Make #[derive(Schema)] no-op when openapi is disabled

examples/futures.rs

@@ -18,7 +18,7 @@ async fn sleepy(seconds: Seconds) -> Result<impl rweb::Reply, Infallible> {
 }
 
 /// A newtype to enforce our maximum allowed seconds.
-#[cfg_attr(feature = "openapi", derive(Schema))]
+#[derive(Schema)]
 struct Seconds(u64);
 
 impl FromStr for Seconds {

macros/src/lib.rs

@@ -84,6 +84,9 @@ pub fn router(
 /// See documentation of Entity for details and examples.
 #[proc_macro_derive(Schema, attributes(schema))]
 pub fn derive_schema(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    if !cfg!(feature = "openapi") {
+        return "".parse().unwrap();
+    }
     let input = syn::parse::<syn::DeriveInput>(input).expect("failed to parse derive input");
     openapi::derive_schema(input).into()
 }

src/lib.rs

@@ -293,7 +293,7 @@
 //! }
 //!
 //!
-//! #[cfg_attr(feature = "openapi", derive(Schema))]
+//! #[derive(Schema)]
 //! struct User {
 //!    id: String,
 //! }

src/openapi/entity.rs

@@ -15,7 +15,9 @@ pub type Responses = BTreeMap<Cow<'static, str>, Response>;
 ///
 /// # `#[derive(Schema)]`
 ///
-/// It implements [Entity] for the struct or enum.
+/// It implements [Entity] for the struct or enum. Note that it's recommended to
+/// use `derive(Schema)` even when you are not using openapi, as it is noop when
+/// cargo feature openapi is disabled.
 ///
 /// ## Overriding description
 ///