[backport] Add get_pre_1_wallet_keychains migration helper

wallet/src/wallet/migration.rs

@@ -0,0 +1,138 @@
+// Bitcoin Dev Kit
+//
+// Copyright (c) 2020-2026 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Migration utilities for upgrading between BDK library versions.
+//!
+//! This module provides helper functions and types to assist users in migrating wallet data
+//! when upgrading between major versions of the `bdk_wallet` crate.
+
+#[cfg(feature = "rusqlite")]
+use crate::rusqlite::{self, Connection};
+#[cfg(feature = "rusqlite")]
+use alloc::{string::String, string::ToString, vec::Vec};
+
+// pre-1.0 sqlite database migration helper functions
+
+/// `Pre1WalletKeychain` represents a structure that holds the keychain details
+/// and metadata required for managing a wallet's keys.
+#[cfg(feature = "rusqlite")]
+#[derive(Debug)]
+pub struct Pre1WalletKeychain {
+    /// The name of the wallet keychains, "External" or "Internal".
+    pub keychain: String,
+    /// The index of the last derived key in the wallet keychain.
+    pub last_derivation_index: u32,
+    /// Checksum of the keychain descriptor, it must match the corresponding post-1.0 bdk wallet
+    /// descriptor checksum.
+    pub checksum: Vec<u8>,
+}
+
+/// Retrieves a list of [`Pre1WalletKeychain`] objects from a pre-1.0 bdk SQLite database.
+///
+/// This function uses a connection to a pre-1.0 bdk wallet SQLite database to execute a query that
+/// retrieves data from two tables (`last_derivation_indices` and `checksums`) and maps the
+/// resulting rows to a list of `Pre1WalletKeychain` objects.
+#[cfg(feature = "rusqlite")]
+pub fn get_pre_1_wallet_keychains(
+    conn: &mut Connection,
+) -> Result<Vec<Pre1WalletKeychain>, rusqlite::Error> {
+    let db_tx = conn.transaction()?;
+    let mut statement = db_tx.prepare(
+        "SELECT idx.keychain AS keychain, value, checksum FROM last_derivation_indices AS idx \
+         JOIN checksums AS chk ON idx.keychain = chk.keychain",
+    )?;
+    let row_iter = statement.query_map([], |row| {
+        Ok((
+            row.get::<_, String>("keychain")?,
+            row.get::<_, u32>("value")?,
+            row.get::<_, Vec<u8>>("checksum")?,
+        ))
+    })?;
+    let mut keychains = vec![];
+    for row in row_iter {
+        let (keychain, value, checksum) = row?;
+        keychains.push(Pre1WalletKeychain {
+            keychain: keychain.trim_matches('"').to_string(),
+            last_derivation_index: value,
+            checksum,
+        })
+    }
+    Ok(keychains)
+}
+
+#[cfg(test)]
+mod test {
+    #[cfg(feature = "rusqlite")]
+    use crate::rusqlite::{self, Connection};
+
+    #[cfg(feature = "rusqlite")]
+    #[test]
+    fn test_get_pre_1_wallet_keychains() -> anyhow::Result<()> {
+        let mut conn = Connection::open_in_memory()?;
+        let external_checksum = vec![0x01u8, 0x02u8, 0x03u8, 0x04u8];
+        let internal_checksum = vec![0x05u8, 0x06u8, 0x07u8, 0x08u8];
+        // Init tables
+        {
+            // Create pre-1.0 bdk sqlite schema
+            conn.execute_batch(
+                "CREATE TABLE last_derivation_indices (keychain TEXT, value INTEGER);
+                 CREATE UNIQUE INDEX idx_indices_keychain ON last_derivation_indices(keychain);
+                 CREATE TABLE checksums (keychain TEXT, checksum BLOB);
+                 CREATE INDEX idx_checksums_keychain ON checksums(keychain);",
+            )?;
+            // Insert test data
+            conn.execute(
+                "INSERT INTO last_derivation_indices (keychain, value) VALUES (?, ?)",
+                rusqlite::params!["\"External\"", 42],
+            )?;
+            conn.execute(
+                "INSERT INTO checksums (keychain, checksum) VALUES (?, ?)",
+                rusqlite::params!["\"External\"", external_checksum],
+            )?;
+            conn.execute(
+                "INSERT INTO last_derivation_indices (keychain, value) VALUES (?, ?)",
+                rusqlite::params!["\"Internal\"", 21],
+            )?;
+            conn.execute(
+                "INSERT INTO checksums (keychain, checksum) VALUES (?, ?)",
+                rusqlite::params!["\"Internal\"", internal_checksum],
+            )?;
+        }
+
+        // test with a 2 keychain wallet
+        let result = super::get_pre_1_wallet_keychains(&mut conn)?;
+        assert_eq!(result.len(), 2);
+        assert_eq!(result[0].keychain, "External");
+        assert_eq!(result[0].last_derivation_index, 42);
+        assert_eq!(result[0].checksum, external_checksum);
+        assert_eq!(result[1].keychain, "Internal");
+        assert_eq!(result[1].last_derivation_index, 21);
+        assert_eq!(result[1].checksum, internal_checksum);
+        // delete "Internal" descriptor
+        {
+            conn.execute(
+                "DELETE FROM last_derivation_indices WHERE keychain = ?",
+                rusqlite::params!["\"Internal\""],
+            )?;
+            conn.execute(
+                "DELETE FROM checksums WHERE keychain = ?",
+                rusqlite::params!["\"Internal\""],
+            )?;
+        }
+        // test with a 1 keychain wallet
+        let result = super::get_pre_1_wallet_keychains(&mut conn)?;
+        assert_eq!(result.len(), 1);
+        assert_eq!(result[0].keychain, "External");
+        assert_eq!(result[0].last_derivation_index, 42);
+        assert_eq!(result[0].checksum, external_checksum);
+
+        Ok(())
+    }
+}

wallet/src/wallet/mod.rs

@@ -54,6 +54,7 @@ pub mod coin_selection;
 pub mod error;
 pub mod event;
 pub mod export;
+pub mod migration;
 mod params;
 mod persisted;
 #[deprecated(