Merge bitcoin/bitcoin#30817: test: Add coverage for dumptxoutset failure robustness

c2b779da4e refactor: Manage dumptxoutset RAII classes with std::optional (Fabian Jahr)
4b5bf335ad test: Add coverage for failing dumptxoutset behavior (Fabian Jahr)

Pull request description:

  This adds a test that checks that network activity is not suspended if dumptxoutset fails in the middle of its process which is implemented with the `NetworkDisable` RAII class. I would have liked to add coverage for the `TemporaryRollback` RAII class but that seems a lot more tricky since the failure needs to happen at some point after the rollback and on the scale of our test chain here I couldn't find a way to do it yet. This was requested by pablomartin4btc here: https://github.com/bitcoin/bitcoin/pull/30808#pullrequestreview-2280450117. To test the test you can comment out the content of the destructor of `NetworkDisable`.

  It also addresses the feedback by ryanofsky to use `std::optional` instead of `std::unique_ptr` for the management of the RAII object: https://github.com/bitcoin/bitcoin/pull/30808#discussion_r1744149228

ACKs for top commit:
  achow101:
    ACK c2b779da4e
  pablomartin4btc:
    cr & tACK c2b779da4e
  tdb3:
    ACK c2b779da4e
  BrandonOdiwuor:
    Code Review ACK c2b779da4e
  theStack:
    ACK c2b779da4e

Tree-SHA512: 9556e75014a2599bb870b70faf887608b332f2312626333f771d4ec11c04f863a2cf17e223ec473d4e8b0c9e8008394a4e0c321561f7ef3a2eec713dcfaea58a

src/rpc/blockchain.cpp

@@ -56,6 +56,7 @@
 #include <condition_variable>
 #include <memory>
 #include <mutex>
+#include <optional>
 
 using kernel::CCoinsStats;
 using kernel::CoinStatsHashType;
@@ -2786,8 +2787,8 @@ static RPCHelpMan dumptxoutset()
 
     CConnman& connman = EnsureConnman(node);
     const CBlockIndex* invalidate_index{nullptr};
-    std::unique_ptr<NetworkDisable> disable_network;
-    std::unique_ptr<TemporaryRollback> temporary_rollback;
+    std::optional<NetworkDisable> disable_network;
+    std::optional<TemporaryRollback> temporary_rollback;
 
     // If the user wants to dump the txoutset of the current tip, we don't have
     // to roll back at all
@@ -2812,18 +2813,16 @@ static RPCHelpMan dumptxoutset()
         // automatically re-enables the network activity at the end of the
         // process which may not be what the user wants.
         if (connman.GetNetworkActive()) {
-            disable_network = std::make_unique<NetworkDisable>(connman);
+            disable_network.emplace(connman);
         }
 
         invalidate_index = WITH_LOCK(::cs_main, return node.chainman->ActiveChain().Next(target_index));
-        temporary_rollback = std::make_unique<TemporaryRollback>(*node.chainman, *invalidate_index);
+        temporary_rollback.emplace(*node.chainman, *invalidate_index);
     }
 
     Chainstate* chainstate;
     std::unique_ptr<CCoinsViewCursor> cursor;
     CCoinsStats stats;
-    UniValue result;
-    UniValue error;
     {
         // Lock the chainstate before calling PrepareUtxoSnapshot, to be able
         // to get a UTXO database cursor while the chain is pointing at the
@@ -2847,7 +2846,7 @@ static RPCHelpMan dumptxoutset()
         }
     }
 
-    result = WriteUTXOSnapshot(*chainstate, cursor.get(), &stats, tip, afile, path, temppath, node.rpc_interruption_point);
+    UniValue result = WriteUTXOSnapshot(*chainstate, cursor.get(), &stats, tip, afile, path, temppath, node.rpc_interruption_point);
     fs::rename(temppath, path);
 
     result.pushKV("path", path.utf8string());

test/functional/rpc_dumptxoutset.py

@@ -28,7 +28,7 @@ class DumptxoutsetTest(BitcoinTestFramework):
 
         FILENAME = 'txoutset.dat'
         out = node.dumptxoutset(FILENAME, "latest")
-        expected_path = node.datadir_path / self.chain / FILENAME
+        expected_path = node.chain_path / FILENAME
 
         assert expected_path.is_file()
 
@@ -60,6 +60,16 @@ class DumptxoutsetTest(BitcoinTestFramework):
         assert_raises_rpc_error(
             -8, 'Invalid snapshot type "bogus" specified. Please specify "rollback" or "latest"', node.dumptxoutset, 'utxos.dat', "bogus")
 
+        self.log.info(f"Test that dumptxoutset failure does not leave the network activity suspended")
+        rev_file = node.blocks_path / "rev00000.dat"
+        bogus_file = node.blocks_path / "bogus.dat"
+        rev_file.rename(bogus_file)
+        assert_raises_rpc_error(
+            -1, 'Could not roll back to requested height.', node.dumptxoutset, 'utxos.dat', rollback=99)
+        assert_equal(node.getnetworkinfo()['networkactive'], True)
+
+        # Cleanup
+        bogus_file.rename(rev_file)
 
 if __name__ == '__main__':
     DumptxoutsetTest(__file__).main()