sentry-tower: Use MatchedPath for transaction names (#570)

If the `axum-matched-path` feature of `sentry-tower` is used, it will enable the corresponding `matched-path` feature of `axum` and use the `MatchedPath` request extension to generate the transaction name. As before, the HTTP method is also still included in the transaction name.

sentry-tower/Cargo.toml

@@ -14,8 +14,10 @@ rust-version = "1.66"
 
 [features]
 http = ["dep:http", "pin-project", "url"]
+axum-matched-path = ["axum/matched-path"]
 
 [dependencies]
+axum = { version = "0.6", optional = true }
 tower-layer = "0.3"
 tower-service = "0.3"
 http = { version = "0.2.6", optional = true }

sentry-tower/src/http.rs

@@ -154,7 +154,7 @@ where
             let headers = request.headers().into_iter().flat_map(|(header, value)| {
                 value.to_str().ok().map(|value| (header.as_str(), value))
             });
-            let tx_name = format!("{} {}", request.method(), request.uri().path());
+            let tx_name = format!("{} {}", request.method(), path_from_request(&request));
             Some(sentry_core::TransactionContext::continue_from_headers(
                 &tx_name,
                 "http.server",
@@ -172,6 +172,15 @@ where
     }
 }
 
+fn path_from_request<B>(request: &Request<B>) -> &str {
+    #[cfg(feature = "axum-matched-path")]
+    if let Some(matched_path) = request.extensions().get::<axum::extract::MatchedPath>() {
+        return matched_path.as_str();
+    }
+
+    request.uri().path()
+}
+
 fn map_status(status: StatusCode) -> protocol::SpanStatus {
     match status {
         StatusCode::UNAUTHORIZED => protocol::SpanStatus::Unauthenticated,