issue: GitHub.