Return a status enum from ScanForWalletTransactions

Return the failed block as an out var.

This clarifies the outcome as the prior return value could
be null due to user abort or failure.

src/qt/test/wallettests.cpp

@@ -146,7 +146,12 @@ void TestGUI()
         auto locked_chain = wallet->chain().lock();
         WalletRescanReserver reserver(wallet.get());
         reserver.reserve();
-        wallet->ScanForWalletTransactions(chainActive.Genesis(), nullptr, reserver, true);
+        const CBlockIndex* const null_block = nullptr;
+        const CBlockIndex* stop_block;
+        QCOMPARE(
+            wallet->ScanForWalletTransactions(chainActive.Genesis(), nullptr, reserver, stop_block, true /* fUpdate */),
+            CWallet::ScanResult::SUCCESS);
+        QCOMPARE(stop_block, null_block);
     }
     wallet->SetBroadcastTransactions(true);
 

src/test/test_bitcoin.h

@@ -15,9 +15,17 @@
 #include <txmempool.h>
 
 #include <memory>
+#include <type_traits>
 
 #include <boost/thread.hpp>
 
+// Enable BOOST_CHECK_EQUAL for enum class types
+template <typename T>
+std::ostream& operator<<(typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream, const T& e)
+{
+    return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
 extern uint256 insecure_rand_seed;
 extern FastRandomContext insecure_rand_ctx;
 

src/wallet/rpcwallet.cpp

@@ -3332,16 +3332,18 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
         }
     }
 
-    const CBlockIndex* stopBlock = pwallet->ScanForWalletTransactions(pindexStart, pindexStop, reserver, true);
+    const CBlockIndex* stopBlock;
-    if (!stopBlock) {
+    CWallet::ScanResult result =
-        if (pwallet->IsAbortingRescan()) {
+        pwallet->ScanForWalletTransactions(pindexStart, pindexStop, reserver, stopBlock, true);
-            throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
+    switch (result) {
-        }
+    case CWallet::ScanResult::SUCCESS:
-        // if we got a nullptr returned, ScanForWalletTransactions did rescan up to the requested stopindex
         stopBlock = pindexStop ? pindexStop : pChainTip;
-    }
+        break;
-    else {
+    case CWallet::ScanResult::FAILURE:
         throw JSONRPCError(RPC_MISC_ERROR, "Rescan failed. Potentially corrupted data files.");
+    case CWallet::ScanResult::USER_ABORT:
+        throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
+        // no default case, so the compiler can warn about missing cases
     }
     UniValue response(UniValue::VOBJ);
     response.pushKV("start_height", pindexStart->nHeight);

src/wallet/test/wallet_tests.cpp

@@ -38,7 +38,7 @@ BOOST_FIXTURE_TEST_CASE(rescan, TestChain100Setup)
     auto chain = interfaces::MakeChain();
 
     // Cap last block file size, and mine new block in a new block file.
-    CBlockIndex* const nullBlock = nullptr;
+    const CBlockIndex* const null_block = nullptr;
     CBlockIndex* oldTip = chainActive.Tip();
     GetBlockFileInfo(oldTip->GetBlockPos().nFile)->nSize = MAX_BLOCKFILE_SIZE;
     CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));
@@ -53,7 +53,9 @@ BOOST_FIXTURE_TEST_CASE(rescan, TestChain100Setup)
         AddKey(wallet, coinbaseKey);
         WalletRescanReserver reserver(&wallet);
         reserver.reserve();
-        BOOST_CHECK_EQUAL(nullBlock, wallet.ScanForWalletTransactions(oldTip, nullptr, reserver));
+        const CBlockIndex* stop_block;
+        BOOST_CHECK_EQUAL(wallet.ScanForWalletTransactions(oldTip, nullptr, reserver, stop_block), CWallet::ScanResult::SUCCESS);
+        BOOST_CHECK_EQUAL(stop_block, null_block);
         BOOST_CHECK_EQUAL(wallet.GetImmatureBalance(), 100 * COIN);
     }
 
@@ -68,7 +70,9 @@ BOOST_FIXTURE_TEST_CASE(rescan, TestChain100Setup)
         AddKey(wallet, coinbaseKey);
         WalletRescanReserver reserver(&wallet);
         reserver.reserve();
-        BOOST_CHECK_EQUAL(oldTip, wallet.ScanForWalletTransactions(oldTip, nullptr, reserver));
+        const CBlockIndex* stop_block;
+        BOOST_CHECK_EQUAL(wallet.ScanForWalletTransactions(oldTip, nullptr, reserver, stop_block), CWallet::ScanResult::FAILURE);
+        BOOST_CHECK_EQUAL(oldTip, stop_block);
         BOOST_CHECK_EQUAL(wallet.GetImmatureBalance(), 50 * COIN);
     }
 
@@ -286,7 +290,10 @@ public:
         AddKey(*wallet, coinbaseKey);
         WalletRescanReserver reserver(wallet.get());
         reserver.reserve();
-        wallet->ScanForWalletTransactions(chainActive.Genesis(), nullptr, reserver);
+        const CBlockIndex* const null_block = nullptr;
+        const CBlockIndex* stop_block;
+        BOOST_CHECK_EQUAL(wallet->ScanForWalletTransactions(chainActive.Genesis(), nullptr, reserver, stop_block), CWallet::ScanResult::SUCCESS);
+        BOOST_CHECK_EQUAL(stop_block, null_block);
     }
 
     ~ListCoinsTestingSetup()

src/wallet/wallet.cpp

@@ -1613,8 +1613,9 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
     }
 
     if (startBlock) {
-        const CBlockIndex* const failedBlock = ScanForWalletTransactions(startBlock, nullptr, reserver, update);
+        const CBlockIndex* failedBlock;
-        if (failedBlock) {
+        // TODO: this should take into account failure by ScanResult::USER_ABORT
+        if (ScanResult::FAILURE == ScanForWalletTransactions(startBlock, nullptr, reserver, failedBlock, update)) {
             return failedBlock->GetBlockTimeMax() + TIMESTAMP_WINDOW + 1;
         }
     }
@@ -1626,18 +1627,20 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
  * from or to us. If fUpdate is true, found transactions that already
  * exist in the wallet will be updated.
  *
- * Returns null if scan was successful. Otherwise, if a complete rescan was not
+ * @param[in] pindexStop if not a nullptr, the scan will stop at this block-index
- * possible (due to pruning or corruption), returns pointer to the most recent
+ * @param[out] failed_block if FAILURE is returned, will be set to the most
- * block that could not be scanned.
+ *    recent block that could not be scanned, otherwise nullptr
  *
- * If pindexStop is not a nullptr, the scan will stop at the block-index
+ * @return ScanResult indicating success or failure of the scan. SUCCESS if
- * defined by pindexStop
+ * scan was successful. FAILURE if a complete rescan was not possible (due to
+ * pruning or corruption). USER_ABORT if the rescan was aborted before it
+ * could complete.
  *
- * Caller needs to make sure pindexStop (and the optional pindexStart) are on
+ * @pre Caller needs to make sure pindexStop (and the optional pindexStart) are on
  * the main chain after to the addition of any new keys you want to detect
  * transactions for.
  */
-const CBlockIndex* CWallet::ScanForWalletTransactions(const CBlockIndex* const pindexStart, const CBlockIndex* const pindexStop, const WalletRescanReserver& reserver, bool fUpdate)
+CWallet::ScanResult CWallet::ScanForWalletTransactions(const CBlockIndex* const pindexStart, const CBlockIndex* const pindexStop, const WalletRescanReserver& reserver, const CBlockIndex*& failed_block, bool fUpdate)
 {
     int64_t nNow = GetTime();
     const CChainParams& chainParams = Params();
@@ -1648,7 +1651,7 @@ const CBlockIndex* CWallet::ScanForWalletTransactions(const CBlockIndex* const p
     }
 
     const CBlockIndex* pindex = pindexStart;
-    const CBlockIndex* ret = nullptr;
+    failed_block = nullptr;
 
     if (pindex) WalletLogPrintf("Rescan started from block %d...\n", pindex->nHeight);
 
@@ -1669,8 +1672,7 @@ const CBlockIndex* CWallet::ScanForWalletTransactions(const CBlockIndex* const p
             }
         }
         double progress_current = progress_begin;
-        while (pindex && !fAbortRescan && !ShutdownRequested())
+        while (pindex && !fAbortRescan && !ShutdownRequested()) {
-        {
             if (pindex->nHeight % 100 == 0 && progress_end - progress_begin > 0.0) {
                 ShowProgress(strprintf("%s " + _("Rescanning..."), GetDisplayName()), std::max(1, std::min(99, (int)((progress_current - progress_begin) / (progress_end - progress_begin) * 100))));
             }
@@ -1686,14 +1688,14 @@ const CBlockIndex* CWallet::ScanForWalletTransactions(const CBlockIndex* const p
                 if (pindex && !chainActive.Contains(pindex)) {
                     // Abort scan if current block is no longer active, to prevent
                     // marking transactions as coming from the wrong block.
-                    ret = pindex;
+                    failed_block = pindex;
                     break;
                 }
                 for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
                     SyncTransaction(block.vtx[posInBlock], pindex, posInBlock, fUpdate);
                 }
             } else {
-                ret = pindex;
+                failed_block = pindex;
             }
             if (pindex == pindexStop) {
                 break;
@@ -1709,14 +1711,20 @@ const CBlockIndex* CWallet::ScanForWalletTransactions(const CBlockIndex* const p
                 }
             }
         }
+        ShowProgress(strprintf("%s " + _("Rescanning..."), GetDisplayName()), 100); // hide progress dialog in GUI
         if (pindex && fAbortRescan) {
             WalletLogPrintf("Rescan aborted at block %d. Progress=%f\n", pindex->nHeight, progress_current);
+            return ScanResult::USER_ABORT;
         } else if (pindex && ShutdownRequested()) {
             WalletLogPrintf("Rescan interrupted by shutdown request at block %d. Progress=%f\n", pindex->nHeight, progress_current);
+            return ScanResult::USER_ABORT;
         }
-        ShowProgress(strprintf("%s " + _("Rescanning..."), GetDisplayName()), 100); // hide progress dialog in GUI
     }
-    return ret;
+    if (failed_block) {
+        return ScanResult::FAILURE;
+    } else {
+        return ScanResult::SUCCESS;
+    }
 }
 
 void CWallet::ReacceptWalletTransactions()
@@ -4166,11 +4174,11 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
         nStart = GetTimeMillis();
         {
             WalletRescanReserver reserver(walletInstance.get());
-            if (!reserver.reserve()) {
+            const CBlockIndex* stop_block;
+            if (!reserver.reserve() || (ScanResult::SUCCESS != walletInstance->ScanForWalletTransactions(pindexRescan, nullptr, reserver, stop_block, true))) {
                 InitError(_("Failed to rescan the wallet during initialization"));
                 return nullptr;
             }
-            walletInstance->ScanForWalletTransactions(pindexRescan, nullptr, reserver, true);
         }
         walletInstance->WalletLogPrintf("Rescan completed in %15dms\n", GetTimeMillis() - nStart);
         walletInstance->ChainStateFlushed(chainActive.GetLocator());

src/wallet/wallet.h

@@ -896,7 +896,13 @@ public:
     void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex *pindex, const std::vector<CTransactionRef>& vtxConflicted) override;
     void BlockDisconnected(const std::shared_ptr<const CBlock>& pblock) override;
     int64_t RescanFromTime(int64_t startTime, const WalletRescanReserver& reserver, bool update);
-    const CBlockIndex* ScanForWalletTransactions(const CBlockIndex* const pindexStart, const CBlockIndex* const pindexStop, const WalletRescanReserver& reserver, bool fUpdate = false);
+
+    enum class ScanResult {
+        SUCCESS,
+        FAILURE,
+        USER_ABORT
+    };
+    ScanResult ScanForWalletTransactions(const CBlockIndex* const pindexStart, const CBlockIndex* const pindexStop, const WalletRescanReserver& reserver, const CBlockIndex*& failed_block, bool fUpdate = false);
     void TransactionRemovedFromMempool(const CTransactionRef &ptx) override;
     void ReacceptWalletTransactions();
     void ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman) override EXCLUSIVE_LOCKS_REQUIRED(cs_main);