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tty,doc: add type-check to isatty

Previously, various inputs other than non-negative integers would
produce incorrect results.

Added type-checking on input, returning false for anything other than
non-negative integers.

Also clarified in docs.

PR-URL: #15567
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
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bengl committed Sep 23, 2017
1 parent b5569db commit 27e12e75244343ffcde4b899a31e88d452fa4d6e
Showing with 20 additions and 2 deletions.
  1. +2 −1 doc/api/tty.md
  2. +1 −1 lib/tty.js
  3. +17 −0 test/pseudo-tty/test-tty-isatty.js
  4. 0 test/pseudo-tty/test-tty-isatty.out
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@@ -123,4 +123,5 @@ added: v0.5.8
* `fd` {number} A numeric file descriptor
The `tty.isatty()` method returns `true` if the given `fd` is associated with
a TTY and `false` if is not.
a TTY and `false` if it is not, including whenever `fd` is not a non-negative
integer.
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@@ -30,7 +30,7 @@ const errors = require('internal/errors');
const readline = require('readline');
exports.isatty = function(fd) {
return isTTY(fd);
return Number.isInteger(fd) && fd >= 0 && isTTY(fd);
};
@@ -0,0 +1,17 @@
'use strict';
require('../common');
const { strictEqual } = require('assert');
const { isatty } = require('tty');
strictEqual(isatty(0), true, 'stdin reported to not be a tty, but it is');
strictEqual(isatty(1), true, 'stdout reported to not be a tty, but it is');
strictEqual(isatty(2), true, 'stderr reported to not be a tty, but it is');
strictEqual(isatty(-1), false, '-1 reported to be a tty, but it is not');
strictEqual(isatty(55555), false, '55555 reported to be a tty, but it is not');
strictEqual(isatty(1.1), false, '1.1 reported to be a tty, but it is not');
strictEqual(isatty('1'), false, '\'1\' reported to be a tty, but it is not');
strictEqual(isatty({}), false, '{} reported to be a tty, but it is not');
strictEqual(isatty(() => {}), false,
'() => {} reported to be a tty, but it is not');
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