Refactor storing URL params in extensions (#833)

axum/src/extract/path/mod.rs

@@ -5,14 +5,13 @@ mod de;
 
 use crate::{
     extract::{rejection::*, FromRequest, RequestParts},
-    routing::{InvalidUtf8InPathParam, UrlParams},
+    routing::url_params::UrlParams,
 };
 use async_trait::async_trait;
 use axum_core::response::{IntoResponse, Response};
 use http::StatusCode;
 use serde::de::DeserializeOwned;
 use std::{
-    borrow::Cow,
     fmt,
     ops::{Deref, DerefMut},
 };
@@ -162,9 +161,9 @@ where
     type Rejection = PathRejection;
 
     async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
-        let params = match req.extensions_mut().get::<Option<UrlParams>>() {
+        let params = match req.extensions_mut().get::<UrlParams>() {
-            Some(Some(UrlParams(Ok(params)))) => Cow::Borrowed(params),
+            Some(UrlParams::Params(params)) => params,
-            Some(Some(UrlParams(Err(InvalidUtf8InPathParam { key })))) => {
+            Some(UrlParams::InvalidUtf8InPathParam { key }) => {
                 let err = PathDeserializationError {
                     kind: ErrorKind::InvalidUtf8InPathParam {
                         key: key.as_str().to_owned(),
@@ -173,7 +172,6 @@ where
                 let err = FailedToDeserializePathParams(err);
                 return Err(err.into());
             }
-            Some(None) => Cow::Owned(Vec::new()),
             None => {
                 return Err(MissingPathParams.into());
             }

axum/src/routing/mod.rs

@@ -6,7 +6,7 @@ use crate::{
     extract::connect_info::{Connected, IntoMakeServiceWithConnectInfo},
     response::{IntoResponse, Redirect, Response},
     routing::strip_prefix::StripPrefix,
-    util::{try_downcast, ByteStr, PercentDecodedByteStr},
+    util::try_downcast,
     BoxError,
 };
 use http::{Request, Uri};
@@ -31,6 +31,7 @@ mod method_routing;
 mod not_found;
 mod route;
 mod strip_prefix;
+pub(crate) mod url_params;
 
 #[cfg(test)]
 mod tests;
@@ -446,14 +447,7 @@ where
             panic!("should always have a matched path for a route id");
         }
 
-        let params = match_
+        url_params::insert_url_params(req.extensions_mut(), match_.params);
-            .params
-            .iter()
-            .filter(|(key, _)| !key.starts_with(NEST_TAIL_PARAM))
-            .map(|(key, value)| (key.to_owned(), value.to_owned()))
-            .collect::<Vec<_>>();
-
-        insert_url_params(&mut req, params);
 
         let mut route = self
             .routes
@@ -557,49 +551,6 @@ fn with_path(uri: &Uri, new_path: &str) -> Uri {
     Uri::from_parts(parts).unwrap()
 }
 
-// we store the potential error here such that users can handle invalid path
-// params using `Result<Path<T>, _>`. That wouldn't be possible if we
-// returned an error immediately when decoding the param
-pub(crate) struct UrlParams(
-    pub(crate) Result<Vec<(ByteStr, PercentDecodedByteStr)>, InvalidUtf8InPathParam>,
-);
-
-fn insert_url_params<B>(req: &mut Request<B>, params: Vec<(String, String)>) {
-    let params = params
-        .into_iter()
-        .map(|(k, v)| {
-            if let Some(decoded) = PercentDecodedByteStr::new(v) {
-                Ok((ByteStr::new(k), decoded))
-            } else {
-                Err(InvalidUtf8InPathParam {
-                    key: ByteStr::new(k),
-                })
-            }
-        })
-        .collect::<Result<Vec<_>, _>>();
-
-    if let Some(current) = req.extensions_mut().get_mut::<Option<UrlParams>>() {
-        match params {
-            Ok(params) => {
-                let mut current = current.take().unwrap();
-                if let Ok(current) = &mut current.0 {
-                    current.extend(params);
-                }
-                req.extensions_mut().insert(Some(current));
-            }
-            Err(err) => {
-                req.extensions_mut().insert(Some(UrlParams(Err(err))));
-            }
-        }
-    } else {
-        req.extensions_mut().insert(Some(UrlParams(params)));
-    }
-}
-
-pub(crate) struct InvalidUtf8InPathParam {
-    pub(crate) key: ByteStr,
-}
-
 /// Wrapper around `matchit::Node` that supports merging two `Node`s.
 #[derive(Clone, Default)]
 struct Node {

axum/src/routing/url_params.rs

@@ -0,0 +1,45 @@
+use crate::util::{ByteStr, PercentDecodedByteStr};
+use http::Extensions;
+use matchit::Params;
+
+pub(crate) enum UrlParams {
+    Params(Vec<(ByteStr, PercentDecodedByteStr)>),
+    InvalidUtf8InPathParam { key: ByteStr },
+}
+
+pub(super) fn insert_url_params(extensions: &mut Extensions, params: Params) {
+    let current_params = extensions.get_mut();
+
+    if let Some(UrlParams::InvalidUtf8InPathParam { .. }) = current_params {
+        // nothing to do here since an error was stored earlier
+        return;
+    }
+
+    let params = params
+        .iter()
+        .filter(|(key, _)| !key.starts_with(super::NEST_TAIL_PARAM))
+        .map(|(key, value)| (key.to_owned(), value.to_owned()))
+        .map(|(k, v)| {
+            if let Some(decoded) = PercentDecodedByteStr::new(v) {
+                Ok((ByteStr::new(k), decoded))
+            } else {
+                Err(ByteStr::new(k))
+            }
+        })
+        .collect::<Result<Vec<_>, _>>();
+
+    match (current_params, params) {
+        (Some(UrlParams::InvalidUtf8InPathParam { .. }), _) => {
+            unreachable!("we check for this state earlier in this method")
+        }
+        (_, Err(invalid_key)) => {
+            extensions.insert(UrlParams::InvalidUtf8InPathParam { key: invalid_key });
+        }
+        (Some(UrlParams::Params(current)), Ok(params)) => {
+            current.extend(params);
+        }
+        (None, Ok(params)) => {
+            extensions.insert(UrlParams::Params(params));
+        }
+    }
+}