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.

4 files changed, 54 insertions, 31 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 1514c978b8..c3f12f373d 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3332,16 +3332,18 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
         }
     }
 
-    const CBlockIndex* stopBlock = pwallet->ScanForWalletTransactions(pindexStart, pindexStop, reserver, true);
-    if (!stopBlock) {
-        if (pwallet->IsAbortingRescan()) {
-            throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
-        }
-        // if we got a nullptr returned, ScanForWalletTransactions did rescan up to the requested stopindex
+    const CBlockIndex* stopBlock;
+    CWallet::ScanResult result =
+        pwallet->ScanForWalletTransactions(pindexStart, pindexStop, reserver, stopBlock, true);
+    switch (result) {
+    case CWallet::ScanResult::SUCCESS:
         stopBlock = pindexStop ? pindexStop : pChainTip;
-    }
-    else {
+        break;
+    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);
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index c6aac8aad5..dccda1acf1 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/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()
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 0e135d978d..28ee32b128 100644
--- a/src/wallet/wallet.cpp
+++ b/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);
-        if (failedBlock) {
+        const CBlockIndex* 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
- * possible (due to pruning or corruption), returns pointer to the most recent
- * block that could not be scanned.
+ * @param[in] pindexStop if not a nullptr, the scan will stop at this block-index
+ * @param[out] failed_block if FAILURE is returned, will be set to the most
+ *    recent block that could not be scanned, otherwise nullptr
  *
- * If pindexStop is not a nullptr, the scan will stop at the block-index
- * defined by pindexStop
+ * @return ScanResult indicating success or failure of the scan. SUCCESS if
+ * 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());
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index dcd1ee687b..08184bdc22 100644
--- a/src/wallet/wallet.h
+++ b/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);