error on missing methods

actix-web-codegen/src/route.rs

@@ -427,7 +427,8 @@ pub(crate) fn with_methods(input: TokenStream) -> TokenStream {
 
     ast.attrs = others.into_iter().map(Result::unwrap_err).collect();
 
-    let methods = match methods
+    let methods =
+        match methods
             .into_iter()
             .map(Result::unwrap)
             .map(|(method, attr)| {
@@ -439,8 +440,15 @@ pub(crate) fn with_methods(input: TokenStream) -> TokenStream {
                     }
                 })
             })
-        .collect()
+            .collect::<Result<Vec<_>, _>>()
         {
+            Ok(methods) if methods.is_empty() => return input_and_compile_error(
+                input,
+                syn::Error::new(
+                    Span::call_site(),
+                    "The #[routes] macro requires at least one `#[<method>(..)]` attribute.",
+                ),
+            ),
             Ok(methods) => methods,
             Err(err) => return input_and_compile_error(input, err),
         };

actix-web-codegen/tests/trybuild.rs

@@ -13,6 +13,7 @@ fn compile_macros() {
     t.compile_fail("tests/trybuild/route-malformed-path-fail.rs");
 
     t.pass("tests/trybuild/routes-ok.rs");
+    t.compile_fail("tests/trybuild/routes-missing-method-fail.rs");
 
     t.pass("tests/trybuild/docstring-ok.rs");
 

actix-web-codegen/tests/trybuild/routes-missing-method-fail.rs

@@ -0,0 +1,13 @@
+use actix_web_codegen::*;
+
+#[routes]
+async fn index() -> String {
+    "Hello World!".to_owned()
+}
+
+#[actix_web::main]
+async fn main() {
+    use actix_web::App;
+
+    let srv = actix_test::start(|| App::new().service(index));
+}

actix-web-codegen/tests/trybuild/routes-missing-method-fail.stderr

@@ -0,0 +1,13 @@
+error: The #[routes] macro requires at least one `#[<method>(..)]` attribute.
+ --> tests/trybuild/routes-missing-method-fail.rs:3:1
+  |
+3 | #[routes]
+  | ^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `routes` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `fn() -> impl std::future::Future {index}: HttpServiceFactory` is not satisfied
+  --> tests/trybuild/routes-missing-method-fail.rs:12:55
+   |
+12 |     let srv = actix_test::start(|| App::new().service(index));
+   |                                                       ^^^^^ the trait `HttpServiceFactory` is not implemented for `fn() -> impl std::future::Future {index}`