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` (enriches everything including env vars)
`ParamEnricherDefault`	Explicit default: derives names, short flags, env vars, 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`)
`ParamEnricherEnv`	Generates `MY_PARAM` from flag name (UPPER_SNAKE_CASE)
`ParamEnricherBool`	Sets `default: false` for boolean params

Example - this struct:

type Params struct {
    ServerHost string
    MaxRetries int
    Verbose    bool
}

Automatically gets:

--server-host  (env: SERVER_HOST, required)
--max-retries  (env: MAX_RETRIES, required)
--verbose      (env: VERBOSE, default: false)

Custom Enrichers¶

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

Disable Auto Env Vars¶

Direct APIBuilder API

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

boa.NewCmdT[Params]("cmd").WithParamEnrich(
    boa.ParamEnricherCombine(
        boa.ParamEnricherName,
        boa.ParamEnricherShort,
        boa.ParamEnricherBool,
    ),
)

Prefix Env Vars¶

Direct APIBuilder API

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

boa.NewCmdT[Params]("cmd").WithParamEnrich(
    boa.ParamEnricherCombine(
        boa.ParamEnricherName,
        boa.ParamEnricherEnv,
        boa.ParamEnricherEnvPrefix("MYAPP"),
    ),
)

This turns MY_PARAM into MYAPP_MY_PARAM.

Disable Auto Short Flags¶

Direct APIBuilder API

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

boa.NewCmdT[Params]("cmd").WithParamEnrich(
    boa.ParamEnricherCombine(
        boa.ParamEnricherName,
        boa.ParamEnricherEnv,
        boa.ParamEnricherBool,
    ),
)

Disable All Enrichment¶

Direct APIBuilder API

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

boa.NewCmdT[Params]("cmd").WithParamEnrich(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 + Env + 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

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"`
}