tty: treat empty NO_COLOR same as absent NO_COLOR

PR-URL: #58074
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: aduh95

lib/internal/tty.js

@@ -99,9 +99,9 @@ function warnOnDeactivatedColors(env) {
   if (warned)
     return;
   let name = '';
-  if (env.NODE_DISABLE_COLORS !== undefined)
+  if (env.NODE_DISABLE_COLORS !== undefined && env.NODE_DISABLE_COLORS !== '')
     name = 'NODE_DISABLE_COLORS';
-  if (env.NO_COLOR !== undefined) {
+  if (env.NO_COLOR !== undefined && env.NO_COLOR !== '') {
     if (name !== '') {
       name += "' and '";
     }
@@ -141,9 +141,9 @@ function getColorDepth(env = process.env) {
     }
   }
 
-  if (env.NODE_DISABLE_COLORS !== undefined ||
+  if ((env.NODE_DISABLE_COLORS !== undefined && env.NODE_DISABLE_COLORS !== '') ||
       // See https://no-color.org/
-      env.NO_COLOR !== undefined ||
+      (env.NO_COLOR !== undefined && env.NO_COLOR !== '') ||
       // The "dumb" special terminal, as defined by terminfo, doesn't support
       // ANSI color control codes.
       // See https://invisible-island.net/ncurses/terminfo.ti.html#toc-_Specials

test/pseudo-tty/test-tty-color-support.js

@@ -61,7 +61,13 @@ const writeStream = new WriteStream(fd);
   [{ TERM: 'ansi' }, 4],
   [{ TERM: 'ANSI' }, 4],
   [{ TERM: 'color' }, 4],
+  [{ TERM: 'linux' }, 4],
+  [{ TERM: 'fail' }, 1],
+  [{ TERM: 'color', NO_COLOR: '' }, 4],
+  [{ TERM: 'color', NODE_DISABLE_COLORS: '' }, 4],
   [{ TERM: 'color', NODE_DISABLE_COLORS: '1' }, 1],
+  [{ TERM: 'color', NODE_DISABLE_COLORS: 0 }, 1],
+  [{ TERM: 'color', NODE_DISABLE_COLORS: null }, 1],
   [{ TERM: 'console' }, 4],
   [{ TERM: 'direct' }, 4],
   [{ TERM: 'dumb' }, 1],
@@ -78,7 +84,9 @@ const writeStream = new WriteStream(fd);
   [{ NO_COLOR: '1', FORCE_COLOR: '2' }, 8],
   [{ NODE_DISABLE_COLORS: '1', FORCE_COLOR: '3' }, 24],
   [{ NO_COLOR: '1', COLORTERM: '24bit' }, 1],
-  [{ NO_COLOR: '', COLORTERM: '24bit' }, 1],
+  [{ NO_COLOR: '', COLORTERM: '24bit' }, 24],
+  [{ NO_COLOR: null, COLORTERM: '24bit' }, 1],
+  [{ NO_COLOR: 0, COLORTERM: '24bit' }, 1],
   [{ TMUX: '1', FORCE_COLOR: 0 }, 1],
   [{ NO_COLOR: 'true', FORCE_COLOR: 0, COLORTERM: 'truecolor' }, 1],
   [{ TERM: 'xterm-256color', COLORTERM: 'truecolor' }, 24],