Repository: bitcoin/bitcoin
File: test/functional/rpc_invalidateblock.py (Python)

Code before:
        besthash_n0 = self.nodes[0].getbestblockhash()

        self.log.info("Mine competing 6 blocks on Node 1")
        self.generate(self.nodes[1], 6, sync_fun=self.no_op)
        assert_equal(self.nodes[1].getblockcount(), 6)

        self.log.info("Connect nodes to force a reorg")
        self.connect_nodes(0, 1)
        self.sync_blocks(self.nodes[0:2])
        assert_equal(self.nodes[0].getblockcount(), 6)
        badhash = self.nodes[1].getblockhash(2)

        self.log.info("Invalidate block 2 on node 0 and verify we reorg to node 0's original chain")
        self.nodes[0].invalidateblock(badhash)
        assert_equal(self.nodes[0].getblockcount(), 4)
        assert_equal(self.nodes[0].getbestblockhash(), besthash_n0)

        self.log.info("Make sure we won't reorg to a lower work chain:")
        self.connect_nodes(1, 2)
        self.log.info("Sync node 2 to node 1 so both have 6 blocks")
        self.sync_blocks(self.nodes[1:3])
        assert_equal(self.nodes[2].getblockcount(), 6)
        self.log.info("Invalidate block 5 on node 1 so its tip is now at 4")
        self.nodes[1].invalidateblock(self.nodes[1].getblockhash(5))
        assert_equal(self.nodes[1].getblockcount(), 4)
        self.log.info("Invalidate block 3 on node 2, so its tip is now 2")
        self.nodes[2].invalidateblock(self.nodes[2].getblockhash(3))
        assert_equal(self.nodes[2].getblockcount(), 2)
        self.log.info("..and then mine a block")
        self.generate(self.nodes[2], 1, sync_fun=self.no_op)
        self.log.info("Verify all nodes are at the right height")
        self.wait_until(lambda: self.nodes[2].getblockcount() == 3, timeout=5)
        self.wait_until(lambda: self.nodes[0].getblockcount() == 4, timeout=5)
        self.wait_until(lambda: self.nodes[1].getblockcount() == 4, timeout=5)

        self.log.info("Verify that we reconsider all ancestors as well")
        blocks = self.generatetodescriptor(self.nodes[1], 10, ADDRESS_BCRT1_UNSPENDABLE_DESCRIPTOR, sync_fun=self.no_op)
        assert_equal(self.nodes[1].getbestblockhash(), blocks[-1])
        # Invalidate the two blocks at the tip
        self.nodes[1].invalidateblock(blocks[-1])
        self.nodes[1].invalidateblock(blocks[-2])
        assert_equal(self.nodes[1].getbestblockhash(), blocks[-3])
        # Reconsider only the previous tip
        self.nodes[1].reconsiderblock(blocks[-1])
        # Should be back at the tip by now
        assert_equal(self.nodes[1].getbestblockhash(), blocks[-1])

        self.log.info("Verify that we reconsider all descendants")
        blocks = self.generatetodescriptor(self.nodes[1], 10, ADDRESS_BCRT1_UNSPENDABLE_DESCRIPTOR, sync_fun=self.no_op)
        assert_equal(self.nodes[1].getbestblockhash(), blocks[-1])
        # Invalidate the two blocks at the tip

Review comment (bug):
It might be a good idea to expand this a bit:
```diff
@@ -45 +45 @@ class InvalidateTest(BitcoinTestFramework):
-        tip = int(self.nodes[0].getbestblockhash(), 16)
+        tip = self.nodes[0].getbestblockhash()
@@ -47 +47 @@ class InvalidateTest(BitcoinTestFramework):
-        block = create_block(tip, create_coinbase(self.nodes[0].getblockcount()), block_time, version=4)
+        block = create_block(int(tip, 16), create_coinbase(self.nodes[0].getblockcount()), block_time, version=4)
@@ -49,0 +50 @@ class InvalidateTest(BitcoinTestFramework):
+        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"] + 1)
@@ -56,0 +58,11 @@ class InvalidateTest(BitcoinTestFramework):
+        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"])
+
+        self.log.info("Reconsider block 6 on node 0 again and verify that the best header is set correctly")
+        self.nodes[0].reconsiderblock(tip)
+        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"] + 1)
+
+        self.log.info("Invalid block 2 on node 0 and verify we reorg to node 0's original chain again")
+        self.nodes[0].invalidateblock(badhash)
+        assert_equal(self.nodes[0].getblockcount(), 4)
+        assert_equal(self.nodes[0].getbestblockhash(), besthash_n0)
+        # Should report consistent blockchain info
```
This additionally checks that the new header can be reconsidered again correctly (`BLOCK_FAILED_CHILD` is indeed reset). It's a bit verbose and repetitive though and following along with the various chainstates is already a bit annoying, so not sure if it delivers enough value.

Code after:
        self.log.info("Make sure we repopulate setBlockIndexCandidates after InvalidateBlock:")
        self.log.info("Mine 4 blocks on Node 0")
        self.generate(self.nodes[0], 4, sync_fun=self.no_op)
        assert_equal(self.nodes[0].getblockcount(), 4)
        besthash_n0 = self.nodes[0].getbestblockhash()

        self.log.info("Mine competing 6 blocks on Node 1")
        self.generate(self.nodes[1], 6, sync_fun=self.no_op)
        assert_equal(self.nodes[1].getblockcount(), 6)

        self.log.info("Connect nodes to force a reorg")
        self.connect_nodes(0, 1)
        self.sync_blocks(self.nodes[0:2])
        assert_equal(self.nodes[0].getblockcount(), 6)

        # Add a header to the tip of node 0 without submitting the block. This shouldn't
        # affect results since this chain will be invalidated next.
        tip = self.nodes[0].getbestblockhash()
        block_time = self.nodes[0].getblock(self.nodes[0].getbestblockhash())['time'] + 1
        block = create_block(int(tip, 16), create_coinbase(self.nodes[0].getblockcount()), block_time, version=4)
        block.solve()
        self.nodes[0].submitheader(block.serialize().hex())
        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"] + 1)

        self.log.info("Invalidate block 2 on node 0 and verify we reorg to node 0's original chain")
        badhash = self.nodes[1].getblockhash(2)
        self.nodes[0].invalidateblock(badhash)
        assert_equal(self.nodes[0].getblockcount(), 4)
        assert_equal(self.nodes[0].getbestblockhash(), besthash_n0)
        # Should report consistent blockchain info
        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"])

        self.log.info("Reconsider block 6 on node 0 again and verify that the best header is set correctly")
        self.nodes[0].reconsiderblock(tip)
        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"] + 1)

        self.log.info("Invalidate block 2 on node 0 and verify we reorg to node 0's original chain again")
        self.nodes[0].invalidateblock(badhash)
        assert_equal(self.nodes[0].getblockcount(), 4)
        assert_equal(self.nodes[0].getbestblockhash(), besthash_n0)
        assert_equal(self.nodes[0].getblockchaininfo()["headers"], self.nodes[0].getblockchaininfo()["blocks"])

        self.log.info("Make sure we won't reorg to a lower work chain:")
        self.connect_nodes(1, 2)
        self.log.info("Sync node 2 to node 1 so both have 6 blocks")
        self.sync_blocks(self.nodes[1:3])
        assert_equal(self.nodes[2].getblockcount(), 6)
        self.log.info("Invalidate block 5 on node 1 so its tip is now at 4")
        self.nodes[1].invalidateblock(self.nodes[1].getblockhash(5))
        assert_equal(self.nodes[1].getblockcount(), 4)
        self.log.info("Invalidate block 3 on node 2, so its tip is now 2")