make content encoding non exhaustive

actix-http/CHANGES.md

@@ -18,6 +18,7 @@
 ### Fixed
 * Potential HTTP request smuggling vulnerabilities. [RUSTSEC-2021-0081](https://github.com/rustsec/advisory-db/pull/977)
 
+
 ## 3.0.0-beta.8 - 2021-06-26
 ### Changed
 * Change compression algorithm features flags. [#2250]

actix-http/src/encoding/decoder.rs

@@ -1,7 +1,6 @@
 //! Stream decoders.
 
 use std::{
-    convert::TryFrom,
     future::Future,
     io::{self, Write as _},
     pin::Pin,
@@ -81,7 +80,7 @@ where
         let encoding = headers
             .get(&CONTENT_ENCODING)
             .and_then(|val| val.to_str().ok())
-            .and_then(|x| ContentEncoding::try_from(x).ok())
+            .and_then(|x| x.parse().ok())
             .unwrap_or(ContentEncoding::Identity);
 
         Self::new(stream, encoding)

actix-http/src/header/shared/content_encoding.rs

@@ -1,5 +1,6 @@
-use std::{convert::TryFrom, error, fmt, str::FromStr};
+use std::{convert::TryFrom, str::FromStr};
 
+use derive_more::{Display, Error};
 use http::header::InvalidHeaderValue;
 
 use crate::{
@@ -11,19 +12,13 @@ use crate::{
 /// Error return when a content encoding is unknown.
 ///
 /// Example: 'compress'
-#[derive(Debug)]
+#[derive(Debug, Display, Error)]
+#[display(fmt = "unsupported content encoding")]
 pub struct ContentEncodingParseError;
 
-impl fmt::Display for ContentEncodingParseError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Unsupported content encoding")
-    }
-}
-
-impl error::Error for ContentEncodingParseError {}
-
 /// Represents a supported content encoding.
-#[derive(Copy, Clone, PartialEq, Debug)]
+#[derive(Debug, Clone, Copy, PartialEq)]
+#[non_exhaustive]
 pub enum ContentEncoding {
     /// Automatically select encoding based on encoding negotiation.
     Auto,