延迟执行protractor elementArrayFinder.map函数

Question

如果您调用protractor elementArrayFinder的map函数，它将立即搜索DOM以映射这些元素，这与$$的行为不同，后者等待子元素的elementArrayFinder评估，以查找原始元素及其后代。

我需要延迟map函数执行的原因是我想在测试文件外部预定义它，以便进行抽象。我当前的尝试是：

Question.array = function(elementArrayFinder) {

  function delayedPromise(executor) {
    this.executor = executor;
  }

  delayedPromise.prototype.then = function(onFulfilled, onRejected) {
    console.log('locating elements');
    return (new Promise(this.executor)).then(onFulfilled, onRejected);
  };

  return new delayedPromise(function(resolve, reject) {
    elementArrayFinder.map(function(omniTask) {
      return new Question(omniTask);
    }).then(resolve, reject);
  });
};

这个函数之前一直能正常运行，但是今天我重构了测试文件（不是包含这个函数的文件，这个函数很久没有改动过），JavaScript开始出现与这个函数相关的内存问题：

<--- Last few GCs --->

  133580 ms: Mark-sweep 1354.3 (1421.2) -> 1354.3 (1437.2) MB, 2608.1 / 0.0 ms [allocation failure] [GC in old space requested].
  136052 ms: Mark-sweep 1354.3 (1437.2) -> 1354.3 (1437.2) MB, 2471.9 / 0.0 ms [allocation failure] [GC in old space requested].
  138829 ms: Mark-sweep 1354.3 (1437.2) -> 1355.7 (1421.2) MB, 2775.8 / 0.0 ms [last resort gc].
  141436 ms: Mark-sweep 1355.7 (1421.2) -> 1357.0 (1421.2) MB, 2606.6 / 0.0 ms [last resort gc].


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x13c845cfb51 <JS Object>
    1: enqueue [/Users/thasisclaus/omnistack/node_modules/selenium-webdriver/lib/promise.js:~2742] [pc=0x27de9185871b] (this=0x2b9531847931 <an EventEmitter with map 0x17526dabf9e9>,task=0x17b6b944f181 <a Deferred with map 0x17526dac0649>)
    2: addCallback_ [/Users/thasisclaus/omnistack/node_modules/selenium-webdriver/lib/promise.js:~1328] [pc=0x27de919c1a75] (this=0x17b6b944eeb9 <a ManagedPro...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
 1: node::Abort() [/usr/local/bin/node]
 2: node::FatalException(v8::Isolate*, v8::Local<v8::Value>, v8::Local<v8::Message>) [/usr/local/bin/node]
 3: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [/usr/local/bin/node]
 4: v8::internal::Factory::NewFixedArray(int, v8::internal::PretenureFlag) [/usr/local/bin/node]
 5: v8::internal::Handle<v8::internal::TypeFeedbackMetadata> v8::internal::TypeFeedbackMetadata::New<v8::internal::FeedbackVectorSpec>(v8::internal::Isolate*, v8::internal::FeedbackVectorSpec const*) [/usr/local/bin/node]
 6: v8::internal::(anonymous namespace)::EnsureFeedbackVector(v8::internal::CompilationInfo*) [/usr/local/bin/node]
 7: v8::internal::(anonymous namespace)::GenerateBaselineCode(v8::internal::CompilationInfo*) [/usr/local/bin/node]
 8: v8::internal::(anonymous namespace)::GetUnoptimizedCodeCommon(v8::internal::CompilationInfo*) [/usr/local/bin/node]
 9: v8::internal::Compiler::Compile(v8::internal::Handle<v8::internal::JSFunction>, v8::internal::Compiler::ClearExceptionFlag) [/usr/local/bin/node]
10: v8::internal::Accessors::FunctionLengthGetter(v8::Local<v8::Name>, v8::PropertyCallbackInfo<v8::Value> const&) [/usr/local/bin/node]
11: v8::internal::PropertyCallbackArguments::Call(void (*)(v8::Local<v8::Name>, v8::PropertyCallbackInfo<v8::Value> const&), v8::internal::Handle<v8::internal::Name>) [/usr/local/bin/node]
12: v8::internal::Object::GetPropertyWithAccessor(v8::internal::LookupIterator*) [/usr/local/bin/node]
13: v8::internal::Object::GetProperty(v8::internal::LookupIterator*) [/usr/local/bin/node]
14: v8::internal::Builtin_Impl_FunctionPrototypeBind(v8::internal::(anonymous namespace)::BuiltinArguments<(v8::internal::BuiltinExtraArguments)0>, v8::internal::Isolate*) [/usr/local/bin/node]
15: v8::internal::Builtin_FunctionPrototypeBind(int, v8::internal::Object**, v8::internal::Isolate*) [/usr/local/bin/node]
16: 0x27de909092a7
17: 0x27de9185871b
18: 0x27de919c1a75
19: 0x27de919c202c
20: 0x27de912d1b27
21: 0x27de90909895
22: 0x27de912dee53
>> FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
>>  1: node::Abort() [/usr/local/bin/node]
>>  2: node::FatalException(v8::Isolate*, v8::Local<v8::Value>, v8::Local<v8::Message>) [/usr/local/bin/node]
>>  3: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [/usr/local/bin/node]
>>  4: v8::internal::Factory::NewFixedArray(int, v8::internal::PretenureFlag) [/usr/local/bin/node]
>>  5: v8::internal::Handle<v8::internal::TypeFeedbackMetadata> v8::internal::TypeFeedbackMetadata::New<v8::internal::FeedbackVectorSpec>(v8::internal::Isolate*, v8::internal::FeedbackVectorSpec const*) [/usr/local/bin/node]
>>  6: v8::internal::(anonymous namespace)::EnsureFeedbackVector(v8::internal::CompilationInfo*) [/usr/local/bin/node]
>>  7: v8::internal::(anonymous namespace)::GenerateBaselineCode(v8::internal::CompilationInfo*) [/usr/local/bin/node]
>>  8: v8::internal::(anonymous namespace)::GetUnoptimizedCodeCommon(v8::internal::CompilationInfo*) [/usr/local/bin/node]
>>  9: v8::internal::Compiler::Compile(v8::internal::Handle<v8::internal::JSFunction>, v8::internal::Compiler::ClearExceptionFlag) [/usr/local/bin/node]
>> 10: v8::internal::Accessors::FunctionLengthGetter(v8::Local<v8::Name>, v8::PropertyCallbackInfo<v8::Value> const&) [/usr/local/bin/node]
>> 11: v8::internal::PropertyCallbackArguments::Call(void (*)(v8::Local<v8::Name>, v8::PropertyCallbackInfo<v8::Value> const&), v8::internal::Handle<v8::internal::Name>) [/usr/local/bin/node]
>> 12: v8::internal::Object::GetPropertyWithAccessor(v8::internal::LookupIterator*) [/usr/local/bin/node]
>> 13: v8::internal::Object::GetProperty(v8::internal::LookupIterator*) [/usr/local/bin/node]
>> 14: v8::internal::Builtin_Impl_FunctionPrototypeBind(v8::internal::(anonymous namespace)::BuiltinArguments<(v8::internal::BuiltinExtraArguments)0>, v8::internal::Isolate*) [/usr/local/bin/node]
>> 15: v8::internal::Builtin_FunctionPrototypeBind(int, v8::internal::Object**, v8::internal::Isolate*) [/usr/local/bin/node]
>> 16: 0x27de909092a7
>> 17: 0x27de9185871b
>> 18: 0x27de919c1a75
>> 19: 0x27de919c202c
>> 20: 0x27de912d1b27
>> 21: 0x27de90909895
>> 22: 0x27de912dee53

今天我更改的测试文件中的上下文是：

fit('Should have the right number of assignment questions initially', function(done) {
      var done = browserHelper.strictDone(done),
          self = this;

      self.communityQuestions = self.myQuestions = [];

      console.log(self.assignmentQuestions.length, self.communityQuestions.length, self.myQuestions.length)

      assignmentPage.assignmentQuestions.then(function(assignmentQuestions) {
        expect(assignmentQuestions.length).toEqual(self.assignmentQuestions.length);

        assignmentPage.communityQuestionsTab.click();

        assignmentPage.communityQuestions.then(function(communityQuestions) {
          expect(communityQuestions.length).toEqual(self.communityQuestions.length);

          assignmentPage.myQuestionsTab.click();

          assignmentPage.myQuestions.then(function(myQuestions) {
            console.log(myQuestions);

            expect(myQuestions.length).toEqual(self.myQuestions.length);

            done();
          });
        });
      });
    });

我不知道错误实际上是由函数本身引起的还是函数偶然遇到的某些外部变化所致。无论如何，我认为可能有更好的延迟map函数的方法，很可能是通过直接与Protractor的控制流交互。

- Tahsis Claus

---

我们一直在将地图、过滤器和其他东西放入页面对象函数中，以解决类似的情况。 - alecxe

在页面对象文件中，包含返回映射 Promise 的函数，例如 ageObject.getProperty = function() {return pageObject.previouslyDefinedElementArrayFinder.map(/* args */)}， 而不是像这样做： pageObject.property = pageObject.previouslyDefinedElementArrayFinder.map(/* args */)？ - Tahsis Claus

Answer 1

尽管我没有使用地图返回元素（而是返回从元素构造的对象），但我认为这与地图挂起的错误有关：https://github.com/angular/protractor/issues/2227 为了解决这个问题，我只是将我的map更改为reduce并相应地更改传递的函数，这完美地解决了问题。

我非常确定map是较少更新的elementArrayFinder迭代函数之一，因为与reduce和lodash函数不同，map没有最后一个参数作为集合，因此遵循较旧的约定。

- Tahsis Claus