fix: Remove collect, use DoubleEndedIterator

crates/bdk/src/wallet/mod.rs

@@ -985,7 +985,9 @@ impl Wallet {
     /// script pubkeys the wallet is storing internally).
     pub fn all_unbounded_spk_iters(
         &self,
-    ) -> BTreeMap<KeychainKind, impl Iterator<Item = (u32, ScriptBuf)> + Clone> {
+    ) -> impl DoubleEndedIterator<
+        Item = (KeychainKind, impl Iterator<Item = (u32, ScriptBuf)> + Clone),
+    > + '_ {
         self.indexed_graph.index.all_unbounded_spk_iters()
     }
 

crates/bdk/tests/wallet.rs

@@ -93,8 +93,11 @@ fn load_recovers_wallet() {
             wallet_spk_index.keychains().collect::<Vec<_>>()
         );
         assert_eq!(
-            wallet.spk_index().last_revealed_indices(),
-            wallet_spk_index.last_revealed_indices()
+            wallet
+                .spk_index()
+                .last_revealed_indices()
+                .collect::<Vec<_>>(),
+            wallet_spk_index.last_revealed_indices().collect::<Vec<_>>()
         );
         let secp = Secp256k1::new();
         assert_eq!(

crates/chain/src/keychain/txout_index.rs

@@ -575,11 +575,11 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     /// Get unbounded spk iterators for all keychains.
     pub fn all_unbounded_spk_iters(
         &self,
-    ) -> BTreeMap<K, SpkIterator<Descriptor<DescriptorPublicKey>>> {
+    ) -> impl DoubleEndedIterator<Item = (K, SpkIterator<Descriptor<DescriptorPublicKey>>)> + Clone + '_
+    {
         self.keychains_to_descriptors
             .iter()
             .map(|(k, (_, descriptor))| (k.clone(), SpkIterator::new(descriptor.clone())))
-            .collect()
     }
 
     /// Iterate over revealed spks of keychains in `range`
@@ -684,14 +684,11 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     /// Get the last derivation index that is revealed for each keychain.
     ///
     /// Keychains with no revealed indices will not be included in the returned [`BTreeMap`].
-    pub fn last_revealed_indices(&self) -> BTreeMap<K, u32> {
-        self.last_revealed
-            .iter()
-            .filter_map(|(desc_id, index)| {
-                let keychain = self.keychain_of_desc_id(desc_id)?;
-                Some((keychain.clone(), *index))
-            })
-            .collect()
+    pub fn last_revealed_indices(&self) -> impl DoubleEndedIterator<Item = (K, u32)> + '_ {
+        self.last_revealed.iter().filter_map(|(desc_id, index)| {
+            let keychain = self.keychain_of_desc_id(desc_id)?;
+            Some((keychain.clone(), *index))
+        })
     }
 
     /// Get the last derivation index revealed for `keychain`. Returns None if the keychain doesn't
@@ -923,14 +920,13 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
 
     /// Returns the highest derivation index of each keychain that [`KeychainTxOutIndex`] has found
     /// a [`TxOut`] with it's script pubkey.
-    pub fn last_used_indices(&self) -> BTreeMap<K, u32> {
+    pub fn last_used_indices(&self) -> impl DoubleEndedIterator<Item = (K, u32)> + '_ {
         self.keychains_to_descriptors
             .iter()
             .filter_map(|(keychain, _)| {
                 self.last_used_index(keychain)
                     .map(|index| (keychain.clone(), index))
             })
-            .collect()
     }
 
     /// Applies the derivation changeset to the [`KeychainTxOutIndex`], as specified in the

crates/chain/tests/test_keychain_txout_index.rs

@@ -162,7 +162,12 @@ fn test_set_all_derivation_indices() {
             last_revealed: last_revealed.clone()
         }
     );
-    assert_eq!(txout_index.last_revealed_indices(), derive_to);
+    assert_eq!(
+        txout_index
+            .last_revealed_indices()
+            .collect::<BTreeMap<_, _>>(),
+        derive_to
+    );
     assert_eq!(
         txout_index.reveal_to_target_multi(&derive_to).1,
         keychain::ChangeSet::default(),
@@ -738,8 +743,8 @@ fn applying_changesets_one_by_one_vs_aggregate_must_have_same_result() {
         indexer_b.spk_at_index(TestKeychain::Internal, 0)
     );
     assert_eq!(
-        indexer_a.last_revealed_indices(),
-        indexer_b.last_revealed_indices()
+        indexer_a.last_revealed_indices().collect::<Vec<_>>(),
+        indexer_b.last_revealed_indices().collect::<Vec<_>>(),
     );
 }