A Kong configuration loader for HCL

This is version 1.x of kong-hcl. Version 2 of this package uses the HCL2 library but is otherwise largely a drop-in replacement (see the README for details).

Use it like so:

var cli struct {
    Config kong.ConfigFlag `help:"Load configuration."`
}
parser, err := kong.New(&cli, kong.Configuration(konghcl.Loader, "/etc/myapp/config.hcl", "~/.myapp.hcl))

Mapping HCL fragments to a struct

More complex structures can be loaded directly into flag values by implementing the kong.MapperValue interface, and calling konghcl.DecodeValue.

The value can either be a HCL(/JSON) fragment, or a path to a HCL file that will be loaded. Both can be specified on the command-line or config file.

eg.

type NestedConfig struct {
	Size int
	Name string
}

type ComplexConfig struct {
	Key bool
	Nested map[string]NestedConfig
}

func (c *ComplexConfig) Decode(ctx *kong.DecodeContext) error {
	return konghcl.DecodeValue(ctx, c)
}

// ...

type Config struct {
	Complex ComplexConfig
}

Then the following .hcl config fragment will be decoded into Complex:

complex {
  key = true
  nested first {
    size = 10
    name = "first name"
  }
  nested second {
    size = 12
    name = "second name"
  }
}

Configuration layout

Configuration keys are mapped directly to flags.

Additionally, HCL block keys will be used as a hyphen-separated prefix when looking up flags.

Example

The following Kong CLI:

type CLI struct {
  Debug bool
  DB struct {
    DSN string
    Trace bool
  } `embed:"" prefix:"db-"`
}

Maps to the following flags:

--debug
--db-dsn=<string>
--db-trace

And can be configured via the following HCL configuration file...

debug = true

db {
    dsn = "root@/database"
    trace = true
}