feat: add &mut versions of as_response_error/as_error/HttpResponse::e…

actix-web/src/error/error.rs

@@ -17,16 +17,26 @@ pub struct Error {
 }
 
 impl Error {
-    /// Returns the reference to the underlying `ResponseError`.
+    /// Returns a reference to the underlying `ResponseError`.
     pub fn as_response_error(&self) -> &dyn ResponseError {
         self.cause.as_ref()
     }
 
+    /// Returns a mutable reference to the underlying `ResponseError`.
+    pub fn as_response_error_mut(&mut self) -> &mut dyn ResponseError {
+        self.cause.as_mut()
+    }
+
     /// Similar to `as_response_error` but downcasts.
     pub fn as_error<T: ResponseError + 'static>(&self) -> Option<&T> {
         <dyn ResponseError>::downcast_ref(self.cause.as_ref())
     }
 
+    /// Similar to `as_response_error_mut` but downcasts.
+    pub fn as_error_mut<T: ResponseError + 'static>(&mut self) -> Option<&mut T> {
+        <dyn ResponseError>::downcast_mut(self.cause.as_mut())
+    }
+
     /// Shortcut for creating an `HttpResponse`.
     pub fn error_response(&self) -> HttpResponse {
         self.cause.error_response()

actix-web/src/response/response.rs

@@ -73,12 +73,18 @@ impl<B> HttpResponse<B> {
         self.res.head_mut()
     }
 
-    /// The source `error` for this response
+    /// Returns a reference to the source `error` for this response.
     #[inline]
     pub fn error(&self) -> Option<&Error> {
         self.error.as_ref()
     }
 
+    /// Returns a mutable reference to the source `error` for this response.
+    #[inline]
+    pub fn error_mut(&mut self) -> Option<&mut Error> {
+        self.error.as_mut()
+    }
+
     /// Get the response status code
     #[inline]
     pub fn status(&self) -> StatusCode {