[BarbieRajput]

Description

Fixes #2459.

fetch_txs_with_outpoints calls HashSet::<Txid>::with_capacity(..). Without the std feature, bdk_core::collections::HashSet is an alias for BTreeSet, which has no with_capacity, so bdk_esplora fails to compile with blocking or async unless std is also enabled.

This PR uses HashSet::<Txid>::new() in both blocking_ext.rs and async_ext.rs, which works for either collection type.

Notes to the reviewers

This has no regression test because dev-dependencies enable bdk_core/std, so test builds can't reproduce it. I checked it with:

cargo check -p bdk_esplora --no-default-features --features <feature>

for blocking, async, blocking-https, blocking-https-rustls, blocking-https-native, async-https, async-https-rustls and async-https-native. All 8 failed before this change and pass now. cargo test -p bdk_esplora --all-features also passes.

Published bdk_esplora 0.22.3 is affected too, so this needs a backport to release/chain-0.23.x.

CI currently builds async/blocking only together with std. An alternative fix is to make those features imply std in Cargo.toml. I went with HashSet::new because it's the smaller change and keeps std optional. Happy to switch if you prefer that.

I can also add a CI step (cargo build --no-default-features --features blocking / async) to catch this in future, either here as a separate commit or in a follow-up PR.

Changelog notice

Fixed

• bdk_esplora: blocking and async features compile again without std. fix(esplora): use HashSet::new in fetch_txs_with_outpoints #2460

Checklists

All Submissions:

• I followed the contribution guidelines

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR