overwrite with null value

config_examples/configuration/defaults/service.yaml

@@ -4,4 +4,5 @@ defaults:
     level: "warn"
     format: "json"
   host: "127.0.0.1"
-  port: "8888"
+  port: "8888"
+  string_value: string

config_examples/configuration/dev/service.yaml

@@ -1,2 +1,3 @@
 dev:
-  debug: true
+  debug: true
+  string_value: null

go.mod

@@ -3,7 +3,7 @@ module github.com/spacetab-io/configuration-go
 go 1.14
 
 require (
-	github.com/imdario/mergo v0.3.9
+	github.com/imdario/mergo v0.3.10-0.20200517151347-9080aaff8536
 	github.com/stretchr/testify v1.5.1
 	gopkg.in/yaml.v2 v2.3.0
 )

go.sum

@@ -1,7 +1,7 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/imdario/mergo v0.3.9 h1:UauaLniWCFHWd+Jp9oCEkTBj8VO/9DKg3PV3VCNMDIg=
-github.com/imdario/mergo v0.3.9/go.mod h1:2EnlNZ0deacrJVfApfmtdGgDfMuh/nq6Ok1EcJh5FfA=
+github.com/imdario/mergo v0.3.10-0.20200517151347-9080aaff8536 h1:X5Ang7dBiLOoIANjgXiArEGrPWSjFQdaUjtsV9+gC5I=
+github.com/imdario/mergo v0.3.10-0.20200517151347-9080aaff8536/go.mod h1:2EnlNZ0deacrJVfApfmtdGgDfMuh/nq6Ok1EcJh5FfA=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

reader.go

@@ -88,7 +88,7 @@ func ReadConfigs(cfgPath string) ([]byte, error) {
 			}
 
 			cc := configs[folder]
-			_ = mergo.Merge(&cc, configFromFile[folder], mergo.WithOverride)
+			_ = mergo.Merge(&cc, configFromFile[folder], mergo.WithOverwriteWithEmptyValue)
 
 			configs[folder] = cc
 
@@ -101,7 +101,7 @@ func ReadConfigs(cfgPath string) ([]byte, error) {
 	config := configs[defaultStage]
 
 	if c, ok := configs[stage]; ok {
-		if err := mergo.Merge(&config, c, mergo.WithOverride); err == nil {
+		if err := mergo.Merge(&config, c, mergo.WithOverwriteWithEmptyValue); err == nil {
 			iSay("Stage `%s` config is loaded and merged with `defaults`", stage)
 		}
 	}

reader_test.go

@@ -22,8 +22,9 @@ func TestReadConfigs(t *testing.T) {
 				Level  string `yaml:"level"`
 				Format string `yaml:"format"`
 			} `yaml:"log"`
-			Host string `yaml:"host"`
-			Port string `yaml:"port"`
+			Host        string `yaml:"host"`
+			Port        string `yaml:"port"`
+			StringValue string `yaml:"string_value"`
 		}
 
 		config := &cfg{}
@@ -38,8 +39,9 @@ func TestReadConfigs(t *testing.T) {
 				Level  string `yaml:"level"`
 				Format string `yaml:"format"`
 			}{Level: "error", Format: "text"},
-			Host: "127.0.0.1",
-			Port: "8888",
+			Host:        "127.0.0.1",
+			Port:        "8888",
+			StringValue: "",
 		}
 
 		assert.EqualValues(t, refConfig, config)