validation

README

Validation Example

This example demonstrates comprehensive validation features in goconfig, including:

• Min/Max validation for integers, floats, and durations
• Pattern validation for strings using regular expressions
• Custom validators for complex business logic
• Nested struct validation using dot notation

Running the Example

With Valid Configuration

export API_KEY="sk-1234567890abcdefghij"
export SERVER_PORT="8080"
export DB_USER="appuser"
go run .

Testing Validation Errors

Port out of range (below minimum)

export SERVER_PORT="80"  # Error: below minimum 1024
export API_KEY="sk-1234567890abcdefghij"
go run .

Port out of range (above maximum)

export SERVER_PORT="70000"  # Error: above maximum 65535
export API_KEY="sk-1234567890abcdefghij"
go run .

Invalid duration (below minimum)

export READ_TIMEOUT="100ms"  # Error: below minimum 1s
export API_KEY="sk-1234567890abcdefghij"
go run .

Invalid pattern (username with special characters)

export DB_USER="user@host"  # Error: doesn't match pattern ^[a-zA-Z0-9_]+$
export API_KEY="sk-1234567890abcdefghij"
go run .

Custom validation (API key too short)

export API_KEY="sk-short"  # Error: must be at least 20 characters
go run .

Custom validation (API key wrong prefix)

export API_KEY="pk-1234567890abcdefghij"  # Error: must start with 'sk-'
go run .

Features Demonstrated

Integer Range Validation

Port int `key:"SERVER_PORT" default:"8080" min:"1024" max:"65535"`

Float Range Validation

LoadFactor float64 `key:"LOAD_FACTOR" default:"0.75" min:"0.0" max:"1.0"`

Duration Range Validation

ReadTimeout time.Duration `key:"READ_TIMEOUT" default:"30s" min:"1s" max:"5m"`

String Pattern Validation

Hostname string `key:"HOSTNAME" default:"localhost" pattern:"^[a-zA-Z0-9.-]+$"`

Custom Validators

goconfig.WithValidator("API.APIKey", func(value any) error {
    key := value.(string)
    if !strings.HasPrefix(key, "sk-") {
        return fmt.Errorf("API key must start with 'sk-'")
    }
    return nil
})

Nested Field Validation

// Validates the Host field within the Database struct
goconfig.WithValidator("Database.Host", func(value any) error {
    // validation logic
    return nil
})

Validation Order

Validations are applied in this order:

1. Tag-based validation (min, max, pattern)
2. Custom validators (in the order they are registered)

All validations must pass for the configuration to be considered valid.