Auto merge of #2068 - bitcartel:2045_sendmany_fee_zero, r=bitcartel

Closes #2045 by allowing z_sendmany with 0 fee

qa/rpc-tests/wallet_protectcoinbase.py

@@ -140,6 +140,19 @@ class WalletProtectCoinbaseTest (BitcoinTestFramework):
         assert_equal(Decimal(resp["private"]), Decimal('19.9999'))
         assert_equal(Decimal(resp["total"]), Decimal('39.9999'))
 
+        # A custom fee of 0 is okay.  Here the node will send the note value back to itself.
+        recipients = []
+        recipients.append({"address":myzaddr, "amount": Decimal('19.9999')})
+        myopid = self.nodes[0].z_sendmany(myzaddr, recipients, 1, Decimal('0.0'))
+        mytxid = self.wait_and_assert_operationid_status(myopid)
+        self.sync_all()
+        self.nodes[1].generate(1)
+        self.sync_all()
+        resp = self.nodes[0].z_gettotalbalance()
+        assert_equal(Decimal(resp["transparent"]), Decimal('20.0'))
+        assert_equal(Decimal(resp["private"]), Decimal('19.9999'))
+        assert_equal(Decimal(resp["total"]), Decimal('39.9999'))
+
         # convert note to transparent funds
         recipients = []
         recipients.append({"address":mytaddr, "amount":Decimal('10.0')})

src/wallet/asyncrpcoperation_sendmany.cpp

@@ -55,7 +55,7 @@ AsyncRPCOperation_sendmany::AsyncRPCOperation_sendmany(
         Value contextInfo) :
         fromaddress_(fromAddress), t_outputs_(tOutputs), z_outputs_(zOutputs), mindepth_(minDepth), fee_(fee), contextinfo_(contextInfo)
 {
-    assert(fee_ > 0);
+    assert(fee_ >= 0);
 
     if (minDepth < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Minconf cannot be negative");

src/wallet/rpcwallet.cpp

@@ -3385,7 +3385,12 @@ Value z_sendmany(const Array& params, bool fHelp)
     // Fee in Zatoshis, not currency format)
     CAmount nFee = ASYNC_RPC_OPERATION_DEFAULT_MINERS_FEE;
     if (params.size() > 3) {
-        nFee = AmountFromValue( params[3] );
+        if (params[3].get_real() == 0.0) {
+            nFee = 0;
+        } else {
+            nFee = AmountFromValue( params[3] );
+        }
+
         // Check that the user specified fee is sane.
         if (nFee > nTotalOut) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Fee %s is greater than the sum of outputs %s", FormatMoney(nFee), FormatMoney(nTotalOut)));