Merge bitcoin/bitcoin#24845: wallet: return error msg for "too-long-mempool-chain"

f3221d373a8623fe4808e00c7a92fbb6e0d6419b test: add wallet too-long-mempool-chain error coverage (furszy)
acf0119d24c9f8fae825093249a46cd38e4a3a91 wallet: return error msg for too-long-mempool-chain failure (furszy)

Pull request description:

  Fixes #23144.

  We currently return a general "Insufficient funds" from Coin
  Selection when we actually skipped unconfirmed UTXOs that
  surpassed the mempool ancestors limit.

  This PR make the error clearer by returning:
  "Unconfirmed UTXOs are available, but spending them creates
  a chain of transactions that will be rejected by the mempool"

  Also, added an early return from Coin Selection if the sum of
  the discarded coins decreases the available balance below the
  target amount.

ACKs for top commit:
  achow101:
    ACK f3221d373a8623fe4808e00c7a92fbb6e0d6419b
  S3RK:
    Code review ACK f3221d373a8623fe4808e00c7a92fbb6e0d6419b
  Xekyo:
    ACK f3221d373a8623fe4808e00c7a92fbb6e0d6419b

Tree-SHA512: 13e5824b75ac302280ff894560a4ebf32a74f32fe49ef8281f2bc99c0104b92cef33d3b143c6e131f3a07eafe64533af7fc60abff585142c134b9d6e531a6a66

1 files changed, 25 insertions, 0 deletions

diff --git a/test/functional/wallet_create_tx.py b/test/functional/wallet_create_tx.py
index 2d9bb38fcc..11c82e15b7 100755
--- a/test/functional/wallet_create_tx.py
+++ b/test/functional/wallet_create_tx.py
@@ -32,6 +32,7 @@ class CreateTxWalletTest(BitcoinTestFramework):
 
         self.test_anti_fee_sniping()
         self.test_tx_size_too_large()
+        self.test_create_too_long_mempool_chain()
 
     def test_anti_fee_sniping(self):
         self.log.info('Check that we have some (old) blocks and that anti-fee-sniping is disabled')
@@ -80,6 +81,30 @@ class CreateTxWalletTest(BitcoinTestFramework):
         )
         self.nodes[0].settxfee(0)
 
+    def test_create_too_long_mempool_chain(self):
+        self.log.info('Check too-long mempool chain error')
+        df_wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+
+        self.nodes[0].createwallet("too_long")
+        test_wallet = self.nodes[0].get_wallet_rpc("too_long")
+
+        tx_data = df_wallet.send(outputs=[{test_wallet.getnewaddress(): 25}], options={"change_position": 0})
+        txid = tx_data['txid']
+        vout = 1
+
+        options = {"change_position": 0, "add_inputs": False}
+        for i in range(1, 25):
+            options['inputs'] = [{'txid': txid, 'vout': vout}]
+            tx_data = test_wallet.send(outputs=[{test_wallet.getnewaddress(): 25 - i}], options=options)
+            txid = tx_data['txid']
+
+        # Sending one more chained transaction will fail
+        options = {"minconf": 0, "include_unsafe": True, 'add_inputs': True}
+        assert_raises_rpc_error(-4, "Unconfirmed UTXOs are available, but spending them creates a chain of transactions that will be rejected by the mempool",
+                                test_wallet.send, outputs=[{test_wallet.getnewaddress(): 0.3}], options=options)
+
+        test_wallet.unloadwallet()
+
 
 if __name__ == '__main__':
     CreateTxWalletTest().main()