为什么我会得到“任务完成回调太多次”在吞咽？ [英] Why might I be getting "task completion callback called too many times" in gulp?

问题描述

$ b

错误：任务完成回调调用次数太多

 函数myTask（options，cb）{// cb是吞噬cb 
 var serverInstance = http.createServer（dispatch（{/ * routes * /}））; 
 
 serverInstance.listen（options.port，function（）{
 cb（）; //堆栈跟踪标识此行为抛出错误
}）; 
 
 
函数partial（fn）{
 var args = Array.prototype.slice.call（arguments，1）; 
 
 return function（）{
 return fn.apply（this，args.concat（Array.prototype.slice.call（arguments）））; 
}; 
} 
 
 gulp.task（'task-name'，['task-dependency']，partial（myTask，{port：8080}））; 
  

编辑：

  gulp.task（'task-name' ，['task-dependency']，function（cb）{
 partial（myTask，{port：8080}）（cb）; 
}）; 
  

解决方案

这是因为gulp使用启发式（包括返回值的回调以及它是否接受回调参数）来检测异步与同步任务，并且相应地对它们进行不同的处理。我的部分函数返回一个没有声明参数的函数，它会欺骗吞咽者，认为它是异步时同步的。

修改 partial c $ c>返回带有单个命名参数的函数解决了这个问题。

  // ... 
返回函数（cb）{
返回fn.apply（this，args.concat（slice.call（arguments）））; 
}; 
 // ... 
  




Given the following gulp task, why might I be getting the following error?

Error: task completion callback called too many times

function myTask(options, cb) { // cb is the gulp cb
  var serverInstance = http.createServer(dispatch({ /*routes*/ }));

  serverInstance.listen(options.port, function() {
    cb(); // Stack trace identifies this line as throwing the error
  });
}

function partial(fn) {   
    var args = Array.prototype.slice.call(arguments, 1);

    return function() {
        return fn.apply(this, args.concat(Array.prototype.slice.call(arguments)));
    };
}

gulp.task('task-name', ['task-dependency'], partial(myTask, { port: 8080 }));

Edit:

The following modification makes it work (my question still remains however):

gulp.task('task-name', ['task-dependency'], function(cb) {
  partial(myTask, { port: 8080 })(cb);
});

解决方案

This is because gulp uses heuristics (including the return value of the callback and whether it accepts a callback parameter) to detect async vs sync tasks, and it treats them differently accordingly. My partial function returns a function with no parameters declared that was tricking gulp into thinking it was synchronous when it was asynchronous.

Modifying partial to return a function with a single named parameter solved the issue.

//...
return function(cb) {
  return fn.apply(this, args.concat(slice.call(arguments)));
};
//...

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