Options & Arguments

CLI commands usually accept more than just positional arguments. Moost provides decorators for flags (--verbose), short aliases (-v), optional parameters, and typed values.

Positional arguments

Positional arguments come from :param segments in the command path. Extract them with @Param():

@Cli('deploy/:env')
deploy(@Param('env') env: string) {
  return `Deploying to ${env}`
}

my-cli deploy production     # → Deploying to production

Add @Description() to document what the argument means (shown in --help):

@Cli('deploy/:env')
deploy(
  @Description('Target environment (production, staging, dev)')
  @Param('env')
  env: string,
) {
  return `Deploying to ${env}`
}

Option flags

Use @CliOption() to bind a parameter to a CLI flag. Pass one or more keys — long names become --flag, single-character names become -f:

import { Cli, CliOption, Controller, Description, Param } from '@moostjs/event-cli'

@Controller()
export class DeployController {
  @Cli('deploy/:env')
  deploy(
    @Param('env') env: string,

    @Description('Project name')
    @CliOption('project', 'p')
    project: string,

    @Description('Enable verbose logging')
    @CliOption('verbose', 'v')
    verbose: boolean,
  ) {
    if (verbose) console.log(`Project: ${project}, env: ${env}`)
    return `Deploying ${project} to ${env}`
  }
}

my-cli deploy production --project my-app --verbose
my-cli deploy production -p my-app -v          # same thing

Boolean flags

When a parameter has type boolean, Moost automatically registers it as a boolean flag. This means the flag doesn't expect a value — its presence means true:

@Cli('build')
build(
  @CliOption('watch', 'w')
  watch: boolean,

  @CliOption('minify', 'm')
  minify: boolean,
) {
  return `watch=${watch}, minify=${minify}`
}

my-cli build --watch --minify    # → watch=true, minify=true
my-cli build -wm                 # → same (combined short flags)
my-cli build                     # → watch=false, minify=false

Optional parameters

Mark a parameter as optional with @Optional(). Without it, a missing argument may result in undefined:

import { Cli, CliOption, Controller, Description, Optional } from '@moostjs/event-cli'

@Controller()
export class BuildController {
  @Cli('build')
  build(
    @Description('Output directory')
    @CliOption('out', 'o')
    @Optional()
    outDir: string,
  ) {
    return `Output: ${outDir ?? './dist'}`
  }
}

@Optional() records metadata only — it signals intent to readers of your code but does not change CLI parsing or help output. It does not set a default either; use ?? for fallback values.

Sample values

Use @Value() to show a placeholder in help output. This doesn't set a default — it only affects --help display:

import { Cli, CliOption, Controller, Description, Param } from '@moostjs/event-cli'
import { Value } from 'moost'

@Controller()
export class TestController {
  @Cli('test/:config')
  test(
    @Description('Configuration file')
    @Param('config')
    config: string,

    @Description('Target environment')
    @CliOption('target', 't')
    @Value('<staging>')
    target: string,

    @Description('Project name')
    @CliOption('project', 'p')
    @Value('<my-app>')
    project: string,
  ) {
    return `Testing ${config}: ${project} in ${target}`
  }
}

In --help, the options section shows --target=<staging> and --project=<my-app>.

Decorator summary

Decorator	Applies to	Purpose
@Param('name')	parameter	Extract positional argument from :name in path
@CliOption('key', 'k')	parameter	Bind to --key / -k flag
@Description('...')	parameter, method	Document for help output
@Optional()	parameter	Mark as not required
@Value('...')	parameter	Show sample value in help

Gotchas

1. Boolean detection needs the literal boolean type. A flag is parsed as boolean only when the parameter is typed exactly boolean (the type is read via emitDecoratorMetadata). Union types like boolean | undefined or string | boolean are not detected.
2. One option key, one type — app-wide. Option types are aggregated across all commands. A key is parsed as boolean only if every command using it types it boolean. Declaring --verbose as boolean in one command and string in another silently changes parsing for both.
3. Boolean flags are presence-only. --watch sets true; there is no --watch=false. A missing boolean flag resolves to false.
4. Non-boolean options consume the next token. my-cli build --out dist assigns 'dist' to --out. If you forget the value, the next positional argument is swallowed as the option value instead of reaching your @Param().

What's next

• Controllers — group related commands under prefixes
• Help System — customize auto-generated help output