feat: Add support for default

Author: bahlo

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Implement `std::error::Error` for `AcceptRejection`
+- Add support for `Default`
 
 ## [0.0.3] - 2025-07-08
 

axum-accept-macros/src/lib.rs

@@ -59,6 +59,13 @@ pub fn derive_accept_extractor(input: TokenStream) -> TokenStream {
         panic!("AcceptExtractor can only be derived for enums");
     };
 
+    let has_default = data.variants.iter().any(|variant| {
+        variant.attrs.iter().any(|attr| match &attr.meta {
+            Meta::Path(path) => path.is_ident("default"),
+            _ => false,
+        })
+    });
+
     let mut match_arms = Vec::new();
 
     for variant in &data.variants {
@@ -90,12 +97,24 @@ pub fn derive_accept_extractor(input: TokenStream) -> TokenStream {
         }
     }
 
+    let check_and_return_default = if has_default {
+        Some(quote! {
+            if mediatypes.is_empty() {
+                return Ok(#name::default());
+            }
+        })
+    } else {
+        None
+    };
+
     let expanded = quote! {
         impl #impl_generics axum::extract::FromRequestParts<S> for #name #ty_generics #where_clause {
             type Rejection = axum_accept::AcceptRejection;
 
             async fn from_request_parts(parts: &mut axum::http::request::Parts, _state: &S) -> Result<Self, Self::Rejection> {
-                for mt in axum_accept::parse_mediatypes(&parts.headers)? {
+                let mediatypes = axum_accept::parse_mediatypes(&parts.headers)?;
+                #check_and_return_default
+                for mt in mediatypes {
                     match (mt.ty.as_str(), mt.subty.as_str(), mt.suffix.map(|s| s.as_str())) {
                         #(#match_arms)*
                         _ => {} // continue searching

axum-accept/src/lib.rs

@@ -117,4 +117,33 @@ mod tests {
         };
         Ok(())
     }
+
+    #[derive(Debug, AcceptExtractor, Default)]
+    enum AcceptWithDefault {
+        #[default]
+        #[accept(mediatype = "text/plain")]
+        TextPlain,
+        #[accept(mediatype = "application/json")]
+        ApplicationJson,
+    }
+
+    #[tokio::test]
+    async fn test_accept_extractor_default() -> Result<(), Box<dyn std::error::Error>> {
+        let req = Request::builder()
+            .header("accept", "text/csv")
+            .body(Body::from(""))?;
+        let state = ();
+        let media_type = AcceptWithDefault::from_request(req, &state).await;
+        let Err(AcceptRejection::NoSupportedMediaTypeFound) = media_type else {
+            panic!("expected no supported media type found")
+        };
+
+        let req = Request::builder().body(Body::from(""))?;
+        let state = ();
+        let media_type = AcceptWithDefault::from_request(req, &state).await;
+        let Ok(AcceptWithDefault::TextPlain) = media_type else {
+            panic!("expected text/plain (default)")
+        };
+        Ok(())
+    }
 }