feat!: Add #[non_exhaustive] to ChangeSet structs in tx_graph, keychain_txout, local_chain

Add #[non_exhaustive] attribute to the ChangeSet structs to prevent downstream
crates from exhaustively matching or constructing instances using struct
literal syntax, allowing future additions without breaking compatibility.

The change improves forward compatibility by allowing new fields to be added
without breaking downstream code in future releases.

Author: notmandatory

crates/bitcoind_rpc/tests/test_emitter.rs

@@ -102,11 +102,10 @@ pub fn test_sync_local_chain() -> anyhow::Result<()> {
         assert_eq!(
             local_chain.apply_update(emission.checkpoint,)?,
             if exp_height == exp_hashes.len() - reorged_blocks.len() {
-                bdk_chain::local_chain::ChangeSet {
-                    blocks: core::iter::once((height, Some(hash)))
-                        .chain((height + 1..exp_hashes.len() as u32).map(|h| (h, None)))
-                        .collect(),
-                }
+                bdk_chain::local_chain::ChangeSet::from(
+                    core::iter::once((height, Some(hash)))
+                        .chain((height + 1..exp_hashes.len() as u32).map(|h| (h, None))),
+                )
             } else {
                 [(height, Some(hash))].into()
             },

crates/chain/src/indexed_tx_graph.rs

@@ -482,6 +482,7 @@ impl<A, I> AsRef<TxGraph<A>> for IndexedTxGraph<A, I> {
     ))
 )]
 #[must_use]
+#[non_exhaustive]
 pub struct ChangeSet<A, IA> {
     /// [`TxGraph`] changeset.
     pub tx_graph: tx_graph::ChangeSet<A>,

crates/chain/src/indexer/keychain_txout.rs

@@ -1021,6 +1021,7 @@ impl<K: core::fmt::Debug> std::error::Error for InsertDescriptorError<K> {}
 #[derive(Clone, Debug, Default, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[must_use]
+#[non_exhaustive]
 pub struct ChangeSet {
     /// Maps each `DescriptorId` to its last revealed derivation index.
     pub last_revealed: BTreeMap<DescriptorId, u32>,
@@ -1031,6 +1032,19 @@ pub struct ChangeSet {
     pub spk_cache: BTreeMap<DescriptorId, BTreeMap<u32, ScriptBuf>>,
 }
 
+impl ChangeSet {
+    /// Create a new empty `ChangeSet`.
+    pub fn new(
+        last_revealed: BTreeMap<DescriptorId, u32>,
+        spk_cache: BTreeMap<DescriptorId, BTreeMap<u32, ScriptBuf>>,
+    ) -> Self {
+        Self {
+            last_revealed,
+            spk_cache,
+        }
+    }
+}
+
 impl Merge for ChangeSet {
     /// Merge another [`ChangeSet`] into self.
     fn merge(&mut self, other: Self) {

crates/chain/src/local_chain.rs

@@ -408,6 +408,7 @@ impl LocalChain {
 /// The [`ChangeSet`] represents changes to [`LocalChain`].
 #[derive(Debug, Default, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[non_exhaustive]
 pub struct ChangeSet {
     /// Changes to the [`LocalChain`] blocks.
     ///

crates/chain/src/tx_graph.rs

@@ -173,6 +173,7 @@ impl<A: Anchor> From<TxUpdate<A>> for TxGraph<A> {
 ///
 /// [module-level documentation]: crate::tx_graph
 #[derive(Clone, Debug, PartialEq)]
+#[non_exhaustive]
 pub struct TxGraph<A = ConfirmationBlockTime> {
     txs: HashMap<Txid, TxNodeInternal>,
     spends: BTreeMap<OutPoint, HashSet<Txid>>,
@@ -1415,6 +1416,7 @@ impl<A: Anchor> TxGraph<A> {
     ))
 )]
 #[must_use]
+#[non_exhaustive]
 pub struct ChangeSet<A = ()> {
     /// Added transactions.
     pub txs: BTreeSet<Arc<Transaction>>,

crates/chain/tests/test_indexed_tx_graph.rs

@@ -5,11 +5,12 @@ mod common;
 
 use std::{collections::BTreeSet, sync::Arc};
 
+use bdk_chain::indexed_tx_graph::ChangeSet;
 use bdk_chain::{
     indexed_tx_graph::{self, IndexedTxGraph},
     indexer::keychain_txout::KeychainTxOutIndex,
     local_chain::LocalChain,
-    tx_graph, Balance, CanonicalizationParams, ChainPosition, ConfirmationBlockTime, DescriptorExt,
+    Balance, CanonicalizationParams, ChainPosition, ConfirmationBlockTime, DescriptorExt,
     SpkIterator,
 };
 use bdk_testenv::{
@@ -74,45 +75,41 @@ fn insert_relevant_txs() {
 
     let txs = [tx_c, tx_b, tx_a];
 
-    let changeset = indexed_tx_graph::ChangeSet {
-        tx_graph: tx_graph::ChangeSet {
-            txs: txs.iter().cloned().map(Arc::new).collect(),
-            ..Default::default()
-        },
-        indexer: keychain_txout::ChangeSet {
-            last_revealed: [(descriptor.descriptor_id(), 9_u32)].into(),
-            spk_cache: [(descriptor.descriptor_id(), {
-                let index_after_spk_1 = 9 /* index of spk_1 */ + 1;
-                SpkIterator::new_with_range(
-                    &descriptor,
-                    // This will also persist the staged spk cache inclusions from prev call to
-                    // `.insert_descriptor`.
-                    0..index_after_spk_1 + lookahead,
-                )
-                .collect()
-            })]
-            .into(),
-        },
-    };
+    let mut changeset = ChangeSet::default();
+    changeset
+        .tx_graph
+        .txs
+        .extend(txs.iter().cloned().map(Arc::new));
+    let mut indexer_changeset = keychain_txout::ChangeSet::default();
+    indexer_changeset.last_revealed = [(descriptor.descriptor_id(), 9_u32)].into();
+    indexer_changeset.spk_cache = [(descriptor.descriptor_id(), {
+        let index_after_spk_1 = 9 /* index of spk_1 */ + 1;
+        SpkIterator::new_with_range(
+            &descriptor,
+            // This will also persist the staged spk cache inclusions from prev call to
+            // `.insert_descriptor`.
+            0..index_after_spk_1 + lookahead,
+        )
+        .collect()
+    })]
+    .into();
+    changeset.indexer = indexer_changeset.into();
 
     assert_eq!(
         graph.batch_insert_relevant(txs.iter().cloned().map(|tx| (tx, None))),
         changeset,
     );
 
     // The initial changeset will also contain info about the keychain we added
-    let initial_changeset = indexed_tx_graph::ChangeSet {
-        tx_graph: changeset.tx_graph,
-        indexer: keychain_txout::ChangeSet {
-            last_revealed: changeset.indexer.last_revealed,
-            spk_cache: [(
-                descriptor.descriptor_id(),
-                SpkIterator::new_with_range(&descriptor, 0..=9 /* index of spk_1*/  + lookahead)
-                    .collect(),
-            )]
-            .into(),
-        },
-    };
+    let mut initial_changeset = indexed_tx_graph::ChangeSet::default();
+    initial_changeset.tx_graph = changeset.tx_graph;
+    initial_changeset.indexer = keychain_txout::ChangeSet::default();
+    initial_changeset.indexer.last_revealed = changeset.indexer.last_revealed;
+    initial_changeset.indexer.spk_cache = [(
+        descriptor.descriptor_id(),
+        SpkIterator::new_with_range(&descriptor, 0..=9 /*index of spk_1 */ + lookahead).collect(),
+    )]
+    .into();
 
     assert_eq!(graph.initial_changeset(), initial_changeset);
 }

crates/chain/tests/test_keychain_txout_index.rs

@@ -80,14 +80,12 @@ fn merge_changesets_check_last_revealed() {
     rhs_di.insert(descriptor_ids[1], 5); // value more than lhs desc 1
     lhs_di.insert(descriptor_ids[3], 4); // key doesn't exist in lhs
 
-    let mut lhs = ChangeSet {
-        last_revealed: lhs_di,
-        ..Default::default()
-    };
-    let rhs = ChangeSet {
-        last_revealed: rhs_di,
-        ..Default::default()
-    };
+    let mut lhs = ChangeSet::default();
+    lhs.last_revealed = lhs_di;
+
+    let mut rhs = ChangeSet::default();
+    rhs.last_revealed = rhs_di;
+
     lhs.merge(rhs);
 
     // Existing index doesn't update if the new index in `other` is lower than `self`.
@@ -129,12 +127,13 @@ fn test_set_all_derivation_indices() {
         ),
     ]
     .into();
+
+    let mut expected_changeset = ChangeSet::default();
+    expected_changeset.last_revealed = last_revealed.clone();
+    expected_changeset.spk_cache = spk_cache.clone();
     assert_eq!(
         txout_index.reveal_to_target_multi(&derive_to),
-        ChangeSet {
-            last_revealed: last_revealed.clone(),
-            spk_cache: spk_cache.clone(),
-        }
+        expected_changeset
     );
     assert_eq!(txout_index.last_revealed_indices(), derive_to);
     assert_eq!(
@@ -629,16 +628,11 @@ fn lookahead_to_target() {
 #[test]
 fn applying_changesets_one_by_one_vs_aggregate_must_have_same_result() {
     let desc = parse_descriptor(DESCRIPTORS[0]);
-    let changesets: &[ChangeSet] = &[
-        ChangeSet {
-            last_revealed: [(desc.descriptor_id(), 10)].into(),
-            ..Default::default()
-        },
-        ChangeSet {
-            last_revealed: [(desc.descriptor_id(), 12)].into(),
-            ..Default::default()
-        },
-    ];
+    let mut changeset_1 = ChangeSet::default();
+    changeset_1.last_revealed = [(desc.descriptor_id(), 10)].into();
+    let mut changeset_2 = ChangeSet::default();
+    changeset_2.last_revealed = [(desc.descriptor_id(), 12)].into();
+    let changesets: &[ChangeSet] = &[changeset_1, changeset_2];
 
     let mut indexer_a = KeychainTxOutIndex::<TestKeychain>::new(0, true);
     let _ = indexer_a