From 22b6dbaad3915cb2c090ef08ea91d4682c7f65d1 Mon Sep 17 00:00:00 2001
From: Sebastian Malton <smalton@mirantis.com>
Date: Tue, 31 Mar 2020 10:43:36 -0400
Subject: [PATCH 1/2] Set App.ErrWriter in App.Setup()

- Defaults to os.Stderr
- Remove the App.errWriter() function since it is no longer needed
---
 app.go | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/app.go b/app.go
index eb68febbac..9baca251db 100644
--- a/app.go
+++ b/app.go
@@ -163,6 +163,10 @@ func (a *App) Setup() {
 		a.Writer = os.Stdout
 	}
 
+	if a.ErrWriter == nil {
+		a.ErrWriter = os.Stderr
+	}
+
 	var newCommands []*Command
 
 	for _, c := range a.Commands {
@@ -196,10 +200,6 @@ func (a *App) Setup() {
 	if a.Metadata == nil {
 		a.Metadata = make(map[string]interface{})
 	}
-
-	if a.Writer == nil {
-		a.Writer = os.Stdout
-	}
 }
 
 func (a *App) newFlagSet() (*flag.FlagSet, error) {
@@ -326,7 +326,7 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 // code in the cli.ExitCoder
 func (a *App) RunAndExitOnError() {
 	if err := a.Run(os.Args); err != nil {
-		_, _ = fmt.Fprintln(a.errWriter(), err)
+		_, _ = fmt.Fprintln(a.ErrWriter, err)
 		OsExiter(1)
 	}
 }
@@ -480,15 +480,6 @@ func (a *App) VisibleFlags() []Flag {
 	return visibleFlags(a.Flags)
 }
 
-func (a *App) errWriter() io.Writer {
-	// When the app ErrWriter is nil use the package level one.
-	if a.ErrWriter == nil {
-		return ErrWriter
-	}
-
-	return a.ErrWriter
-}
-
 func (a *App) appendFlag(fl Flag) {
 	if !hasFlag(a.Flags, fl) {
 		a.Flags = append(a.Flags, fl)

From fed64f3ad73405c4aa65c8da640d1a8c43667a49 Mon Sep 17 00:00:00 2001
From: Sebastian Malton <smalton@mirantis.com>
Date: Wed, 1 Apr 2020 09:17:59 -0400
Subject: [PATCH 2/2] add tests

---
 app.go      |  1 +
 app_test.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/app.go b/app.go
index 9baca251db..4122596e42 100644
--- a/app.go
+++ b/app.go
@@ -118,6 +118,7 @@ func NewApp() *App {
 		Action:       helpCommand.Action,
 		Compiled:     compileTime(),
 		Writer:       os.Stdout,
+		ErrWriter:    os.Stderr,
 	}
 }
 
diff --git a/app_test.go b/app_test.go
index 61c55d8551..6c95faa612 100644
--- a/app_test.go
+++ b/app_test.go
@@ -2152,3 +2152,34 @@ func newTestApp() *App {
 	a.Writer = ioutil.Discard
 	return a
 }
+
+func TestSetupInitializesBothWriters(t *testing.T) {
+	a := &App{}
+
+	a.Setup()
+
+	if a.ErrWriter != os.Stderr {
+		t.Errorf("expected a.ErrWriter to be os.Stderr")
+	}
+
+	if a.Writer != os.Stdout {
+		t.Errorf("expected a.Writer to be os.Stdout")
+	}
+}
+
+func TestSetupInitializesOnlyNilWriters(t *testing.T) {
+	wr := &bytes.Buffer{}
+	a := &App{
+		ErrWriter: wr,
+	}
+
+	a.Setup()
+
+	if a.ErrWriter != wr {
+		t.Errorf("expected a.ErrWriter to be a *bytes.Buffer instance")
+	}
+
+	if a.Writer != os.Stdout {
+		t.Errorf("expected a.Writer to be os.Stdout")
+	}
+}