fix: assignment should calculate the right side first, close #12

axetroy · May 17, 2018 · 5bdcbdf · 5bdcbdf
1 parent 67d1dd7
commit 5bdcbdf
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Showing 2 changed files with 23 additions and 1 deletion.
diff --git a/src/evaluate.ts b/src/evaluate.ts
@@ -1101,6 +1101,8 @@ const visitors: EvaluateMap = {
   AssignmentExpression(path) {
     const { node, scope } = path;
     let $var: IVar;
+    // right first
+    const rightValue = evaluate(path.createChild(node.right));
 
     if (isIdentifier(node.left)) {
       const { name } = node.left;
@@ -1203,7 +1205,7 @@ const visitors: EvaluateMap = {
         $var.set($var.value & v);
         return $var.value;
       }
-    }[node.operator](evaluate(path.createChild(node.right)));
+    }[node.operator](rightValue);
   },
   LogicalExpression(path) {
     const { node } = path;

diff --git a/test/common/assignment.test.ts b/test/common/assignment.test.ts
@@ -0,0 +1,20 @@
+import test from "ava";
+import vm from "../../src/vm";
+
+test("Assignment should calculate the right expression first", t => {
+  const sandbox: any = vm.createContext({});
+
+  try {
+    vm.runInContext(
+      `
+const a = 123;
+
+a = b
+      `,
+      sandbox
+    );
+    t.fail("it should throw an error");
+  } catch (err) {
+    t.deepEqual(err.message, "b is not defined");
+  }
+});