From 3a7c151674c487dd11f4f2d1db78d468f5f087a9 Mon Sep 17 00:00:00 2001
From: jp1ac4 <121959000+jp1ac4@users.noreply.github.com>
Date: Tue, 19 Mar 2024 10:45:32 +0000
Subject: [PATCH] database: allow for coinbase transactions to change addresses

`is_change` is `true` for a coin if its address is derived
from our change descriptor and could in principle be used for a
coinbase transaction.

The functional test was provided by darosior in a PR comment:
https://github.com/wizardsardine/liana/pull/1001#pullrequestreview-1948564150
---
 src/database/sqlite/mod.rs    |  2 +-
 src/database/sqlite/schema.rs |  9 ++-------
 tests/test_misc.py            | 14 ++++++++++++++
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/database/sqlite/mod.rs b/src/database/sqlite/mod.rs
index 0433c42e..52e660ad 100644
--- a/src/database/sqlite/mod.rs
+++ b/src/database/sqlite/mod.rs
@@ -1457,7 +1457,7 @@ CREATE TABLE spend_transactions (
                 block_info: None,
                 amount: bitcoin::Amount::from_sat(424242),
                 derivation_index: bip32::ChildNumber::from_normal_idx(4103).unwrap(),
-                is_change: false, // Cannot be both a coinbase deposit and change.
+                is_change: false,
                 spend_txid: None,
                 spend_block: None,
             };
diff --git a/src/database/sqlite/schema.rs b/src/database/sqlite/schema.rs
index 6add975a..ac101bcd 100644
--- a/src/database/sqlite/schema.rs
+++ b/src/database/sqlite/schema.rs
@@ -39,8 +39,8 @@ CREATE TABLE wallets (
  * transaction for this coin exists and was confirmed.
  *
  * The 'is_immature' field is for coinbase deposits that are not yet buried under 100
- * blocks. Note coinbase deposits can't be change. They also technically can't be
- * unconfirmed but we keep them as such until they become mature.
+ * blocks. Note coinbase deposits can't technically be unconfirmed but we keep them
+ * as such until they become mature.
  */
 CREATE TABLE coins (
     id INTEGER PRIMARY KEY NOT NULL,
@@ -56,7 +56,6 @@ CREATE TABLE coins (
     spend_block_height INTEGER,
     spend_block_time INTEGER,
     is_immature BOOLEAN NOT NULL CHECK (is_immature IN (0,1)),
-    CHECK (is_change IS 0 OR is_immature IS 0),
     UNIQUE (txid, vout),
     FOREIGN KEY (wallet_id) REFERENCES wallets (id)
         ON UPDATE RESTRICT
@@ -217,10 +216,6 @@ impl TryFrom<&rusqlite::Row<'_>> for DbCoin {
         });
 
         let is_immature: bool = row.get(12)?;
-        assert!(
-            !is_immature || !is_change,
-            "A coin cannot be both created in a coinbase and be change"
-        );
 
         Ok(DbCoin {
             id,
diff --git a/tests/test_misc.py b/tests/test_misc.py
index f4a81c5f..c7f29a6d 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -239,6 +239,20 @@ def test_coinbase_deposit(lianad, bitcoind):
         and coin["spend_info"] is not None
     )
 
+    # We must also properly detect coinbase deposits to a change address. We used to have
+    # an assertion that a coin cannot both be change and a coinbase deposit. Since change
+    # is determined by the address... Technically we can.
+    change_desc = lianad.multi_desc.singlepath_descriptors()[1]
+    change_addr = bitcoind.rpc.deriveaddresses(str(change_desc), [0, 0])[0]
+    bitcoind.rpc.generatetoaddress(1, change_addr)
+    wait_for(lambda: any(c["is_immature"] for c in lianad.rpc.listcoins()["coins"]))
+    coin = next(c for c in lianad.rpc.listcoins()["coins"] if c["is_immature"])
+    assert coin["is_change"]
+    bitcoind.generate_block(100)
+    wait_for_sync()
+    coin = next(c for c in lianad.rpc.listcoins()["coins"] if c["outpoint"] == coin["outpoint"])
+    assert not coin["is_immature"] and coin["block_height"] is not None
+
 
 @pytest.mark.skipif(
     OLD_LIANAD_PATH is None or USE_TAPROOT, reason="Need the old lianad binary to create the datadir."