server/upload_path: Expose the final file size in the response

attic/src/api/v1/upload_path.rs

@@ -57,6 +57,10 @@ pub struct UploadPathNarInfo {
 pub struct UploadPathResult {
     #[serde_as(deserialize_as = "DefaultOnError")]
     pub kind: UploadPathResultKind,
+
+    /// The compressed size of the NAR, in bytes.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub file_size: Option<usize>,
 }
 
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]

server/src/api/v1/upload_path.rs

@@ -188,11 +188,16 @@ async fn upload_path_dedup(
 
     txn.commit().await.map_err(ServerError::database_error)?;
 
+    let file_size = existing_nar.file_size
+        .map(|dbs| dbs.try_into().map_err(ServerError::database_error))
+        .transpose()?;
+
     // Ensure it's not unlocked earlier
     drop(existing_nar);
 
     Ok(Json(UploadPathResult {
         kind: UploadPathResultKind::Deduplicated,
+        file_size,
     }))
 }
 
@@ -339,6 +344,7 @@ async fn upload_path_new(
 
     Ok(Json(UploadPathResult {
         kind: UploadPathResultKind::Uploaded,
+        file_size: Some(*file_size),
     }))
 }