Backport changes from main to v0.6.x (#2141)

Co-authored-by: David Pedersen <[email protected]>

axum-extra/src/response/erased_json.rs

@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use axum::{
     http::{header, HeaderValue, StatusCode},
     response::{IntoResponse, Response},
@@ -29,21 +31,29 @@ use serde::Serialize;
 /// }
 /// ```
 #[cfg_attr(docsrs, doc(cfg(feature = "erased-json")))]
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 #[must_use]
-pub struct ErasedJson(serde_json::Result<Bytes>);
+pub struct ErasedJson(Result<Bytes, Arc<serde_json::Error>>);
 
 impl ErasedJson {
     /// Create an `ErasedJson` by serializing a value with the compact formatter.
     pub fn new<T: Serialize>(val: T) -> Self {
         let mut bytes = BytesMut::with_capacity(128);
-        Self(serde_json::to_writer((&mut bytes).writer(), &val).map(|_| bytes.freeze()))
+        let result = match serde_json::to_writer((&mut bytes).writer(), &val) {
+            Ok(()) => Ok(bytes.freeze()),
+            Err(e) => Err(Arc::new(e)),
+        };
+        Self(result)
     }
 
     /// Create an `ErasedJson` by serializing a value with the pretty formatter.
     pub fn pretty<T: Serialize>(val: T) -> Self {
         let mut bytes = BytesMut::with_capacity(128);
-        Self(serde_json::to_writer_pretty((&mut bytes).writer(), &val).map(|_| bytes.freeze()))
+        let result = match serde_json::to_writer_pretty((&mut bytes).writer(), &val) {
+            Ok(()) => Ok(bytes.freeze()),
+            Err(e) => Err(Arc::new(e)),
+        };
+        Self(result)
     }
 }