Simple, backwards compatible RPC multiwallet support.

src/rpc/server.cpp

@@ -213,6 +213,12 @@ std::string CRPCTable::help(const std::string& strCommand, const JSONRPCRequest&
                     std::string firstLetter = category.substr(0,1);
                     boost::to_upper(firstLetter);
                     strRet += "== " + firstLetter + category.substr(1) + " ==\n";
+                    if (category == "wallet") {
+                        strRet += "\nWhen more than one wallet is loaded (multiple -`wallet=filename` options passed\n"
+                                  "to bitcoind), wallet RPCs must be called with an extra named JSON-RPC `wallet`\n"
+                                  "parameter containing the wallet filename to disambiguate which wallet file the\n"
+                                  "RPC is intended for. Failure to specify will result in method disabled errors.\n\n";
+                    }
                 }
             }
             strRet += strHelp + "\n";
@@ -472,6 +478,11 @@ static inline JSONRPCRequest transformNamedArguments(const JSONRPCRequest& in, c
             hole += 1;
         }
     }
+    auto wallet = argsIn.find("wallet");
+    if (wallet != argsIn.end() && wallet->second->isStr()) {
+        out.wallet = wallet->second->getValStr();
+        argsIn.erase(wallet);
+    }
     // If there are still arguments in the argsIn map, this is an error.
     if (!argsIn.empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Unknown named parameter " + argsIn.begin()->first);

src/rpc/server.h

@@ -42,11 +42,25 @@ class JSONRPCRequest
 public:
     UniValue id;
     std::string strMethod;
+    /**
+     * Parameters from JSON-RPC request.
+     * This will be either an object or an array when the JSONRPCRequest object is
+     * originally created and parsed. But it will be transformed into an
+     * array before being passed to the RPC method implementation (using the
+     * list of named arguments provided by the implementation).
+     */
     UniValue params;
     bool fHelp;
     std::string URI;
     std::string authUser;
 
+    /**
+     * Optional wallet name, set for backwards compatibility if the RPC method
+     * was called with a named "wallet" parameter and the RPC method
+     * implementation doesn't handle it itself.
+     */
+    std::string wallet;
+
     JSONRPCRequest() : id(NullUniValue), params(NullUniValue), fHelp(false) {}
     void parse(const UniValue& valRequest);
 };

src/wallet/rpcwallet.cpp

@@ -32,8 +32,15 @@
 
 CWallet *GetWalletForJSONRPCRequest(const JSONRPCRequest& request)
 {
-    // TODO: Some way to access secondary wallets
-    return vpwallets.empty() ? nullptr : vpwallets[0];
+    if (!request.wallet.empty()) {
+        for (const auto& wallet : ::vpwallets) {
+            if (request.wallet == wallet->GetName()) {
+                return wallet;
+            }
+        }
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "Requested wallet does not exist or is not loaded");
+    }
+    return ::vpwallets.size() == 1 || (request.fHelp && ::vpwallets.size() > 0) ? ::vpwallets[0] : nullptr;
 }
 
 std::string HelpRequiringPassphrase(CWallet * const pwallet)

test/functional/multiwallet.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+# Copyright (c) 2017 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test the wallet."""
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import *
+
+class MultiWalletTest(BitcoinTestFramework):
+
+    def __init__(self):
+        super().__init__()
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+        self.extra_args = [['-wallet=w1', '-wallet=w2','-wallet=w3']]
+
+    def setup_network(self):
+        self.nodes = self.start_nodes(1, self.options.tmpdir, self.extra_args[:1])
+
+    def run_test(self):
+        self.nodes[0].generate(nblocks=1, wallet="w1")
+
+        #check default wallet balance
+        assert_raises_jsonrpc(-32601, "Method not found (disabled)", self.nodes[0].getwalletinfo)
+
+        #check w1 wallet balance
+        walletinfo = self.nodes[0].getwalletinfo(wallet="w1")
+        assert_equal(walletinfo['immature_balance'], 50)
+
+        #check w1 wallet balance
+        walletinfo = self.nodes[0].getwalletinfo(wallet="w2")
+        assert_equal(walletinfo['immature_balance'], 0)
+
+        self.nodes[0].generate(nblocks=101, wallet="w1")
+        assert_equal(self.nodes[0].getbalance(wallet="w1"), 100)
+        assert_equal(self.nodes[0].getbalance(wallet="w2"), 0)
+        assert_equal(self.nodes[0].getbalance(wallet="w3"), 0)
+
+        huh=self.nodes[0].getnewaddress(wallet="w2")
+        self.nodes[0].sendtoaddress(address=huh, amount=1, wallet="w1")
+        self.nodes[0].generate(nblocks=1, wallet="w1")
+        assert_equal(self.nodes[0].getbalance(wallet="w2"), 1)
+
+if __name__ == '__main__':
+    MultiWalletTest().main()

test/functional/test_runner.py

@@ -63,6 +63,7 @@
     'segwit.py',
     # vv Tests less than 2m vv
     'wallet.py',
+    'multiwallet.py',
     'wallet-accounts.py',
     'p2p-segwit.py',
     'wallet-dump.py',