tweak error pattern

src/error.rs

@@ -1,4 +1,5 @@
 //! Error and Result module
+
 pub use actix_http::error::*;
 use derive_more::{Display, From};
 use serde_json::error::Error as JsonError;

src/lib.rs

@@ -106,7 +106,7 @@ pub use crate::responder::Responder;
 pub use crate::route::Route;
 pub use crate::scope::Scope;
 pub use crate::server::HttpServer;
-pub use crate::types::Either;
+pub use crate::types::{Either, EitherExtractError};
 
 pub mod dev {
     //! The `actix-web` prelude for library developers

src/types/either.rs

@@ -108,16 +108,17 @@ where
     }
 }
 
+/// A composite error resulting from failure to extract an `Either<A, B>`.
+///
+/// The implementation of `Into<actix_web::Error>` will return the payload buffering error or the
+/// error from the primary extractor. To access the fallback error, use a match clause.
 #[derive(Debug)]
 pub enum EitherExtractError<A, B> {
     /// Error from payload buffering, such as exceeding payload max size limit.
     Bytes(Error),
 
     /// Error from primary extractor.
-    A(A),
+    Extract(A, B),
-
-    /// Error from fallback extractor.
-    B(B),
 }
 
 impl<A, B> Into<Error> for EitherExtractError<A, B>
@@ -128,8 +129,7 @@ where
     fn into(self) -> Error {
         match self {
             EitherExtractError::Bytes(err) => err,
-            EitherExtractError::A(err) => err.into(),
+            EitherExtractError::Extract(a_err, _b_err) => a_err.into(),
-            EitherExtractError::B(err) => err.into(),
         }
     }
 }
@@ -179,7 +179,7 @@ where
     let mut pl = payload_from_bytes(fallback);
     match B::from_request(&req, &mut pl).await {
         Ok(b_data) => return Ok(Either::B(b_data)),
-        Err(_b_err) => Err(EitherExtractError::A(a_err)),
+        Err(b_err) => Err(EitherExtractError::Extract(a_err, b_err)),
     }
 }
 
@@ -251,4 +251,24 @@ mod tests {
             .unwrap_right();
         assert_eq!(&payload.as_ref(), &b"!@$%^&*()");
     }
+
+    #[actix_rt::test]
+    async fn test_either_extract_recursive_fallback_inner() {
+        let (req, mut pl) = TestRequest::default()
+            .set_json(&TestForm {
+                hello: "world".to_owned(),
+            })
+            .to_http_parts();
+
+        let form =
+            Either::<Either<Form<TestForm>, Json<TestForm>>, Bytes>::from_request(
+                &req, &mut pl,
+            )
+            .await
+            .unwrap()
+            .unwrap_left()
+            .unwrap_right()
+            .into_inner();
+        assert_eq!(&form.hello, "world");
+    }
 }

src/types/mod.rs

@@ -8,7 +8,7 @@ pub(crate) mod payload;
 mod query;
 pub(crate) mod readlines;
 
-pub use self::either::Either;
+pub use self::either::{Either, EitherExtractError};
 pub use self::form::{Form, FormConfig};
 pub use self::json::{Json, JsonConfig};
 pub use self::path::{Path, PathConfig};