refactor: Error instead of breaking

hook-worker/src/error.rs

@@ -47,6 +47,8 @@ pub enum WebhookResponseError {
     ParseUTF8StringError(#[from] std::str::Utf8Error),
     #[error("error while iterating over response body chunks")]
     StreamIterationError(#[from] reqwest::Error),
+    #[error("attempted to slice a chunk of length {0} with an out of bounds index of {1}")]
+    ChunkOutOfBoundsError(usize, usize),
 }
 
 /// Implement display of `WebhookRequestError` by appending to the underlying `reqwest::Error`

hook-worker/src/util.rs

@@ -17,13 +17,18 @@ pub async fn first_n_bytes_of_response(
 
         let chunk = chunk?;
         let chunk_str = std::str::from_utf8(&chunk)?;
-        if let Some(partial_chunk_str) =
-            chunk_str.get(0..std::cmp::min(n - buffer.len(), chunk_str.len()))
-        {
-            buffer.push_str(&partial_chunk_str);
+        let upper_bound = std::cmp::min(n - buffer.len(), chunk_str.len());
+
+        if let Some(partial_chunk_str) = chunk_str.get(0..upper_bound) {
+            buffer.push_str(partial_chunk_str);
         } else {
-            // For whatever reason, we are out of bounds, give up.
-            break;
+            // For whatever reason we are out of bounds. We should never land here
+            // given the `std::cmp::min` usage, but I am being extra careful by not
+            // using a slice index that would panic instead.
+            return Err(WebhookResponseError::ChunkOutOfBoundsError(
+                chunk_str.len(),
+                upper_bound,
+            ));
         }
     }