Fix infinite loops

packages/app/src/sandbox/eval/transpilers/babel/babel-worker.js

@@ -3,6 +3,7 @@
 import flatten from 'lodash/flatten';
 import dynamicImportPlugin from './plugins/babel-plugin-dynamic-import-node';
 import detective from './plugins/babel-plugin-detective';
+import infiniteLoops from './plugins/babel-plugin-transform-prevent-infinite-loops';
 
 import { buildWorkerError } from '../utils/worker-error-handler';
 import getDependencies from './get-require-statements';
@@ -27,6 +28,10 @@ declare var Babel: {
 
 Babel.registerPlugin('dynamic-import-node', dynamicImportPlugin);
 Babel.registerPlugin('babel-plugin-detective', detective);
+Babel.registerPlugin(
+  'babel-plugin-transform-prevent-infinite-loops',
+  infiniteLoops
+);
 
 self.addEventListener('message', async event => {
   const { code, path, config } = event.data;
@@ -51,6 +56,7 @@ self.addEventListener('message', async event => {
     ...config.plugins,
     'dynamic-import-node',
     ['babel-plugin-detective', { source: true, nodes: true }],
+    'babel-plugin-transform-prevent-infinite-loops',
   ];
 
   const customConfig = {

packages/app/src/sandbox/eval/transpilers/babel/plugins/babel-plugin-transform-prevent-infinite-loops.js

@@ -0,0 +1,52 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ * Copyright (c) 2017, Amjad Masad
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// Based on https://repl.it/site/blog/infinite-loops.
+
+const MAX_ITERATIONS = 5000;
+
+module.exports = ({ types: t, template }) => {
+  // We set a global so that we can later fail the test
+  // even if the error ends up being caught by the code.
+  const buildGuard = template(`
+    if (ITERATOR++ > MAX_ITERATIONS) {
+      global.infiniteLoopError = new RangeError(
+        'Potential infinite loop: exceeded ' +
+        MAX_ITERATIONS +
+        ' iterations.'
+      );
+      throw global.infiniteLoopError;
+    }
+  `);
+
+  return {
+    visitor: {
+      'WhileStatement|ForStatement|DoWhileStatement': (path, file) => {
+        // An iterator that is incremented with each iteration
+        const iterator = path.scope.parent.generateUidIdentifier('loopIt');
+        const iteratorInit = t.numericLiteral(0);
+        path.scope.parent.push({
+          id: iterator,
+          init: iteratorInit,
+        });
+        // If statement and throw error if it matches our criteria
+        const guard = buildGuard({
+          ITERATOR: iterator,
+          MAX_ITERATIONS: t.numericLiteral(MAX_ITERATIONS),
+        });
+        // No block statment e.g. `while (1) 1;`
+        if (!path.get('body').isBlockStatement()) {
+          const statement = path.get('body').node;
+          path.get('body').replaceWith(t.blockStatement([guard, statement]));
+        } else {
+          path.get('body').unshiftContainer('body', guard);
+        }
+      },
+    },
+  };
+};