From bd4ecaf77cd70887a7dc2a937dd1304720833c18 Mon Sep 17 00:00:00 2001
From: psihachina <psihachina@gmail.com>
Date: Wed, 5 Oct 2022 14:37:47 +0300
Subject: [PATCH] added allowEmptyMap option

---
 viper.go      | 23 ++++++++++++++++++++++-
 viper_test.go | 12 ++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/viper.go b/viper.go
index 5f76cc0..a752f0c 100644
--- a/viper.go
+++ b/viper.go
@@ -205,6 +205,7 @@ type Viper struct {
 	automaticEnvApplied bool
 	envKeyReplacer      StringReplacer
 	allowEmptyEnv       bool
+	allowEmptyMap       bool
 
 	config         map[string]interface{}
 	override       map[string]interface{}
@@ -535,6 +536,15 @@ func (v *Viper) AllowEmptyEnv(allowEmptyEnv bool) {
 	v.allowEmptyEnv = allowEmptyEnv
 }
 
+// AllowEmptyMap tells Viper to consider set,
+// but empty maps as valid values instead of falling back.
+// For backward compatibility reasons this is false by default.
+func AllowEmptyMap(allowEmptyMap bool) { v.AllowEmptyMap(allowEmptyMap) }
+
+func (v *Viper) AllowEmptyMap(allowEmptyMap bool) {
+	v.allowEmptyMap = allowEmptyMap
+}
+
 // TODO: should getEnv logic be moved into find(). Can generalize the use of
 // rewriting keys many things, Ex: Get('someKey') -> some_key
 // (camel case to snake case for JSON keys perhaps)
@@ -1550,6 +1560,8 @@ func (v *Viper) ReadInConfig() error {
 		return err
 	}
 
+	fmt.Println(config)
+
 	v.config = config
 	return nil
 }
@@ -1582,7 +1594,9 @@ func ReadConfig(in io.Reader) error { return v.ReadConfig(in) }
 
 func (v *Viper) ReadConfig(in io.Reader) error {
 	v.config = make(map[string]interface{})
-	return v.unmarshalReader(in, v.config)
+	err := v.unmarshalReader(in, v.config)
+	fmt.Println(v.config)
+	return err
 }
 
 // MergeConfig merges a new configuration with an existing config.
@@ -2011,6 +2025,13 @@ func (v *Viper) flattenAndMergeMap(shadow map[string]bool, m map[string]interfac
 			shadow[strings.ToLower(fullKey)] = true
 			continue
 		}
+
+		if v.allowEmptyMap {
+			if len(val.(map[string]interface{})) == 0 {
+				shadow[strings.ToLower(fullKey)] = true
+				continue
+			}
+		}
 		// recursively merge to shadow map
 		shadow = v.flattenAndMergeMap(shadow, m2, fullKey)
 	}
diff --git a/viper_test.go b/viper_test.go
index 926ffc2..1a114d6 100644
--- a/viper_test.go
+++ b/viper_test.go
@@ -60,6 +60,8 @@ type testUnmarshalExtra struct {
 var tomlExample = []byte(`
 title = "TOML Example"
 
+[ecs.test]
+
 [owner]
 organization = "MongoDB"
 Bio = "MongoDB Chief Developer Advocate & Hacker at Large"
@@ -669,6 +671,16 @@ func TestEmptyEnv_Allowed(t *testing.T) {
 	assert.Equal(t, "Cake", Get("name"))
 }
 
+func TestEmptyMap_Allowed(t *testing.T) {
+	initTOML()
+	AllowEmptyMap(true)
+
+	allkeys := sort.StringSlice(AllKeys())
+	allkeys.Sort()
+
+	assert.Equal(t, sort.StringSlice(sort.StringSlice{"ecs.test", "owner.bio", "owner.dob", "owner.organization", "title"}), allkeys)
+}
+
 func TestEnvPrefix(t *testing.T) {
 	initJSON()