Cap listsinceblock target_confirmations param

Previously, listsinceblock would fail with error code -1 when the
target_confirmations exceeded the number of confirmations of the genesis
block. This commit allows target_confirmations to refer to a lastblock
hash with more confirmations than exist in the chain by setting the
lastblock hash to the genesis hash in this case. This allows for
`listsinceblock "" 6` to not fail if the block count is less than 5
which may happen on regtest.

Includes update to the functional test for listsinceblock to test for
this case.

1 files changed, 22 insertions, 0 deletions

diff --git a/test/functional/wallet_listsinceblock.py b/test/functional/wallet_listsinceblock.py
index 6d51ca6c93..d4131deabf 100755
--- a/test/functional/wallet_listsinceblock.py
+++ b/test/functional/wallet_listsinceblock.py
@@ -36,6 +36,7 @@ class ListSinceBlockTest(BitcoinTestFramework):
         self.test_double_spend()
         self.test_double_send()
         self.double_spends_filtered()
+        self.test_targetconfirmations()
 
     def test_no_blockhash(self):
         self.log.info("Test no blockhash")
@@ -74,6 +75,27 @@ class ListSinceBlockTest(BitcoinTestFramework):
         assert_raises_rpc_error(-8, "blockhash must be hexadecimal string (not 'Z000000000000000000000000000000000000000000000000000000000000000')", self.nodes[0].listsinceblock,
                                 "Z000000000000000000000000000000000000000000000000000000000000000")
 
+    def test_targetconfirmations(self):
+        '''
+        This tests when the value of target_confirmations exceeds the number of
+        blocks in the main chain. In this case, the genesis block hash should be
+        given for the `lastblock` property. If target_confirmations is < 1, then
+        a -8 invalid parameter error is thrown.
+        '''
+        self.log.info("Test target_confirmations")
+        blockhash, = self.nodes[2].generate(1)
+        blockheight = self.nodes[2].getblockheader(blockhash)['height']
+        self.sync_all()
+
+        assert_equal(
+            self.nodes[0].getblockhash(0),
+            self.nodes[0].listsinceblock(blockhash, blockheight + 1)['lastblock'])
+        assert_equal(
+            self.nodes[0].getblockhash(0),
+            self.nodes[0].listsinceblock(blockhash, blockheight + 1000)['lastblock'])
+        assert_raises_rpc_error(-8, "Invalid parameter",
+            self.nodes[0].listsinceblock, blockhash, 0)
+
     def test_reorg(self):
         '''
         `listsinceblock` did not behave correctly when handed a block that was