fix

book/node_modules/nunjucks-do/index.js

@@ -0,0 +1,24 @@
+var vm = require('vm');
+
+module.exports = function(nunjucks) {
+    return function DoExtension(_env) {
+        this.tags = ['do'];
+
+        this.parse = function(parser, nodes, lexer) {
+            var tok = parser.nextToken();
+            var args = parser.parseSignature(null, true);
+            parser.advanceAfterBlockEnd(tok.value);
+            var body = parser.parseUntilBlocks('enddo');
+            parser.advanceAfterBlockEnd();
+
+            return new nodes.CallExtension(this, 'run', args, [body]);
+        };
+
+        this.run = function(context, body) {
+            var js = body();
+
+            vm.runInNewContext(js, context.ctx);
+            return '';
+        };
+    };
+};