fix maximum amt (XRPLF#34)

* fix maximum amt

* add if check to return tecMPT_ISSUANCE_NOT_FOUND

Author: shawnxie999

src/test/app/MPToken_test.cpp

@@ -1015,6 +1015,28 @@ class MPToken_test : public beast::unit_test::suite
             // destroyed, it should fail
             mptAlice.pay(alice, bob, 100, tecMPT_ISSUANCE_NOT_FOUND);
         }
+
+        // Issuers issues maximum amount of MPT to a holder, the holder should
+        // be able to transfer the max amount to someone else
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const carol("bob");
+            Account const bob("carol");
+
+            MPTTester mptAlice(env, alice, {.holders = {&bob, &carol}});
+
+            mptAlice.create(
+                {.maxAmt = 100, .ownerCount = 1, .flags = tfMPTCanTransfer});
+
+            mptAlice.authorize({.account = &bob});
+            mptAlice.authorize({.account = &carol});
+
+            mptAlice.pay(alice, bob, 100);
+
+            // transfer max amount to another holder
+            mptAlice.pay(bob, carol, 100);
+        }
     }
 
     void

src/xrpld/ledger/detail/View.cpp

@@ -1353,6 +1353,20 @@ rippleSend(
 
     if (uSenderID == issuer || uReceiverID == issuer || issuer == noAccount())
     {
+        // if sender is issuer, check that the new OutstandingAmount will not
+        // exceed MaximumAmount
+        if (uSenderID == issuer)
+        {
+            auto const mptID = keylet::mptIssuance(saAmount.issue().getMptID());
+            auto const sle = view.peek(mptID);
+            if (!sle)
+                return tecMPT_ISSUANCE_NOT_FOUND;
+
+            if (sle->getFieldU64(sfOutstandingAmount) + saAmount.value() >
+                (*sle)[~sfMaximumAmount].value_or(maxMPTokenAmount))
+                return tecMPT_MAX_AMOUNT_EXCEEDED;
+        }
+
         // Direct send: redeeming IOUs and/or sending own IOUs.
         auto const ter =
             rippleCredit(view, uSenderID, uReceiverID, saAmount, j);
@@ -1380,8 +1394,8 @@ rippleSend(
                 rippleCredit(view, issuer, uReceiverID, saAmount, j);
             terResult != tesSUCCESS)
             return terResult;
-        else
-            return rippleCredit(view, uSenderID, issuer, saActual, j);
+
+        return rippleCredit(view, uSenderID, issuer, saActual, j);
     }
 
     return tecINTERNAL;
@@ -1872,10 +1886,6 @@ rippleCredit(
                 sfOutstandingAmount,
                 sle->getFieldU64(sfOutstandingAmount) + saAmount.value());
 
-            if (sle->getFieldU64(sfOutstandingAmount) >
-                (*sle)[~sfMaximumAmount].value_or(maxMPTokenAmount))
-                return tecMPT_MAX_AMOUNT_EXCEEDED;
-
             view.update(sle);
         }
         else