lnd+walletunlocker: move history drop to unlocker

Apparently dropping the wallet transaction history only fully takes
effect after opening the wallet from scratch again. To do this cleanly,
we need to do it in the unlocker instead of lnd.

walletunlocker/service.go

@@ -133,11 +133,16 @@ type UnlockerService struct {
 	// dbTimeout specifies the timeout value to use when opening the wallet
 	// database.
 	dbTimeout time.Duration
+
+	// resetWalletTransactions indicates that the wallet state should be
+	// reset on unlock to force a full chain rescan.
+	resetWalletTransactions bool
 }
 
 // New creates and returns a new UnlockerService.
 func New(chainDir string, params *chaincfg.Params, noFreelistSync bool,
-	macaroonFiles []string, dbTimeout time.Duration) *UnlockerService {
+	macaroonFiles []string, dbTimeout time.Duration,
+	resetWalletTransactions bool) *UnlockerService {
 
 	return &UnlockerService{
 		InitMsgs:   make(chan *WalletInitMsg, 1),
@@ -145,12 +150,13 @@ func New(chainDir string, params *chaincfg.Params, noFreelistSync bool,
 
 		// Make sure we buffer the channel is buffered so the main lnd
 		// goroutine isn't blocking on writing to it.
-		MacResponseChan: make(chan []byte, 1),
-		chainDir:        chainDir,
-		netParams:       params,
-		macaroonFiles:   macaroonFiles,
-		dbTimeout:       dbTimeout,
-		noFreelistSync:  noFreelistSync,
+		MacResponseChan:         make(chan []byte, 1),
+		chainDir:                chainDir,
+		netParams:               params,
+		macaroonFiles:           macaroonFiles,
+		dbTimeout:               dbTimeout,
+		noFreelistSync:          noFreelistSync,
+		resetWalletTransactions: resetWalletTransactions,
 	}
 }
 
@@ -400,6 +406,37 @@ func (u *UnlockerService) UnlockWallet(ctx context.Context,
 		return nil, err
 	}
 
+	// The user requested to drop their whole wallet transaction state to
+	// force a full chain rescan for wallet addresses. Dropping the state
+	// only properly takes effect after opening the wallet. That's why we
+	// start, drop, stop and start again.
+	if u.resetWalletTransactions {
+		dropErr := wallet.DropTransactionHistory(
+			unlockedWallet.Database(), true,
+		)
+
+		// Even if dropping the history fails, we'll want to unload the
+		// wallet. If unloading fails, that error is probably more
+		// important to be returned to the user anyway.
+		if err := loader.UnloadWallet(); err != nil {
+			return nil, fmt.Errorf("could not unload "+
+				"wallet (tx history drop err: %v): %v", dropErr,
+				err)
+		}
+
+		// If dropping failed but unloading didn't, we'll still abort
+		// and inform the user.
+		if dropErr != nil {
+			return nil, dropErr
+		}
+
+		// All looks good, let's now open the wallet again.
+		unlockedWallet, err = loader.OpenExistingWallet(password, false)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	// We successfully opened the wallet and pass the instance back to
 	// avoid it needing to be unlocked again.
 	walletUnlockMsg := &WalletUnlockMsg{