tty: stdio properties are undefined inside exec() child

[silverwind]

I'm wondering if this is intentional or a bug:

parent.js

var exec = require("child_process").exec;

exec("iojs child.js", function (err, stdout, stderr) {
  process.stdout.write(stdout);
});

child.js

console.log(process.stdin.isTTY);
console.log(process.stdin.isRaw);
console.log(process.stdin.setRawMode);
console.log(process.stdout.columns);

output:

undefined
undefined
undefined
undefined

ref: sindresorhus/grunt-shell#95 raineorshine/npm-check-updates#119

[thefourtheye]

When the new process is created, the process.stdin is actually a PIPE and it doesn't have isTTY, isRaw and setRawMode defined. We can actually fix them like this, I think

diff --git a/src/node.js b/src/node.js
index af66b17..87121bc 100644
--- a/src/node.js
+++ b/src/node.js
@@ -717,6 +717,12 @@
         stdin._handle.readStop();
       });

+      stdin.isTTY = true;
+      stdin.isRaw = false;
+      stdin.setRawMode = function setRawMode(mode) {
+        throw new Error('Not a Raw device');
+      };
+
       return stdin;
     });

process.stdout object is actually a Socket object, so columns and rows will not make sense in this case.

[silverwind]

Doing this unconditionally worries me a bit. For the isTTY case, I wonder why the code path in tty_wrap.cc that sets it isn't triggered.

[thefourtheye]

The isTTY is set in tty module's ReadStream constructor function. When the new process is created, guessHandleType calls uv_guess_handle with fd as 0 and than returns PIPE, instead of TTY. So, a net.Socket is created and returned. If uv_guess_handle returned TTY, tty.ReadStream would have been invoked, and isTTY and isRaw would be set properly.

[silverwind]

Hmm, I don't see the process.stdin getter invoked at all when accessing these properties, so your patch doesn't seem to change anything. I'm guessing we have to check out ttywrap.

[thefourtheye]

@silverwind Actually, I tested the changes and it is working fine. Shall I submit a PR with the code in this issue as a test?

[silverwind]

Go ahead, it's good to have a PR so we can run CI anyways.

[thefourtheye]

@silverwind I am not making changes for the columns and rows, as they will be undefined anyway.

[silverwind]

I'm primarily after stdin.isTTY, but I wasn't seeing any difference, it looked as if startup.processStdio was never invoked.