fix: improve source error message (#138)

Previously, if an endpoint failed to fetch the source, the endpoint
would respond with a status 500 and an error message too specific. For
example, it could be a "500: bad url" which is not very clear to the
user that it's the source url that's broken or an url elsewhere.

This commit improves on the error message by providing a more
user-friendly message:

- http request errors from anywhere in the pipeline will show as a 502
error with the failed status code and the requesting url is returned in
the error message
- source errors will indicate it's a source error

src/server/endpoint.rs

@@ -11,7 +11,6 @@ use axum::response::IntoResponse;
 use axum::RequestExt;
 use http::header::HOST;
 use http::request::Parts;
-use http::StatusCode;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use tokio::sync::Mutex;
@@ -207,9 +206,10 @@ impl EndpointService {
   async fn handle(self, mut req: Request) -> Result<Response, Response> {
     // infallible
     let param: EndpointParam = req.extract_parts().await.unwrap();
-    let feed = self.run(param).await.map_err(|e| {
-      (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()).into_response()
-    })?;
+    let feed = self
+      .run(param)
+      .await
+      .map_err(|e| e.into_http().into_response())?;
     let resp = feed.into_response();
     Ok(resp)
   }
@@ -242,7 +242,8 @@ impl EndpointService {
     let source = self.find_source(&param.source)?;
     let feed = source
       .fetch_feed(Some(&self.client), param.base.as_ref())
-      .await?;
+      .await
+      .map_err(|e| Error::FetchSource(Box::new(e)))?;
     let mut context = FilterContext::new();
     if let Some(limit_filters) = param.limit_filters {
       context.set_limit_filters(limit_filters);

src/util.rs

@@ -1,3 +1,4 @@
+use http::StatusCode;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use url::Url;
@@ -118,10 +119,29 @@ pub enum Error {
   #[error("Unsupported feed format: {0}")]
   UnsupportedFeedFormat(String),
 
+  #[error("Failed fetching source: {0}")]
+  FetchSource(Box<Error>),
+
   #[error("{0}")]
   Message(String),
 }
 
+impl Error {
+  pub fn into_http(self) -> (StatusCode, String) {
+    match self {
+      Error::FetchSource(e) => {
+        let (status, body) = e.into_http();
+        (status, format!("Error fetching source: {body}"))
+      }
+      Error::HttpStatus(status, url) => {
+        let body = format!("Error requesting {url}: {status}");
+        (StatusCode::BAD_GATEWAY, body)
+      }
+      _ => (StatusCode::INTERNAL_SERVER_ERROR, format!("{self}")),
+    }
+  }
+}
+
 #[derive(
   JsonSchema, Serialize, Deserialize, Clone, Debug, PartialEq, Eq, Hash,
 )]