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(draft) refactor(esplora): clear remaining panic paths #2053

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(draft) refactor(esplora): clear remaining panic paths #2053

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e35a862
fix(esplora): propagate thread join failures
reez Sep 29, 2025
7d67591
fix(esplora): error if keychain iteration yields no indices
reez Sep 29, 2025
481f92d
fix(esplora): replace .expect() with error handling in chain_update
reez Sep 22, 2025
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17 changes: 15 additions & 2 deletions crates/esplora/src/async_ext.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -264,7 +264,7 @@ async fn chain_update<S: Sleeper>(

tip = tip
.extend(conflicts.into_iter().rev().map(|b| (b.height, b.hash)))
.expect("evicted are in order");
.map_err(|_| Box::new(esplora_client::Error::InvalidResponse))?;

for (anchor, _txid) in anchors {
let height = anchor.block_id.height;
Expand Down Expand Up @@ -348,6 +348,9 @@ where
.collect::<FuturesOrdered<_>>();

if handles.is_empty() {
if last_index.is_none() {
return Err(Box::new(esplora_client::Error::InvalidResponse));
}
break;
}

Expand All @@ -368,7 +371,8 @@ where
.extend(evicted.into_iter().map(|txid| (txid, start_time)));
}

let last_index = last_index.expect("Must be set since handles wasn't empty.");
let last_index =
last_index.ok_or_else(|| Box::new(esplora_client::Error::InvalidResponse))?;
Comment on lines +374 to +375
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One suggestion is to leave last_index as an Option and wrap stop_gap in Some(..) when doing the comparison.

But there's a much better way to handle this, which is to introduce an unused_count variable. Now when processing handles, if txs.is_empty() we increment the unused count, else update the last active index (and reset the unused count). Finally, break once the unused count reaches the gap limit. AFAICT there'd be no reason to keep track of the last_index scanned.

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Took your suggestion and worked it in; didn't want to push it to this branch yet if I had the wrong idea, but here is the commit reez@35538e2 on a branch that builds on this branch.

I felt like I had to keep two small guardrails from the old logic:

  • processed_any (still surface the “no handles ran” error)
  • gap_limit = stop_gap.max(1)(keeps old “stop_gap==0 still means one empty derivation” behavior)

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I don't think it's an error if handles turns up empty - we need a way to break from the loop once all of the keychain-spks are consumed.

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Maybe stop_gap = stop_gap.max(parallel_requests), since we check at least 1 spk-index for every request in parallel_requests.

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Super helpful thanks mammal, I made the below changes to that my side branch esplora+mammal that I can eventually fold back into this esplora branch if I'm on the right track

I don't think it's an error if handles turns up empty - we need a way to break from the loop once all of the keychain-spks are consumed.

Good call. I made this change 36073d0 based on that

Maybe stop_gap = stop_gap.max(parallel_requests), since we check at least 1 spk-index for every request in parallel_requests.

Good catch, made another change 590edcf based on this

let gap_limit_reached = if let Some(i) = last_active_index {
last_index >= i.saturating_add(stop_gap as u32)
} else {
Expand Down Expand Up @@ -571,6 +575,15 @@ mod test {
}};
}

#[test]
fn ensure_last_index_none_returns_error() {
let last_index: Option<u32> = None;
let err = last_index
.ok_or_else(|| Box::new(esplora_client::Error::InvalidResponse))
.unwrap_err();
assert!(matches!(*err, esplora_client::Error::InvalidResponse));
}

// Test that `chain_update` fails due to wrong network.
#[tokio::test]
async fn test_chain_update_wrong_network_error() -> anyhow::Result<()> {
Expand Down
54 changes: 48 additions & 6 deletions crates/esplora/src/blocking_ext.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -249,7 +249,7 @@ fn chain_update(

tip = tip
.extend(conflicts.into_iter().rev().map(|b| (b.height, b.hash)))
.expect("evicted are in order");
.map_err(|_| Box::new(esplora_client::Error::InvalidResponse))?;

for (anchor, _) in anchors {
let height = anchor.block_id.height;
Expand Down Expand Up @@ -316,11 +316,17 @@ fn fetch_txs_with_keychain_spks<I: Iterator<Item = Indexed<SpkWithExpectedTxids>
.collect::<Vec<JoinHandle<Result<TxsOfSpkIndex, Error>>>>();

if handles.is_empty() {
if last_index.is_none() {
return Err(Box::new(esplora_client::Error::InvalidResponse));
}
break;
}

for handle in handles {
let (index, txs, evicted) = handle.join().expect("thread must not panic")?;
let handle_result = handle
.join()
.map_err(|_| Box::new(esplora_client::Error::InvalidResponse))?;
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Because you're dropping the error it won't be very informative to propagate it upward. Instead this module can define its own Error type to handle errors that aren't covered by esplora_client::Error.

let (index, txs, evicted) = handle_result?;
last_index = Some(index);
if !txs.is_empty() {
last_active_index = Some(index);
Expand All @@ -337,7 +343,8 @@ fn fetch_txs_with_keychain_spks<I: Iterator<Item = Indexed<SpkWithExpectedTxids>
.extend(evicted.into_iter().map(|txid| (txid, start_time)));
}

let last_index = last_index.expect("Must be set since handles wasn't empty.");
let last_index =
last_index.ok_or_else(|| Box::new(esplora_client::Error::InvalidResponse))?;
let gap_limit_reached = if let Some(i) = last_active_index {
last_index >= i.saturating_add(stop_gap as u32)
} else {
Expand Down Expand Up @@ -417,7 +424,10 @@ fn fetch_txs_with_txids<I: IntoIterator<Item = Txid>>(
}

for handle in handles {
let (txid, tx_info) = handle.join().expect("thread must not panic")?;
let handle_result = handle
.join()
.map_err(|_| Box::new(esplora_client::Error::InvalidResponse))?;
let (txid, tx_info) = handle_result?;
if let Some(tx_info) = tx_info {
if inserted_txs.insert(txid) {
update.txs.push(tx_info.to_tx().into());
Expand Down Expand Up @@ -478,7 +488,10 @@ fn fetch_txs_with_outpoints<I: IntoIterator<Item = OutPoint>>(
}

for handle in handles {
if let Some(op_status) = handle.join().expect("thread must not panic")? {
let handle_result = handle
.join()
.map_err(|_| Box::new(esplora_client::Error::InvalidResponse))?;
if let Some(op_status) = handle_result? {
let spend_txid = match op_status.txid {
Some(txid) => txid,
None => continue,
Expand Down Expand Up @@ -511,7 +524,7 @@ fn fetch_txs_with_outpoints<I: IntoIterator<Item = OutPoint>>(
#[cfg(test)]
#[cfg_attr(coverage_nightly, coverage(off))]
mod test {
use crate::blocking_ext::{chain_update, fetch_latest_blocks};
use crate::blocking_ext::{chain_update, fetch_latest_blocks, Error};
use bdk_chain::bitcoin;
use bdk_chain::bitcoin::hashes::Hash;
use bdk_chain::bitcoin::Txid;
Expand All @@ -529,6 +542,35 @@ mod test {
}};
}

#[test]
fn thread_join_panic_maps_to_error() {
let handle = std::thread::spawn(|| -> Result<(), Error> {
panic!("expected panic for test coverage");
});

let res = (|| -> Result<(), Error> {
let handle_result = handle
.join()
.map_err(|_| Box::new(esplora_client::Error::InvalidResponse))?;
handle_result?;
Ok(())
})();

assert!(matches!(
*res.unwrap_err(),
esplora_client::Error::InvalidResponse
));
}

#[test]
fn ensure_last_index_none_returns_error() {
let last_index: Option<u32> = None;
let err = last_index
.ok_or_else(|| Box::new(esplora_client::Error::InvalidResponse))
.unwrap_err();
assert!(matches!(*err, esplora_client::Error::InvalidResponse));
}

macro_rules! local_chain {
[ $(($height:expr, $block_hash:expr)), * ] => {{
#[allow(unused_mut)]
Expand Down
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