wallet: Avoid use of Chain::Lock in importprunedfunds

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip, in which case the "Block not found in chain" error
will be stricter and not allow importing data from a blocks between the wallet
last processed tip and the current node tip.

src/interfaces/chain.cpp

@@ -267,6 +267,14 @@ public:
         WAIT_LOCK(cs_main, lock);
         return FillBlock(LookupBlockIndex(hash), block, lock);
     }
+    bool findAncestorByHash(const uint256& block_hash, const uint256& ancestor_hash, const FoundBlock& ancestor_out) override
+    {
+        WAIT_LOCK(cs_main, lock);
+        const CBlockIndex* block = LookupBlockIndex(block_hash);
+        const CBlockIndex* ancestor = LookupBlockIndex(ancestor_hash);
+        if (block && ancestor && block->GetAncestor(ancestor->nHeight) != ancestor) ancestor = nullptr;
+        return FillBlock(ancestor, ancestor_out, lock);
+    }
     void findCoins(std::map<COutPoint, Coin>& coins) override { return FindCoins(m_node, coins); }
     double guessVerificationProgress(const uint256& block_hash) override
     {

src/interfaces/chain.h

@@ -150,6 +150,12 @@ public:
     //! or contents.
     virtual bool findBlock(const uint256& hash, const FoundBlock& block={}) = 0;
 
+    //! Return whether block descends from a specified ancestor, and
+    //! optionally return ancestor information.
+    virtual bool findAncestorByHash(const uint256& block_hash,
+        const uint256& ancestor_hash,
+        const FoundBlock& ancestor_out={}) = 0;
+
     //! Look up unspent output information. Returns coins in the mempool and in
     //! the current chain UTXO set. Iterates through all the keys in the map and
     //! populates the values.

src/test/interfaces_tests.cpp

@@ -44,4 +44,14 @@ BOOST_AUTO_TEST_CASE(findBlock)
     BOOST_CHECK(!chain->findBlock({}, FoundBlock()));
 }
 
+BOOST_AUTO_TEST_CASE(findAncestorByHash)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+    int height = -1;
+    BOOST_CHECK(chain->findAncestorByHash(active[20]->GetBlockHash(), active[10]->GetBlockHash(), FoundBlock().height(height)));
+    BOOST_CHECK_EQUAL(height, 10);
+    BOOST_CHECK(!chain->findAncestorByHash(active[10]->GetBlockHash(), active[20]->GetBlockHash()));
+}
+
 BOOST_AUTO_TEST_SUITE_END()

src/wallet/rpcdump.cpp

@@ -28,6 +28,8 @@
 
 
 
+using interfaces::FoundBlock;
+
 std::string static EncodeDumpString(const std::string &str) {
     std::stringstream ret;
     for (const unsigned char c : str) {
@@ -359,8 +361,9 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
     }
 
     auto locked_chain = pwallet->chain().lock();
-    Optional<int> height = locked_chain->getBlockHeight(merkleBlock.header.GetHash());
-    if (height == nullopt) {
+    LOCK(pwallet->cs_wallet);
+    int height;
+    if (!pwallet->chain().findAncestorByHash(pwallet->GetLastBlockHash(), merkleBlock.header.GetHash(), FoundBlock().height(height))) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
     }
 
@@ -371,11 +374,9 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
 
     unsigned int txnIndex = vIndex[it - vMatch.begin()];
 
-    CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, *height, merkleBlock.header.GetHash(), txnIndex);
+    CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, height, merkleBlock.header.GetHash(), txnIndex);
     wtx.m_confirm = confirm;
 
-    LOCK(pwallet->cs_wallet);
-
     if (pwallet->IsMine(*wtx.tx)) {
         pwallet->AddToWallet(wtx, false);
         return NullUniValue;