Input from TTY is strange

I tried read from STDIN by fs.readSync that is given process.stdin.fd.
For example:

var
  fs = require('fs'),
  buffer = new Buffer(1024),
  fd = process.platform === 'win32' ? process.stdin.fd : fs.openSync('/dev/tty', 'r'),
  readSize = fs.readSync(fd, buffer, 0, 1024);

console.log('INPUT: ' + buffer.toString('utf8', 0, readSize));

In v2.3.1-, no problem:

foo
INPUT: foo

In v2.3.2+, first line is ignored, and second line is accepted:

foo
bar
INPUT: bar

This problem occurs in only Windows + iojs v2.3.2+.
I don't use process.stdin.fd in non-Win because fs.readSync can't read it.
Therefore, process.stdin of v2.3.2+ might have problem. (not fs.readSync)

This is seems to be a regression that could have been introduced by 8cee8f5 (didn't do git bisect, just layman's bisecting). @nodejs/platform-windows ?

If 8cee8f5 made this problem, I think that windows label is not suitably, because I didn't use process.stdin in non-Win. And in case that doesn't use process.stdin (open('CONIN$') instead of it) in Windows is no problem.

From what I can tell it has to do with process.stdin taking so long to initialize when first accessed.

For example, if you use:

process.stdin;
console.log('ready');
var
  fs = require('fs'),
  buffer = new Buffer(1024),
  fd = process.platform === 'win32' ? process.stdin.fd : fs.openSync('/dev/tty', 'r'),
  readSize = fs.readSync(fd, buffer, 0, 1024);

console.log('INPUT: ' + buffer.toString('utf8', 0, readSize));

Then the first line will get read as expected if you type it after ready is displayed.

You can also replace process.stdin.fd in the original code with just 0 and it will get the first line too.

I'm trying this all on Windows, so I haven't looked at it on *nix. Also, reverting 8cee8f5 does not affect this particular issue.

Thank you, but... I tried your solution, and it did not read first line.

ready
foo
bar
INPUT: bar

I tried your sample code on Windows 8.1 64bit with iojs v2.3.1, v2.3.2 and v3.1.0. Of course v2.3.1 works fine.

Also I tried 0 instead of process.stdin.fd. It works fine before accessing to process.stdin, but it doesn't read first line after accessing to process.stdin.

For example, this code doesn't read first line:

var
  fs = require('fs'),
  buffer = new Buffer(1024),
  fd = process.platform === 'win32' ? process.stdin.fd : fs.openSync('/dev/tty', 'r'),
  //readSize = fs.readSync(fd, buffer, 0, 1024);
  readSize = fs.readSync(0, buffer, 0, 1024);

console.log('INPUT: ' + buffer.toString('utf8', 0, readSize));

Yes I know that fd is meaningless now, then this works fine:

var
  fs = require('fs'),
  buffer = new Buffer(1024),
  //fd = process.platform === 'win32' ? process.stdin.fd : fs.openSync('/dev/tty', 'r'),
  //readSize = fs.readSync(fd, buffer, 0, 1024);
  readSize = fs.readSync(0, buffer, 0, 1024);

console.log('INPUT: ' + buffer.toString('utf8', 0, readSize));

But process.stdin might be used at a place I don't know. (e.g. other packages)
That is, this code doesn't read first line:

process.stdin;

var
  fs = require('fs'),
  buffer = new Buffer(1024),
  readSize = fs.readSync(0, buffer, 0, 1024);

console.log('INPUT: ' + buffer.toString('utf8', 0, readSize));

I think that a point is that the programers don't know that process.stdin makes problem, and it should not so. (this is not designed behavior, right?)

@nodejs/streams : is it legal to use fs.readSync to read from process.stdin, which in this case is not a file?

so is the issue that references to process.stdin initiate the readable stream, which does some buffering and that buffering prevents somebody from reading stdin like it was a file?

It seems that programmers use read/readSync with STDIN to get the user's input easily instead of process.stdin.on('data'). Also my module readlineSync tries readSync.
https://www.google.com/search?q=nodejs+read+from+stdin

This problem occurs when it reads from TTY. It seems no problem when it reads from the file or pipe. (e.g. script < file, echo foo | script etc)

It seems that the Readline module also is affected by this problem.

For example:

var readline = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});

readline.question('> ', function(answer) {
  console.log('INPUT: ', answer);
  readline.close();
});

In io.js v2.3.1-, no problem:

> foo
INPUT:  foo

In io.js v2.3.2+, strange second line is shown:

> foo
foo
INPUT:  foo

Node.js v4.2.1 also returns same result:

> foo
foo
INPUT:  foo

It seems that REPL also is affected by this problem.

I typed a first 1 and pushed the Enter key.
In io.js v2.3.1-, no problem:

E:\test>node
> 1
1
>

In io.js v2.3.2+, strange second 1 is shown:

E:\test>node
> 1
1
1
>

Node.js v4.2.1 also returns same result:

E:\test>node
> 1
1
1
>

It seems that only the first line of both readline module and REPL is strange, like readSync.
#2504 (comment)

For example:

> foo
foo
INPUT:  foo
> bar
INPUT:  bar

E:\test>node
> 1
1
1
> 2
2
>

Filed #3490 for the revert. I could use some assistence with a regression test for this.

src: Revert nix stdin _readableState.reading

src: Revert "nix stdin _readableState.reading"

Related to #5384

This issue came again, and it was fixed in v6.2.0.
Then, the versions of Node.js that have the problem:

VERSION >= 2.3.2 && VERSION < 4.2.4
VERSION >= 5.0.0 && VERSION < 5.1.0
VERSION >= 5.6.0 && VERSION < 6.2.0

Easy check:

var verNum = (function(ver) {
    var nums = ver.replace(/^\D+/, '').split('.');
    var verNum = 0;
    if ((nums[0] = +nums[0])) { verNum += nums[0] * 10000; }
    if ((nums[1] = +nums[1])) { verNum += nums[1] * 100; }
    if ((nums[2] = +nums[2])) { verNum += nums[2]; }
    return verNum;
  })(process.version),

  hasProblem =
    verNum >= 20302 && verNum < 40204 ||
    verNum >= 50000 && verNum < 50100 ||
    verNum >= 50600 && verNum < 60200;

if (hasProblem) {
  console.log('TTY has problem.');
} else {
  console.log('TTY has NO problem.');
}

src: Revert "nix stdin _readableState.reading"

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