Merge branch 'develop' into ximinez/after-is-never-null

- Expand the description in InvariantChecker_PROTOTYPE::visitEntry.
- Add an explicit assertion in "XRPLNotCreated::visitEntry".

include/xrpl/tx/invariants/InvariantCheck.h

@@ -65,9 +65,13 @@ public:
     /**
      * @brief called for each ledger entry in the current transaction.
      *
-     * @param isDelete true if the SLE is being deleted
-     * @param before ledger entry before modification by the transaction
-     * @param after ledger entry after modification by the transaction
+     * @param isDelete true if the SLE is being deleted.
+     * @param before ledger entry before modification by the
+     *  transaction.
+     * @param after ledger entry after modification by the transaction.
+     *  `after` IS NEVER NULL. `isDelete` is the only correct way to check for deletions.
+     *  Check for null defensively, but do not make any logic decisions based on whether `after` is
+     *  set, because it will always be set.
      */
     void
     visitEntry(bool isDelete, SLE::const_ref before, SLE::const_ref after);

src/libxrpl/tx/invariants/InvariantCheck.cpp

@@ -135,24 +135,28 @@ XRPNotCreated::visitEntry(bool isDelete, SLE::const_ref before, SLE::const_ref a
         }
     }
 
-    if (after)
+    if (!after)
     {
-        switch (after->getType())
-        {
-            case ltACCOUNT_ROOT:
-                drops_ += (*after)[sfBalance].xrp().drops();
-                break;
-            case ltPAYCHAN:
-                if (!isDelete)
-                    drops_ += ((*after)[sfAmount] - (*after)[sfBalance]).xrp().drops();
-                break;
-            case ltESCROW:
-                if (!isDelete && isXRP((*after)[sfAmount]))
-                    drops_ += (*after)[sfAmount].xrp().drops();
-                break;
-            default:
-                break;
-        }
+        // LCOV_EXCL_START
+        UNREACHABLE("xrpl::XRPNotCreated::visitEntry : after can't be null");
+        return;
+        // LCOV_EXCL_STOP
+    }
+    switch (after->getType())
+    {
+        case ltACCOUNT_ROOT:
+            drops_ += (*after)[sfBalance].xrp().drops();
+            break;
+        case ltPAYCHAN:
+            if (!isDelete)
+                drops_ += ((*after)[sfAmount] - (*after)[sfBalance]).xrp().drops();
+            break;
+        case ltESCROW:
+            if (!isDelete && isXRP((*after)[sfAmount]))
+                drops_ += (*after)[sfAmount].xrp().drops();
+            break;
+        default:
+            break;
     }
 }