Required fields

A field with the required:"true" tag should have a value. Otherwise Parse returns tinyconf.ErrRequired.

type Config struct {
    DSN      string `env:"DSN" required:"true"`
    Password string `env:"PASSWORD" yaml:"password" hidden:"true" required:"true"`
    Port     int    `env:"PORT" initial:"8080"`
}

err := config.Parse(c)
if errors.Is(err, tinyconf.ErrRequired) {
    // field DSN: required value is not set; field Password: required value is not set
    log.Fatal(err)
}

What is a value

The field passes the check if any of these is true:

• some driver has set its value, even if the value is zero: PORT=0 is a value;
• the field has a non-zero value in the config that was passed to Parse.

So a required field without sources can still be filled in the code before Parse:

c := &Config{DSN: "postgres://localhost/dev"}
err := config.Parse(c) // DSN is not required to be in the environment

All at once

Parse checks all required fields and reports all missing ones in one error, together with the errors of drivers. The application can show the full list of what should be set in one start, not one variable per attempt.

Defaults and required

A field with a default value in the tag driver always has a value, so required makes sense only for the fields without defaults: secrets, addresses of external services.

Sub configs

When a sub config is parsed, only its own required fields are checked.