disable yield var

src/graph/optimizer/rule/TopNRule.cpp

@@ -4,6 +4,7 @@
  */
 
 #include "graph/optimizer/rule/TopNRule.h"
+
 #include "graph/optimizer/OptContext.h"
 #include "graph/optimizer/OptGroup.h"
 #include "graph/planner/plan/PlanNode.h"

src/graph/util/ExpressionUtils.cpp

@@ -63,6 +63,16 @@ std::vector<const Expression *> ExpressionUtils::collectAll(
   return std::move(visitor).results();
 }
 
+bool ExpressionUtils::checkVarExprIfExist(const Expression *expr) {
+  auto vars = ExpressionUtils::collectAll(expr, {Expression::Kind::kVar});
+  for (auto *var : vars) {
+    if (!static_cast<const VariableExpression *>(var)->isInner()) {
+      return true;
+    }
+  }
+  return false;
+}
+
 std::vector<const Expression *> ExpressionUtils::findAllStorage(const Expression *expr) {
   return collectAll(expr,
                     {Expression::Kind::kTagProperty,

src/graph/util/ExpressionUtils.h

@@ -44,6 +44,8 @@ class ExpressionUtils {
   static std::vector<const Expression*> collectAll(
       const Expression* self, const std::unordered_set<Expression::Kind>& expected);
 
+  static bool checkVarExprIfExist(const Expression* expr);
+
   static std::vector<const Expression*> findAllStorage(const Expression* expr);
 
   static std::vector<const Expression*> findAllInputVariableProp(const Expression* expr);

src/parser/parser.yy

@@ -1444,9 +1444,16 @@ yield_column
         delete $3;
     }
     | expression {
+        if (graph::ExpressionUtils::checkVarExprIfExist($1)) {
+            throw nebula::GraphParser::syntax_error(@1, "Direct output of variable is prohibited");
+        }
         $$ = new YieldColumn($1);
     }
     | expression KW_AS name_label {
+        if (graph::ExpressionUtils::checkVarExprIfExist($1)) {
+            delete $3;
+            throw nebula::GraphParser::syntax_error(@1, "Direct output of variable is prohibited");
+        }
         $$ = new YieldColumn($1, *$3);
         delete $3;
     }

tests/tck/features/bugfix/VariableExpression.feature

@@ -0,0 +1,26 @@
+# Copyright (c) 2021 vesoft inc. All rights reserved.
+#
+# This source code is licensed under Apache 2.0 License,
+# attached with Common Clause Condition 1.0, found in the LICENSES directory.
+Feature: Variable usage
+
+  Background:
+    Given a graph with space named "nba"
+
+  Scenario: disable yield $var
+    When executing query:
+      """
+      $var = yield 1;$var2 = yield 3;yield $var1 + $var2
+      """
+    Then a SyntaxError should be raised at runtime: Direct output of variable is prohibited near `$var1 + $var2'
+    When executing query:
+      """
+      $var=go from "Tim Duncan" over like yield like._dst as dst;yield $var
+      """
+    Then a SyntaxError should be raised at runtime: Direct output of variable is prohibited near `$var'
+    Then drop the used space
+    When executing query:
+      """
+      $var=go from "Tim Duncan" over like yield like._dst as dst;yield $var[0][0]
+      """
+    Then a SyntaxError should be raised at runtime: Direct output of variable is prohibited near `$var[0][0]'

tests/tck/features/go/GroupbyLimit.IntVid.feature

@@ -15,7 +15,7 @@ Feature: Groupby & limit Sentence
       """
       GO FROM hash("Marco Belinelli") OVER serve YIELD $$.team.name AS name | GROUP BY $-.start_year YIELD COUNT($var)
       """
-    Then a SemanticError should be raised at runtime:
+    Then a SyntaxError should be raised at runtime:
 
   Scenario: Syntax test4
     When executing query:

tests/tck/features/go/GroupbyLimit.feature

@@ -22,7 +22,7 @@ Feature: Groupby & limit Sentence
       """
       GO FROM "Marco Belinelli" OVER serve YIELD $$.team.name AS name | GROUP BY $-.start_year YIELD COUNT($var)
       """
-    Then a SemanticError should be raised at runtime:
+    Then a SyntaxError should be raised at runtime:
 
   Scenario: Syntax test4
     When executing query: