fixed issue #7834 (#7845)

CHANGELOG

@@ -1,3 +1,9 @@
+v3.4.2 (XXXX-XX-XX)
+-------------------
+
+* fixed issue #7834: AQL Query crashes instance
+
+
 v3.4.1 (2018-12-19)
 -------------------
 

arangod/Aql/Scopes.cpp

@@ -191,19 +191,8 @@ void Scopes::addVariable(Variable* variable) {
 void Scopes::replaceVariable(Variable* variable) {
   TRI_ASSERT(!_activeScopes.empty());
   TRI_ASSERT(variable != nullptr);
-
+      
-  for (auto it = _activeScopes.rbegin(); it != _activeScopes.rend(); ++it) {
+  _activeScopes.back()->addVariable(variable);
-    auto scope = (*it);
-
-    if (scope->existsVariable(variable->name)) {
-      // replace existing variable
-      scope->addVariable(variable);
-      return;
-    }
-  }
-
-  THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
-                                 "unable to find AQL variable in scopes");
 }
 
 /// @brief checks whether a variable exists in any scope

tests/js/server/aql/aql-modify-noncluster.js

@@ -155,6 +155,15 @@ function ahuacatlModifySuite () {
       c1 = null;
       c2 = null;
     },
+    
+    testVariableScope : function () {
+      let query = "INSERT {value: 1} INTO " + cn1 + " LET id1 = (UPDATE 'foo' WITH {value: 2} IN " + cn2 + ")  RETURN NEW";
+      let result = AQL_EXECUTE(query).json;
+      assertEqual(1, result[0].value);
+      assertEqual(2, c1.count()); 
+      assertEqual(1, c2.count()); 
+      assertEqual(2, c2.document("foo").value);
+    },
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief test subquery