fix(transport): eagerly format itertools to prevent double-format panic#3668
Merged
fix(transport): eagerly format itertools to prevent double-format panic#3668
Conversation
`.format()` from itertools returns a `Format` struct that panics if displayed more than once. The `#[instrument]` macro may format span fields multiple times, causing a panic at runtime. Fixes #3666 Amp-Thread-ID: https://ampcode.com/threads/T-019c42f3-5cf9-75b1-81a1-cb2a6029a2db Co-authored-by: Amp <[email protected]>
gakonst
requested review from
DaniPopes,
grandizzy,
klkvr,
mattsse,
onbjerg and
zerosnacks
as code owners
mattsse
approved these changes
Feb 9, 2026
DaniPopes
approved these changes
Feb 9, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Fixes the panic introduced in f69665c when
#[instrument]formats the itertoolsFormatstruct more than once.Changes
.to_string()on.format(", ")in bothhyper_transport.rsandreqwest_transport.rsto eagerly evaluate the formatterContext
itertools::Formatpanics with "Format: was already formatted once" ifDisplayis called twice. The#[instrument]macro can format span fields multiple times, triggering this at runtime.Closes #3666