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http: DRY ClientRequest.prototype._deferToConnect #2769

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http: DRY ClientRequest.prototype._deferToConnect #2769

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http: DRY ClientRequest.prototype._deferToConnect
ahoym Sep 9, 2015
66ddd88
Prefer fn declaration and braceless if statements
ahoym Sep 9, 2015
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Remove unnecessary semi-colon
ahoym Sep 9, 2015
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18 changes: 8 additions & 10 deletions lib/_http_client.js
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Original file line number Diff line number Diff line change
Expand Up @@ -504,19 +504,17 @@ ClientRequest.prototype._deferToConnect = function(method, arguments_, cb) {
// in the future (when a socket gets assigned out of the pool and is
// eventually writable).
var self = this;
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While you're here, self doesn't seem to be necessary. Mind removing it? It can be replaced with, as far as I can tell, a var socket = this.socket. The bottom reference to self can just be used as this.

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I converted the code as you suggested (good catch btw), and that caused the error

cannot read property 'writable' of null

if (socket.writable) { // socket used to be self.socket
  ...

This seems to stem from the initial _deferToConnect call, where this.socket is undefined. When the ClientRequest catches the 'socket' event, the socket variable in onSocket() refers to the initial undefined value which was scoped in. As a result, everything blows up when trying to read the writable property of that.

A work around that I found was to have onSocket() accept a sock argument (given by the socket event), and update socket with that parameter. So this piece of code works:

ClientRequest.prototype._deferToConnect = function(method, arguments_, cb) {
  // ...
  var socket = this.socket;
  function callSocketMethod() {
    if (method)
      socket[method].apply(socket, arguments_);
    if (typeof cb === 'function')
      cb();
  }
  var onSocket = function(sock) { // Now accepts the socket from the 'socket' event.
    socket = sock || socket; // Update socket reference.
    if (socket.writable) {
      callSocketMethod();
    } else {
      socket.once('connect', callSocketMethod);
    }
  };
  if (!socket) {
    this.once('socket', onSocket);
  } else {
    onSocket();
  }
};

However I'm not completely sure on the repercussions of this. Maybe leaving the existing implementation would be for the better? I'm interested in what you think

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Hmm, you're right, that is something I missed originally. I'd say let's keep the current implementation, as that new one wouldn't really improve the quality of the code. Sorry about the run around!

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Sounds good, then I'll leave this PR as it is. And no need to apologize, we got some documentation and a deeper understanding of the code here 😄

var callSocketMethod = function() {
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Can you make this function callSocketMethod()

if (method) {
self.socket[method].apply(self.socket, arguments_);
}
if (cb) { cb(); }
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if (typeof cb === 'function')
  cb();

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Are the absence of curly braces preferred?

I'm just wondering because I've seen plenty of cases of both in this file, and I'd like to conform to consistency.

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Yes, core prefers to leave out braces in if statements. If there are any else conditions that require braces, then all branches use braces for consistency (not applicable here).

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Cool, good to know.

Then on a similar vein, we should also do this above?

if (method)
  self.socket[method].apply(self.socket, arguments_);

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Ah. Yes :-)

};
var onSocket = function() {
if (self.socket.writable) {
if (method) {
self.socket[method].apply(self.socket, arguments_);
}
if (cb) { cb(); }
callSocketMethod();
} else {
self.socket.once('connect', function() {
if (method) {
self.socket[method].apply(self.socket, arguments_);
}
if (cb) { cb(); }
});
self.socket.once('connect', callSocketMethod);
}
};
if (!self.socket) {
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