From 8cf54f754dcdd11ffb6ed4c7aa6794d113c849b3 Mon Sep 17 00:00:00 2001
From: Alexander Bantyev <balsoft@balsoft.ru>
Date: Fri, 14 Jan 2022 20:07:47 +0300
Subject: [PATCH] Show build and substitution information when not connected to
 a TTY
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When stderr is not connected to a tty, show "building" and
"substituting" messages, a-la nix-build et al.

Closes https://github.com/NixOS/nix/issues/4402

Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
---
 src/nix/main.cc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/nix/main.cc b/src/nix/main.cc
index fe7469be4..5158c3902 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -270,11 +270,15 @@ void mainWrapped(int argc, char * * argv)
         if (legacy) return legacy(argc, argv);
     }
 
-    verbosity = lvlNotice;
-    settings.verboseBuild = false;
     evalSettings.pureEval = true;
 
     setLogFormat("bar");
+    settings.verboseBuild = false;
+    if (isatty(STDERR_FILENO)) {
+        verbosity = lvlNotice;
+    } else {
+        verbosity = lvlInfo;
+    }
 
     Finally f([] { logger->stop(); });