From f1c29ce27310b85737d3e16771043bef9d11b25d Mon Sep 17 00:00:00 2001
From: Harrison Healey <harrisonmhealey@gmail.com>
Date: Wed, 20 Jun 2018 14:31:47 -0400
Subject: [PATCH] Allow environment variables to be set to empty string

---
 viper.go      | 14 +++++++-------
 viper_test.go | 15 +++++++++++++++
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/viper.go b/viper.go
index e9966ba..a338eb4 100644
--- a/viper.go
+++ b/viper.go
@@ -334,14 +334,14 @@ func (v *Viper) mergeWithEnvPrefix(in string) string {
 // rewriting keys many things, Ex: Get('someKey') -> some_key
 // (camel case to snake case for JSON keys perhaps)
 
-// getEnv is a wrapper around os.Getenv which replaces characters in the original
+// getEnv is a wrapper around os.LookupEnv which replaces characters in the original
 // key. This allows env vars which have different keys than the config object
 // keys.
-func (v *Viper) getEnv(key string) string {
+func (v *Viper) getEnv(key string) (string, bool) {
 	if v.envKeyReplacer != nil {
 		key = v.envKeyReplacer.Replace(key)
 	}
-	return os.Getenv(key)
+	return os.LookupEnv(key)
 }
 
 // ConfigFileUsed returns the file used to populate the config registry.
@@ -568,10 +568,10 @@ func (v *Viper) isPathShadowedInFlatMap(path []string, mi interface{}) string {
 //       "foo.bar.baz" in a lower-priority map
 func (v *Viper) isPathShadowedInAutoEnv(path []string) string {
 	var parentKey string
-	var val string
+	var ok bool
 	for i := 1; i < len(path); i++ {
 		parentKey = strings.Join(path[0:i], v.keyDelim)
-		if val = v.getEnv(v.mergeWithEnvPrefix(parentKey)); val != "" {
+		if _, ok = v.getEnv(v.mergeWithEnvPrefix(parentKey)); ok {
 			return parentKey
 		}
 	}
@@ -934,7 +934,7 @@ func (v *Viper) find(lcaseKey string) interface{} {
 	if v.automaticEnvApplied {
 		// even if it hasn't been registered, if automaticEnv is used,
 		// check any Get request
-		if val = v.getEnv(v.mergeWithEnvPrefix(lcaseKey)); val != "" {
+		if val, ok := v.getEnv(v.mergeWithEnvPrefix(lcaseKey)); ok {
 			return val
 		}
 		if nested && v.isPathShadowedInAutoEnv(path) != "" {
@@ -943,7 +943,7 @@ func (v *Viper) find(lcaseKey string) interface{} {
 	}
 	envkey, exists := v.env[lcaseKey]
 	if exists {
-		if val = v.getEnv(envkey); val != "" {
+		if val, ok := v.getEnv(envkey); ok {
 			return val
 		}
 	}
diff --git a/viper_test.go b/viper_test.go
index c93480e..fbf05f2 100644
--- a/viper_test.go
+++ b/viper_test.go
@@ -375,10 +375,17 @@ func TestEnv(t *testing.T) {
 	assert.Equal(t, "apple", Get("f"))
 	assert.Equal(t, "Cake", Get("name"))
 
+	os.Setenv("FOOD", "")
+
+	assert.Equal(t, "", Get("f"))
+
 	AutomaticEnv()
 
 	assert.Equal(t, "crunk", Get("name"))
 
+	os.Setenv("NAME", "")
+
+	assert.Equal(t, "", Get("name"))
 }
 
 func TestEnvPrefix(t *testing.T) {
@@ -396,9 +403,17 @@ func TestEnvPrefix(t *testing.T) {
 	assert.Equal(t, "apple", Get("f"))
 	assert.Equal(t, "Cake", Get("name"))
 
+	os.Setenv("FOO_ID", "")
+
+	assert.Equal(t, "", Get("id"))
+
 	AutomaticEnv()
 
 	assert.Equal(t, "crunk", Get("name"))
+
+	os.Setenv("FOO_NAME", "")
+
+	assert.Equal(t, "", Get("name"))
 }
 
 func TestAutoEnv(t *testing.T) {