Support fetches with redirect (#76)

* Support fetches with redirect

* pub

src/fetch/collection_id.rs

@@ -40,9 +40,10 @@ where
     where
         <Kind as Collection>::Error: From<Error>,
     {
-        let json = fetch_object_http(&self.0, data).await?;
-        Kind::verify(&json, &self.0, data).await?;
-        Kind::from_json(json, owner, data).await
+        let res = fetch_object_http(&self.0, data).await?;
+        let redirect_url = &res.url;
+        Kind::verify(&res.object, redirect_url, data).await?;
+        Kind::from_json(res.object, owner, data).await
     }
 }
 

src/fetch/mod.rs

@@ -23,6 +23,14 @@ pub mod object_id;
 /// Resolves identifiers of the form `name@example.com`
 pub mod webfinger;
 
+/// Response from fetching a remote object
+pub struct FetchObjectResponse<Kind> {
+    /// The resolved object
+    pub object: Kind,
+    /// Contains the final URL (different from request URL in case of redirect)
+    pub url: Url,
+}
+
 /// Fetch a remote object over HTTP and convert to `Kind`.
 ///
 /// [crate::fetch::object_id::ObjectId::dereference] wraps this function to add caching and
@@ -38,7 +46,7 @@ pub mod webfinger;
 pub async fn fetch_object_http<T: Clone, Kind: DeserializeOwned>(
     url: &Url,
     data: &Data<T>,
-) -> Result<Kind, Error> {
+) -> Result<FetchObjectResponse<Kind>, Error> {
     fetch_object_http_with_accept(url, data, FEDERATION_CONTENT_TYPE).await
 }
 
@@ -48,7 +56,7 @@ async fn fetch_object_http_with_accept<T: Clone, Kind: DeserializeOwned>(
     url: &Url,
     data: &Data<T>,
     content_type: &str,
-) -> Result<Kind, Error> {
+) -> Result<FetchObjectResponse<Kind>, Error> {
     let config = &data.config;
     // dont fetch local objects this way
     debug_assert!(url.domain() != Some(&config.domain));
@@ -84,5 +92,9 @@ async fn fetch_object_http_with_accept<T: Clone, Kind: DeserializeOwned>(
         return Err(Error::ObjectDeleted);
     }
 
-    res.json_limited().await
+    let url = res.url().clone();
+    Ok(FetchObjectResponse {
+        object: res.json_limited().await?,
+        url,
+    })
 }

src/fetch/object_id.rs

@@ -156,10 +156,11 @@ where
             return Err(anyhow!("Fetched remote object {} which was deleted", self).into());
         }
 
-        let res2 = res?;
+        let res = res?;
+        let redirect_url = &res.url;
 
-        Kind::verify(&res2, self.inner(), data).await?;
-        Kind::from_json(res2, data).await
+        Kind::verify(&res.object, redirect_url, data).await?;
+        Kind::from_json(res.object, data).await
     }
 }
 

src/fetch/webfinger.rs

@@ -38,7 +38,8 @@ where
 
     let res: Webfinger =
         fetch_object_http_with_accept(&Url::parse(&fetch_url)?, data, "application/jrd+json")
-            .await?;
+            .await?
+            .object;
 
     debug_assert_eq!(res.subject, format!("acct:{identifier}"));
     let links: Vec<Url> = res