From 2c8ab81db7ded83a53619aebf7338ea79c543732 Mon Sep 17 00:00:00 2001
From: Erik Luo <luoe@chromium.org>
Date: Tue, 1 May 2018 19:26:52 +0000
Subject: [PATCH] DevTools: use autocomplete's possibleSideEffect to bypass
 throwOnSideEffect

Allow Console to evaluate without throwOnSideEffect when the entire
expression meets the same strict conditions used by JSAutocomplete.

Bug: 810176
Change-Id: If5c80250cd75d81eec1e495d0414903213fac930
Reviewed-on: https://chromium-review.googlesource.com/1028934
Commit-Queue: Erik Luo <luoe@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Joel Einbinder <einbinder@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#555142}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: fcaafdd756b1aef4f8244474e37be9ee12c75284
---
 front_end/console/ConsolePrompt.js            |  5 ++-
 front_end/formatter/FormatterWorkerPool.js    | 10 +++++-
 front_end/formatter_worker/FormatterWorker.js | 35 +++++++++++++++++--
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/front_end/console/ConsolePrompt.js b/front_end/console/ConsolePrompt.js
index 7cfeff4a84..b8ea650cff 100644
--- a/front_end/console/ConsolePrompt.js
+++ b/front_end/console/ConsolePrompt.js
@@ -81,11 +81,14 @@ Console.ConsolePrompt = class extends UI.Widget {
       return;
     }
 
+    // Checking for possible side effects uses the same logic as JavaScriptAutocomplete.
+    // This grows the set of previewable expressions without whitelisting.
+    const hasPossibleSideEffects = await Formatter.formatterWorkerPool().hasPossibleSideEffects(text);
     const options = {
       expression: SDK.RuntimeModel.wrapObjectLiteralExpressionIfNeeded(text),
       includeCommandLineAPI: true,
       generatePreview: true,
-      throwOnSideEffect: true,
+      throwOnSideEffect: hasPossibleSideEffects,
       timeout: 500
     };
     const result = await executionContext.evaluate(options, true /* userGesture */, false /* awaitPromise */);
diff --git a/front_end/formatter/FormatterWorkerPool.js b/front_end/formatter/FormatterWorkerPool.js
index 6890f5073d..94a28f2367 100644
--- a/front_end/formatter/FormatterWorkerPool.js
+++ b/front_end/formatter/FormatterWorkerPool.js
@@ -49,7 +49,7 @@ Formatter.FormatterWorkerPool = class {
 
     this._workerTasks.set(worker, null);
     this._processNextTask();
-    task.callback(event.data ? event.data : null);
+    task.callback(event.data);
   }
 
   /**
@@ -239,6 +239,14 @@ Formatter.FormatterWorkerPool = class {
     return /** @type {!Promise<?{baseExpression: string, possibleSideEffects:boolean}>} */ (
         this._runTask('findLastExpression', {content}));
   }
+
+  /**
+   * @param {string} content
+   * @return {!Promise<boolean>}
+   */
+  hasPossibleSideEffects(content) {
+    return /** @type {!Promise<boolean>} */ (this._runTask('hasPossibleSideEffects', {content}));
+  }
 };
 
 Formatter.FormatterWorkerPool.MaxWorkers = 2;
diff --git a/front_end/formatter_worker/FormatterWorker.js b/front_end/formatter_worker/FormatterWorker.js
index 791c5a8162..60d9e346e9 100644
--- a/front_end/formatter_worker/FormatterWorker.js
+++ b/front_end/formatter_worker/FormatterWorker.js
@@ -87,6 +87,9 @@ self.onmessage = function(event) {
     case 'findLastExpression':
       postMessage(FormatterWorker.findLastExpression(params.content));
       break;
+    case 'hasPossibleSideEffects':
+      postMessage(FormatterWorker.hasPossibleSideEffects(params.content));
+      break;
     default:
       console.error('Unsupport method name: ' + method);
   }
@@ -371,9 +374,18 @@ FormatterWorker.findLastExpression = function(content) {
   let baseExpression = parsedContent.substring(baseNode.start, parsedContent.length - suffix.length);
   if (baseExpression.startsWith('{'))
     baseExpression = `(${baseExpression})`;
+  const possibleSideEffects = FormatterWorker._possibleSideEffects(/** @type {!ESTree.Node} */ (baseNode));
+  return {baseExpression, possibleSideEffects};
+};
+
+/**
+ * @param {!ESTree.Node} node
+ * @return {boolean}
+ */
+FormatterWorker._possibleSideEffects = function(node) {
   const sideEffectFreeTypes = new Set([
     'MemberExpression', 'Identifier', 'BinaryExpression', 'Literal', 'TemplateLiteral', 'TemplateElement',
-    'ObjectExpression', 'ArrayExpression', 'Property', 'ThisExpression'
+    'ObjectExpression', 'ArrayExpression', 'Property', 'ThisExpression', 'Program', 'ExpressionStatement'
   ]);
   let possibleSideEffects = false;
   const sideEffectwalker = new FormatterWorker.ESTreeWalker(node => {
@@ -382,8 +394,25 @@ FormatterWorker.findLastExpression = function(content) {
     if (possibleSideEffects)
       return FormatterWorker.ESTreeWalker.SkipSubtree;
   });
-  sideEffectwalker.walk(/** @type {!ESTree.Node} */ (baseNode));
-  return {baseExpression, possibleSideEffects};
+  sideEffectwalker.walk(node);
+  return possibleSideEffects;
+};
+
+/**
+ * @param {string} text
+ * @return {boolean}
+ */
+FormatterWorker.hasPossibleSideEffects = function(text) {
+  if (text.length > 10000)
+    return true;
+  let ast = null;
+  try {
+    ast = acorn.parse(text, {ecmaVersion: 9});
+  } catch (e) {
+  }
+  if (!ast)
+    return true;
+  return FormatterWorker._possibleSideEffects(ast);
 };
 
 /**