tty: do not end in an infinite warning recursion

It was possible that this warning ends up in an infinite recursion.
The reason is that printing the warning triggered a color check and
that triggered another warning. Limiting it to a single warning
prevents this.

PR-URL: #31429
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/internal/tty.js

@@ -73,18 +73,26 @@ const TERM_ENVS_REG_EXP = [
   /^vt100/
 ];
 
+let warned = false;
 function warnOnDeactivatedColors(env) {
-  let name;
+  if (warned)
+    return;
+  let name = '';
   if (env.NODE_DISABLE_COLORS !== undefined)
     name = 'NODE_DISABLE_COLORS';
-  if (env.NO_COLOR !== undefined)
-    name = 'NO_COLOR';
+  if (env.NO_COLOR !== undefined) {
+    if (name !== '') {
+      name += "' and '";
+    }
+    name += 'NO_COLOR';
+  }
 
-  if (name !== undefined) {
+  if (name !== '') {
     process.emitWarning(
       `The '${name}' env is ignored due to the 'FORCE_COLOR' env being set.`,
       'Warning'
     );
+    warned = true;
   }
 }
 

test/pseudo-tty/test-tty-color-support-warning-2.js

@@ -0,0 +1,8 @@
+'use strict';
+
+require('../common');
+
+process.env.NODE_DISABLE_COLORS = '1';
+process.env.FORCE_COLOR = '3';
+
+console.log();

test/pseudo-tty/test-tty-color-support-warning-2.out

@@ -0,0 +1,2 @@
+
+(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.

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

@@ -0,0 +1,9 @@
+'use strict';
+
+require('../common');
+
+process.env.NO_COLOR = '1';
+process.env.NODE_DISABLE_COLORS = '1';
+process.env.FORCE_COLOR = '3';
+
+console.log();

test/pseudo-tty/test-tty-color-support-warning.out

@@ -0,0 +1,2 @@
+
+(node:*) Warning: The 'NODE_DISABLE_COLORS' and 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.

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

@@ -1,8 +1 @@
 (node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NO_COLOR' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.
-(node:*) Warning: The 'NODE_DISABLE_COLORS' env is ignored due to the 'FORCE_COLOR' env being set.