Merge #1069: Implement Anchor for BlockId

18e8da3 docs: Add doctest for Anchor implementation on BlockId (Vladimir Fomene)
480c273 feat: Implement Anchor for BlockId (Vladimir Fomene)

Pull request description:

  ### Description

  This PR fixes #1062.
  It implements the `Anchor` trait on `BlockId`.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [x] I've added tests for the new feature
  * [x] I've added docs for the new feature

ACKs for top commit:
  evanlinjin:
    ACK 18e8da3

Tree-SHA512: af9da8b4e9c7f2a110340efa4e4c86d9b96ea1275f0a66f08e26a47fcacd89e318a32c845e2a4302f3332eeb4c6a976c3771b1d9881adf4feda90d6ba1a2dd9d

crates/chain/src/chain_data.rs

@@ -87,6 +87,9 @@ impl From<ChainPosition<ConfirmationTimeAnchor>> for ConfirmationTime {
 }
 
 /// A reference to a block in the canonical chain.
+///
+/// `BlockId` implements [`Anchor`]. When a transaction is anchored to `BlockId`, the confirmation
+/// block and anchor block are the same block.
 #[derive(Debug, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
 #[cfg_attr(
     feature = "serde",
@@ -100,6 +103,12 @@ pub struct BlockId {
     pub hash: BlockHash,
 }
 
+impl Anchor for BlockId {
+    fn anchor_block(&self) -> Self {
+        *self
+    }
+}
+
 impl Default for BlockId {
     fn default() -> Self {
         Self {
@@ -131,6 +140,8 @@ impl From<(&u32, &BlockHash)> for BlockId {
 }
 
 /// An [`Anchor`] implementation that also records the exact confirmation height of the transaction.
+///
+/// Refer to [`Anchor`] for more details.
 #[derive(Debug, Default, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
 #[cfg_attr(
     feature = "serde",
@@ -159,6 +170,8 @@ impl Anchor for ConfirmationHeightAnchor {
 
 /// An [`Anchor`] implementation that also records the exact confirmation time and height of the
 /// transaction.
+///
+/// Refer to [`Anchor`] for more details.
 #[derive(Debug, Default, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
 #[cfg_attr(
     feature = "serde",

crates/chain/src/tx_data_traits.rs

@@ -44,6 +44,58 @@ impl ForEachTxOut for Transaction {
 /// assume that transaction A is also confirmed in the best chain. This does not necessarily mean
 /// that transaction A is confirmed in block B. It could also mean transaction A is confirmed in a
 /// parent block of B.
+///
+/// ```
+/// # use bdk_chain::local_chain::LocalChain;
+/// # use bdk_chain::tx_graph::TxGraph;
+/// # use bdk_chain::BlockId;
+/// # use bdk_chain::ConfirmationHeightAnchor;
+/// # use bdk_chain::example_utils::*;
+/// # use bitcoin::hashes::Hash;
+///
+/// // Initialize the local chain with two blocks.
+/// let chain = LocalChain::from_blocks(
+///     [
+///         (1, Hash::hash("first".as_bytes())),
+///         (2, Hash::hash("second".as_bytes())),
+///     ]
+///     .into_iter()
+///     .collect(),
+/// );
+///
+/// // Transaction to be inserted into `TxGraph`s with different anchor types.
+/// let tx = tx_from_hex(RAW_TX_1);
+///
+/// // Insert `tx` into a `TxGraph` that uses `BlockId` as the anchor type.
+/// // When a transaction is anchored with `BlockId`, the anchor block and the confirmation block of
+/// // the transaction is the same block.
+/// let mut graph_a = TxGraph::<BlockId>::default();
+/// let _ = graph_a.insert_tx(tx.clone());
+/// graph_a.insert_anchor(
+///     tx.txid(),
+///     BlockId {
+///         height: 1,
+///         hash: Hash::hash("first".as_bytes()),
+///     },
+/// );
+///
+/// // Insert `tx` into a `TxGraph` that uses `ConfirmationHeightAnchor` as the anchor type.
+/// // When a transaction is anchored with `ConfirmationHeightAnchor`, the anchor block and
+/// // confirmation block can be different. However, the confirmation block cannot be higher than
+/// // the anchor block and both blocks must be in the same chain for the anchor to be valid.
+/// let mut graph_b = TxGraph::<ConfirmationHeightAnchor>::default();
+/// let _ = graph_b.insert_tx(tx.clone());
+/// graph_b.insert_anchor(
+///     tx.txid(),
+///     ConfirmationHeightAnchor {
+///         anchor_block: BlockId {
+///             height: 2,
+///             hash: Hash::hash("second".as_bytes()),
+///         },
+///         confirmation_height: 1,
+///     },
+/// );
+/// ```
 pub trait Anchor: core::fmt::Debug + Clone + Eq + PartialOrd + Ord + core::hash::Hash {
     /// Returns the [`BlockId`] that the associated blockchain data is "anchored" in.
     fn anchor_block(&self) -> BlockId;