tty: add attribution for chalk

This adds attributions for the getColorDepth function as it got
inspired by https://github.com/chalk/supports-color and more sources.

PR-URL: https://github.com/nodejs/node/pull/19730
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

2 files changed, 106 insertions, 72 deletions

diff --git a/lib/internal/tty.js b/lib/internal/tty.js
new file mode 100644
index 0000000000..a581ac312f
--- /dev/null
+++ b/lib/internal/tty.js
@@ -0,0 +1,104 @@
+// MIT License
+
+// Copyright (c) Sindre Sorhus <sindresorhus@gmail.com> (sindresorhus.com)
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+'use strict';
+
+const { release } = require('os');
+
+const OSRelease = release().split('.');
+
+const COLORS_2 = 1;
+const COLORS_16 = 4;
+const COLORS_256 = 8;
+const COLORS_16m = 24;
+
+// The `getColorDepth` API got inspired by multiple sources such as
+// https://github.com/chalk/supports-color,
+// https://github.com/isaacs/color-support.
+function getColorDepth(env = process.env) {
+  if (env.NODE_DISABLE_COLORS || env.TERM === 'dumb' && !env.COLORTERM) {
+    return COLORS_2;
+  }
+
+  if (process.platform === 'win32') {
+    // Windows 10 build 10586 is the first Windows release that supports 256
+    // colors. Windows 10 build 14931 is the first release that supports
+    // 16m/TrueColor.
+    if (+OSRelease[0] >= 10) {
+      const build = +OSRelease[2];
+      if (build >= 14931)
+        return COLORS_16m;
+      if (build >= 10586)
+        return COLORS_256;
+    }
+
+    return COLORS_16;
+  }
+
+  if (env.TMUX) {
+    return COLORS_256;
+  }
+
+  if (env.CI) {
+    if ('TRAVIS' in env || 'CIRCLECI' in env || 'APPVEYOR' in env ||
+      'GITLAB_CI' in env || env.CI_NAME === 'codeship') {
+      return COLORS_256;
+    }
+    return COLORS_2;
+  }
+
+  if ('TEAMCITY_VERSION' in env) {
+    return /^(9\.(0*[1-9]\d*)\.|\d{2,}\.)/.test(env.TEAMCITY_VERSION) ?
+      COLORS_16 : COLORS_2;
+  }
+
+  switch (env.TERM_PROGRAM) {
+    case 'iTerm.app':
+      if (!env.TERM_PROGRAM_VERSION ||
+        /^[0-2]\./.test(env.TERM_PROGRAM_VERSION)) {
+        return COLORS_256;
+      }
+      return COLORS_16m;
+    case 'HyperTerm':
+    case 'Hyper':
+    case 'MacTerm':
+      return COLORS_16m;
+    case 'Apple_Terminal':
+      return COLORS_256;
+  }
+
+  if (env.TERM) {
+    if (/^xterm-256/.test(env.TERM))
+      return COLORS_256;
+    if (/^screen|^xterm|^vt100|color|ansi|cygwin|linux/i.test(env.TERM))
+      return COLORS_16;
+  }
+
+  if (env.COLORTERM)
+    return COLORS_16;
+
+  return COLORS_2;
+}
+
+module.exports = {
+  getColorDepth
+};
diff --git a/lib/tty.js b/lib/tty.js
index 51ec1cf898..dfb76bbe53 100644
--- a/lib/tty.js
+++ b/lib/tty.js
@@ -27,14 +27,7 @@ const { TTY, isTTY } = process.binding('tty_wrap');
 const errors = require('internal/errors');
 const { ERR_INVALID_FD } = errors.codes;
 const readline = require('readline');
-const { release } = require('os');
-
-const OSRelease = release().split('.');
-
-const COLORS_2 = 1;
-const COLORS_16 = 4;
-const COLORS_256 = 8;
-const COLORS_16m = 24;
+const { getColorDepth } = require('internal/tty');
 
 function isatty(fd) {
   return Number.isInteger(fd) && fd >= 0 && isTTY(fd);
@@ -108,70 +101,7 @@ inherits(WriteStream, net.Socket);
 
 WriteStream.prototype.isTTY = true;
 
-WriteStream.prototype.getColorDepth = function(env = process.env) {
-  if (env.NODE_DISABLE_COLORS || env.TERM === 'dumb' && !env.COLORTERM) {
-    return COLORS_2;
-  }
-
-  if (process.platform === 'win32') {
-    // Windows 10 build 10586 is the first Windows release that supports 256
-    // colors. Windows 10 build 14931 is the first release that supports
-    // 16m/TrueColor.
-    if (+OSRelease[0] >= 10) {
-      const build = +OSRelease[2];
-      if (build >= 14931)
-        return COLORS_16m;
-      if (build >= 10586)
-        return COLORS_256;
-    }
-
-    return COLORS_16;
-  }
-
-  if (env.TMUX) {
-    return COLORS_256;
-  }
-
-  if (env.CI) {
-    if ('TRAVIS' in env || 'CIRCLECI' in env || 'APPVEYOR' in env ||
-      'GITLAB_CI' in env || env.CI_NAME === 'codeship') {
-      return COLORS_256;
-    }
-    return COLORS_2;
-  }
-
-  if ('TEAMCITY_VERSION' in env) {
-    return /^(9\.(0*[1-9]\d*)\.|\d{2,}\.)/.test(env.TEAMCITY_VERSION) ?
-      COLORS_16 : COLORS_2;
-  }
-
-  switch (env.TERM_PROGRAM) {
-    case 'iTerm.app':
-      if (!env.TERM_PROGRAM_VERSION ||
-        /^[0-2]\./.test(env.TERM_PROGRAM_VERSION)) {
-        return COLORS_256;
-      }
-      return COLORS_16m;
-    case 'HyperTerm':
-    case 'Hyper':
-    case 'MacTerm':
-      return COLORS_16m;
-    case 'Apple_Terminal':
-      return COLORS_256;
-  }
-
-  if (env.TERM) {
-    if (/^xterm-256/.test(env.TERM))
-      return COLORS_256;
-    if (/^screen|^xterm|^vt100|color|ansi|cygwin|linux/i.test(env.TERM))
-      return COLORS_16;
-  }
-
-  if (env.COLORTERM)
-    return COLORS_16;
-
-  return COLORS_2;
-};
+WriteStream.prototype.getColorDepth = getColorDepth;
 
 WriteStream.prototype._refreshSize = function() {
   const oldCols = this.columns;