actix/actix-web · error · syn::Error

missing arguments for scope macro, expected: #[scope("/prefi

Error message

missing arguments for scope macro, expected: #[scope("/prefix")]

What it means

The `#[scope(...)]` macro requires a prefix argument. At actix-web-codegen/src/scope.rs:18-23, if the args token stream is empty the macro errors with the expected form `#[scope("/prefix")]`.

Source

Thrown at actix-web-codegen/src/scope.rs:19

use proc_macro::TokenStream;
use proc_macro2::{Span, TokenStream as TokenStream2};
use quote::{quote, ToTokens as _};

use crate::{
    input_and_compile_error,
    route::{MethodType, RouteArgs},
};

pub fn with_scope(args: TokenStream, input: TokenStream) -> TokenStream {
    match with_scope_inner(args, input.clone()) {
        Ok(stream) => stream,
        Err(err) => input_and_compile_error(input, err),
    }
}

fn with_scope_inner(args: TokenStream, input: TokenStream) -> syn::Result<TokenStream> {
    if args.is_empty() {
        return Err(syn::Error::new(
            Span::call_site(),
            "missing arguments for scope macro, expected: #[scope(\"/prefix\")]",
        ));
    }

    let scope_prefix = syn::parse::<syn::LitStr>(args.clone()).map_err(|err| {
        syn::Error::new(
            err.span(),
            "argument to scope macro is not a string literal, expected: #[scope(\"/prefix\")]",
        )
    })?;

    let scope_prefix_value = scope_prefix.value();

    if scope_prefix_value.ends_with('/') {
        // trailing slashes cause non-obvious problems
        // it's better to point them out to developers rather than

View on GitHub (pinned to 937960ca67)

Solutions

1. Provide a prefix string literal: `#[scope("/api")]`.
2. If you want no prefix, use an empty string `#[scope("")]` (but a non-empty prefix is the normal use).

Example fix

// before
#[scope]
mod api { ... }

// after
#[scope("/api")]
mod api { ... }

// Compile-time only. #[scope] requires a non-empty argument.
// Always write #[scope("/prefix")] with a string literal prefix.

When it happens

Trigger: Writing `#[scope]` with no parentheses, or `#[scope()]` with empty parens.

Common situations: Treating `scope` like a marker attribute that needs no args, or a typo deleting the prefix string.

Related errors

• invalid service definition, expected #[<method>("<path>")]
• Multiple paths specified! There should be only one.
• The #[route(..)] macro requires at least one `method` attrib
• The #[routes] macro requires at least one `#[<method>(..)]`
• argument to scope macro is not a string literal, expected: #

AI-assisted analysis of actix/actix-web@937960ca67 (2026-08-06). Data as JSON: /data/errors/27b2520309689958.json. Report an issue: GitHub.