From c780bb4626d7c8721ed3b7d441c4020dcfbd939d Mon Sep 17 00:00:00 2001
From: graf0 <grzegorz@marszalek.cc>
Date: Sun, 16 Oct 2022 14:13:23 +0200
Subject: [PATCH] interp: trace should write to stderr by default

Fixes #926.
---
 interp/interp_test.go | 8 ++++++++
 interp/trace.go       | 6 +++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/interp/interp_test.go b/interp/interp_test.go
index a88778cf0..76d22c51e 100644
--- a/interp/interp_test.go
+++ b/interp/interp_test.go
@@ -3130,6 +3130,14 @@ single quote
 	// for trace
 	{
 		`set -x
+exec >/dev/null
+echo "trace should go to stderr"`,
+		`+ exec
++ echo 'trace should go to stderr'
+`,
+	},
+	{
+		`set -x
 animals=(dog, cat, otter)
 for i in ${animals[@]}
 do
diff --git a/interp/trace.go b/interp/trace.go
index 08b6eafce..dbf5087eb 100644
--- a/interp/trace.go
+++ b/interp/trace.go
@@ -14,7 +14,7 @@ import (
 type tracer struct {
 	buf       bytes.Buffer
 	printer   *syntax.Printer
-	stdout    io.Writer
+	output    io.Writer
 	needsPlus bool
 }
 
@@ -25,7 +25,7 @@ func (r *Runner) tracer() *tracer {
 
 	return &tracer{
 		printer:   syntax.NewPrinter(),
-		stdout:    r.stdout,
+		output:    r.stderr,
 		needsPlus: true,
 	}
 }
@@ -74,7 +74,7 @@ func (t *tracer) flush() {
 		return
 	}
 
-	t.stdout.Write(t.buf.Bytes())
+	t.output.Write(t.buf.Bytes())
 	t.buf.Reset()
 }