From 3950cdc37c294ce06f873228ac96ad30b3876a2f Mon Sep 17 00:00:00 2001
From: Hugo Hromic <hhromic@gmail.com>
Date: Thu, 27 Jun 2024 00:02:41 +0100
Subject: [PATCH] Fix crash on errors in package-level `MustParse`

---
 parse.go      |  5 ++++-
 parse_test.go | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/parse.go b/parse.go
index 251b005..0d92df9 100644
--- a/parse.go
+++ b/parse.go
@@ -79,9 +79,12 @@ var ErrVersion = errors.New("version requested by user")
 // for monkey patching in example code
 var mustParseExit = os.Exit
 
+// for monkey patching in test code
+var mustParseOut io.Writer = os.Stdout
+
 // MustParse processes command line arguments and exits upon failure
 func MustParse(dest ...interface{}) *Parser {
-	return mustParse(Config{Exit: mustParseExit}, dest...)
+	return mustParse(Config{Exit: mustParseExit, Out: mustParseOut}, dest...)
 }
 
 // mustParse is a helper that facilitates testing
diff --git a/parse_test.go b/parse_test.go
index fe055fe..07af7ed 100644
--- a/parse_test.go
+++ b/parse_test.go
@@ -692,6 +692,21 @@ func TestMustParse(t *testing.T) {
 	assert.NotNil(t, parser)
 }
 
+func TestMustParseError(t *testing.T) {
+	var args struct {
+		Foo []string `default:""`
+	}
+	var exitCode int
+	var stdout bytes.Buffer
+	mustParseExit = func(code int) { exitCode = code }
+	mustParseOut = &stdout
+	os.Args = []string{"example"}
+	parser := MustParse(&args)
+	assert.Nil(t, parser)
+	assert.Equal(t, -1, exitCode)
+	assert.Contains(t, stdout.String(), "default values are not supported for slice or map fields")
+}
+
 func TestEnvironmentVariable(t *testing.T) {
 	var args struct {
 		Foo string `arg:"env"`