Write err to stderr, exit 1 if err != ""

Closes #475

app_test.go

@@ -13,6 +13,19 @@ import (
 	"testing"
 )
 
+var (
+	lastExitCode = 0
+	fakeOsExiter = func(rc int) {
+		lastExitCode = rc
+	}
+	fakeErrWriter = &bytes.Buffer{}
+)
+
+func init() {
+	OsExiter = fakeOsExiter
+	ErrWriter = fakeErrWriter
+}
+
 type opCounts struct {
 	Total, BashComplete, OnUsageError, Before, CommandNotFound, Action, After, SubCommand int
 }

errors.go

@@ -88,5 +88,11 @@ func HandleExitCoder(err error) {
 		for _, merr := range multiErr.Errors {
 			HandleExitCoder(merr)
 		}
+		return
+	}
+
+	if err.Error() != "" {
+		fmt.Fprintln(ErrWriter, err)
+		OsExiter(1)
 	}
 }

errors_test.go

@@ -1,8 +1,8 @@
 package cli
 
 import (
+	"bytes"
 	"errors"
-	"os"
 	"testing"
 )
 
@@ -15,7 +15,7 @@ func TestHandleExitCoder_nil(t *testing.T) {
 		called = true
 	}
 
-	defer func() { OsExiter = os.Exit }()
+	defer func() { OsExiter = fakeOsExiter }()
 
 	HandleExitCoder(nil)
 
@@ -32,7 +32,7 @@ func TestHandleExitCoder_ExitCoder(t *testing.T) {
 		called = true
 	}
 
-	defer func() { OsExiter = os.Exit }()
+	defer func() { OsExiter = fakeOsExiter }()
 
 	HandleExitCoder(NewExitError("galactic perimeter breach", 9))
 
@@ -49,7 +49,7 @@ func TestHandleExitCoder_MultiErrorWithExitCoder(t *testing.T) {
 		called = true
 	}
 
-	defer func() { OsExiter = os.Exit }()
+	defer func() { OsExiter = fakeOsExiter }()
 
 	exitErr := NewExitError("galactic perimeter breach", 9)
 	err := NewMultiError(errors.New("wowsa"), errors.New("egad"), exitErr)
@@ -58,3 +58,49 @@ func TestHandleExitCoder_MultiErrorWithExitCoder(t *testing.T) {
 	expect(t, exitCode, 9)
 	expect(t, called, true)
 }
+
+func TestHandleExitCoder_ErrorWithMessage(t *testing.T) {
+	exitCode := 0
+	called := false
+
+	OsExiter = func(rc int) {
+		exitCode = rc
+		called = true
+	}
+	ErrWriter = &bytes.Buffer{}
+
+	defer func() {
+		OsExiter = fakeOsExiter
+		ErrWriter = fakeErrWriter
+	}()
+
+	err := errors.New("gourd havens")
+	HandleExitCoder(err)
+
+	expect(t, exitCode, 1)
+	expect(t, called, true)
+	expect(t, ErrWriter.(*bytes.Buffer).String(), "gourd havens\n")
+}
+
+func TestHandleExitCoder_ErrorWithoutMessage(t *testing.T) {
+	exitCode := 0
+	called := false
+
+	OsExiter = func(rc int) {
+		exitCode = rc
+		called = true
+	}
+	ErrWriter = &bytes.Buffer{}
+
+	defer func() {
+		OsExiter = fakeOsExiter
+		ErrWriter = fakeErrWriter
+	}()
+
+	err := errors.New("")
+	HandleExitCoder(err)
+
+	expect(t, exitCode, 0)
+	expect(t, called, false)
+	expect(t, ErrWriter.(*bytes.Buffer).String(), "")
+}