From 6c8d6be6b5b4fc38a3efd9b3ebf9e813c2546d19 Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <145775305+xokdvium@users.noreply.github.com>
Date: Fri, 29 Nov 2024 23:02:37 +0300
Subject: [PATCH] fix(libutil/terminal): require both stderr/stdout to be tty
 to output color

This is a bit more conservative and safe for cli composability. A common use-case
for nix cli is to filter/transform output with grep/ripgrep/jq from stdout. Those
tools usually have their own colored output. It's best not to step on their toes.

Once example of such command is: `nix registry list | rg nixpkgs`

Note that this is more of a band-aid solution. Nix generally handles ANSI colors
in an ad-hoc way and there might be some other unexpected bugs related to control
characters.
---
 src/libutil/terminal.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libutil/terminal.cc b/src/libutil/terminal.cc
index 4c127ddb078..8b773eaad8c 100644
--- a/src/libutil/terminal.cc
+++ b/src/libutil/terminal.cc
@@ -18,6 +18,7 @@ bool isTTY()
 {
     static const bool tty =
         isatty(STDERR_FILENO)
+        && isatty(STDOUT_FILENO)
         && getEnv("TERM").value_or("dumb") != "dumb"
         && !(getEnv("NO_COLOR").has_value() || getEnv("NOCOLOR").has_value());