Auto-Derivation & Enrichers¶

BOA automatically derives flag names, environment variables, and other metadata from your struct fields. This is done through enrichers - functions that process parameters during initialization.

ParamEnrich Field¶

The ParamEnrich field controls which enricher is used:

Value	Behavior
`nil`	Uses `ParamEnricherDefault` (derives names, short flags, and bool defaults)
`ParamEnricherDefault`	Explicit default: derives names, short flags, and bool defaults
`ParamEnricherNone`	No enrichment - you must specify everything via struct tags

Default Behavior¶

By default (when ParamEnrich is nil), BOA applies ParamEnricherDefault, which includes:

Enricher	What it does
`ParamEnricherName`	Converts `MyParam` -> `--my-param` (kebab-case)
`ParamEnricherShort`	Auto-assigns `-m` from first char (skips conflicts, reserves `-h`)
`ParamEnricherBool`	Sets `default: false` for boolean params

Note: Environment variable binding is not included by default. Add ParamEnricherEnv explicitly if you want auto-generated env vars.

Example - this struct:

type Params struct {
    ServerHost string
    MaxRetries int
    Verbose    bool
}

Automatically gets:

--server-host  (required)
--max-retries  (required)
--verbose      (default: false)

Custom Enrichers¶

You can compose your own enricher to change the default behavior.

Enable Auto Env Vars¶

boa.CmdT[Params]{
    Use: "cmd",
    ParamEnrich: boa.ParamEnricherCombine(
        boa.ParamEnricherName,
        boa.ParamEnricherShort,
        boa.ParamEnricherEnv,
        boa.ParamEnricherBool,
    ),
}

Prefix Env Vars¶

boa.CmdT[Params]{
    Use: "cmd",
    ParamEnrich: boa.ParamEnricherCombine(
        boa.ParamEnricherName,
        boa.ParamEnricherEnv,
        boa.ParamEnricherEnvPrefix("MYAPP"),
    ),
}

This turns MY_PARAM into MYAPP_MY_PARAM.

Disable Auto Short Flags¶

boa.CmdT[Params]{
    Use: "cmd",
    ParamEnrich: boa.ParamEnricherCombine(
        boa.ParamEnricherName,
        boa.ParamEnricherEnv,
        boa.ParamEnricherBool,
    ),
}

Disable All Enrichment¶

boa.CmdT[Params]{
    Use:         "cmd",
    ParamEnrich: boa.ParamEnricherNone,
}

With no enrichment, you must specify everything via struct tags:

type Params struct {
    Host string `name:"host" short:"h" env:"HOST" descr:"Server host"`
}

Available Enrichers¶

Enricher	Description
`ParamEnricherDefault`	Combines Name + Short + Bool
`ParamEnricherName`	Derives flag name from field name
`ParamEnricherShort`	Auto-assigns short flags
`ParamEnricherEnv`	Derives env var from flag name
`ParamEnricherEnvPrefix(prefix)`	Adds prefix to env vars
`ParamEnricherBool`	Sets false default for booleans
`ParamEnricherCombine(...)`	Combines multiple enrichers

Interaction with Named Struct Prefixing¶

When a field lives inside a named (non-anonymous) struct field, enrichers operate on the already-prefixed name. For example:

type DBConfig struct {
    Host string `default:"localhost"`
    Port int    `default:"5432"`
}

type Params struct {
    DB DBConfig  // named field
}

With ParamEnricherDefault, DB.Host gets:

Prefix applied: field name becomes DBHost internally
ParamEnricherName: converts DBHost → --db-host
ParamEnricherShort: assigns -d (if available)

With ParamEnricherEnv added, the flag name db-host is converted to env var DB_HOST.

Explicit env:"..." tags inside named struct fields are also prefixed: env:"SERVER_HOST" inside field API becomes API_SERVER_HOST.

Override Auto-Derived Values¶

Struct tags always take precedence over enrichers:

type Params struct {
    // Enricher would derive --my-host and MY_HOST
    // Tags override to --server and APP_SERVER
    MyHost string `name:"server" env:"APP_SERVER"`
}

Note: Inside named struct fields, explicit name and env tags are also prefixed. name:"host" inside field DB becomes --db-host.