From a0285163e1cf3c4d02a817aa1ed1d4cffc7e0a37 Mon Sep 17 00:00:00 2001
From: Dan Rollo <danrollo@gmail.com>
Date: Tue, 11 Aug 2020 19:26:27 -0400
Subject: [PATCH] ensure BindPFlag() detects a nil flag parameter before
 wrapping in pflagValue.

---
 viper.go      | 3 +++
 viper_test.go | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/viper.go b/viper.go
index c3130c2..8889f87 100644
--- a/viper.go
+++ b/viper.go
@@ -992,6 +992,9 @@ func (v *Viper) BindPFlags(flags *pflag.FlagSet) error {
 func BindPFlag(key string, flag *pflag.Flag) error { return v.BindPFlag(key, flag) }
 
 func (v *Viper) BindPFlag(key string, flag *pflag.Flag) error {
+	if flag == nil {
+		return fmt.Errorf("flag for %q is nil", key)
+	}
 	return v.BindFlagValue(key, pflagValue{flag})
 }
 
diff --git a/viper_test.go b/viper_test.go
index 09d5021..c38c665 100644
--- a/viper_test.go
+++ b/viper_test.go
@@ -970,6 +970,11 @@ func TestBindPFlag(t *testing.T) {
 	assert.Equal(t, "testing_mutate", Get("testvalue"))
 }
 
+func TestBindPFlagDetectNilFlag(t *testing.T) {
+	result := BindPFlag("testvalue", nil)
+	assert.Error(t, result)
+}
+
 func TestBindPFlagStringToString(t *testing.T) {
 	tests := []struct {
 		Expected map[string]string