data-decoder

A data decoding util based on mapstructure package The main target of this package is to solve the problem when requiring nested values from viper. Viper doesn't process environment values as structured value, this causes problem when unmarshalling value to structs. Decoder requires value for nested struct fields particularly if it's not found from the data map required for it's parent struct. Environment values are used if the value is not defined in map-typed data in config files.

Examples

Environments

LOGGING_FILE_PATH=decoder.log

viper vs data-decoder

Contents in yaml file

logging:
  level: debug

Logging Config Model

type LoggingConfigModel1 struct {
	Level string
	File  struct {
		Path string
	}
}

Using viper

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()

v.MergeInConfig()
cfgModel := LoggingConfigModel1{}
fmt.Println("logging.file.path:", v.Get("logging.file.path"))
v.UnmarshalKey("logging", &cfgModel)
fmt.Println("cfgModel:", cfgModel)

Result

logging.file.path: decoder.log
cfgModel: {debug {}}

Using data-decoder

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()
v.MergeInConfig()

d := decoder.NewDecoder(v)

cfgModel := LoggingConfigModel1{}
fmt.Println("logging.file.path:", v.Get("logging.file.path"))
d.Decode("logging", &cfgModel)
fmt.Println("cfgModel:", cfgModel)

Result

logging.file.path: decoder.log
cfgModel: {debug {decoder.log}}

Using query options

Disable nested query

Models

type LoggingConfigModel2 struct {
	Level string
	File  struct {
		Path string `query-option:"no"`
	}
}

type LoggingConfigModel3 struct {
	Level string
	File  struct {
		Path string
	} `query-option:"no"`
}

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()
v.MergeInConfig()

d := decoder.NewDecoder(v)

cfgModel2 := LoggingConfigModel2{}
fmt.Println(v.Get("logging.file.path"))
d.Decode("logging", &cfgModel2)
fmt.Println("cfgModel2:", cfgModel2)

cfgModel3 := LoggingConfigModel3{}
fmt.Println(v.Get("logging.file.path"))
d.Decode("logging", &cfgModel3)
fmt.Println("cfgModel3:", cfgModel3)

Result

decoder.log
cfgModel2: {debug {}}
decoder.log
cfgModel3: {debug {}}

Use bypass together with viper alias

Environment

LOGGING_CONFIG_FILE=decoder.log

Model

type LoggingConfigModel4 struct {
	Level string
	File  struct {
		Path string
	} `query-option:"bypass"`
}

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()
v.MergeInConfig()

v.RegisterAlias("logging.file.path", "logging.file")

d := decoder.NewDecoder(v)
cfgModel4 := LoggingConfigModel4{}
fmt.Println(v.Get("logging.file.path"))
d.Decode("logging", &cfgModel4)
fmt.Println("cfgModel4:", cfgModel4)

Result

decoder.log
cfgModel4: {debug {decoder.log}}