From ec576f9765c4a5918918921e35a82f0907d77d36 Mon Sep 17 00:00:00 2001
From: Alex Flint <alex.flint@gmail.com>
Date: Thu, 9 Feb 2017 15:12:33 -0800
Subject: [PATCH] fix case where os.Args is empty

---
 parse.go      | 12 ++++++++++--
 parse_test.go | 14 ++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/parse.go b/parse.go
index 3cd00aa..a47f464 100644
--- a/parse.go
+++ b/parse.go
@@ -36,7 +36,7 @@ func MustParse(dest ...interface{}) *Parser {
 		fmt.Println(err)
 		os.Exit(-1)
 	}
-	err = p.Parse(os.Args[1:])
+	err = p.Parse(flags())
 	if err == ErrHelp {
 		p.WriteHelp(os.Stdout)
 		os.Exit(0)
@@ -57,7 +57,15 @@ func Parse(dest ...interface{}) error {
 	if err != nil {
 		return err
 	}
-	return p.Parse(os.Args[1:])
+	return p.Parse(flags())
+}
+
+// flags gets all command line arguments other than the first (program name)
+func flags() []string {
+	if len(os.Args) == 0 { // os.Args could be empty
+		return nil
+	}
+	return os.Args[1:]
 }
 
 // Config represents configuration options for an argument parser
diff --git a/parse_test.go b/parse_test.go
index dffebf4..8779b6f 100644
--- a/parse_test.go
+++ b/parse_test.go
@@ -654,3 +654,17 @@ func TestEmbedded(t *testing.T) {
 	assert.Equal(t, 321, args.Y)
 	assert.Equal(t, true, args.Z)
 }
+
+func TestEmptyArgs(t *testing.T) {
+	origArgs := os.Args
+
+	// test what happens if somehow os.Args is empty
+	os.Args = nil
+	var args struct {
+		Foo string
+	}
+	MustParse(&args)
+
+	// put the original arguments back
+	os.Args = origArgs
+}