Cleye

const argv = cli({
    parameters: ['<required>', '[optional]', '[rest...]']
})
argv._.required // string
argv._.optional // string | undefined
argv._.rest // string[]
argv._['--'] // string[] — everything after --

Multi-word names use camelCase on argv._: '<first name>' → argv._.firstName.

Flags

const argv = cli({
    flags: {
        verbose: Boolean, // shorthand
        output: {
            type: String,
            alias: 'o',
            default: 'dist',
            description: 'Output directory',
            placeholder: '<path>'
        },
        count: {
            type: [Number], // array: -n 1 -n 2
            alias: 'n'
        }
    }
})

argv.flags.verbose // boolean | undefined
argv.flags.output // string
argv.flags.count // number[]

Flag name is camelCase; parsed from kebab-case CLI input (--output-dir → outputDir).

Delimiters — =, :, and . all work as value separators:

--flag=value   --flag:value   --flag.value

Use : when the value itself contains = (e.g. --define:KEY=VALUE).

Counting flags — use [Boolean] and check .length:

cli({
    flags: {
        verbose: {
            type: [Boolean],
            alias: 'v'
        }
    }
})
// -vvv → argv.flags.verbose.length === 3

Optional value — custom type returns true when no value is given:

const OptionalString = (value: string) => value || true
cli({ flags: { tag: OptionalString } })
// --tag        → true
// --tag beta   → 'beta'

Boolean Flag Negation

By default, set a boolean flag to false using the = operator:

--verbose=false   # → false
--verbose false   # → true (false treated as separate argument)

To also support the --no-<flag> convention, enable booleanFlagNegation (additive — =false still works):

cli({
    flags: { verbose: Boolean },
    booleanFlagNegation: true
})
// --no-verbose     → false
// --verbose=false  → false (still works)
// Last-wins: --verbose --no-verbose → false

Commands inherit booleanFlagNegation from the parent cli() but can override it.

Strict Flags

cli({
    flags: { foo: Boolean },
    strictFlags: true
})
// --baz → Error: Unknown flag: --baz. (Did you mean --foo?)

Commands inherit strictFlags but can override it.

Commands

// install-command.ts
export const installCommand = command({
    name: 'install',
    alias: ['i', 'add'],
    parameters: ['<package name>'],
    flags: { saveDev: Boolean }
}, (argv) => {
    argv._.packageName // string
    argv.flags.saveDev // boolean | undefined
})

// main.ts
cli({
    name: 'npm',
    version: '1.0.0',
    commands: [installCommand]
})

When a command is matched, argv.command narrows the type for type-safe branching.

Help & Version

cli({
    name: 'my-script',
    version: '1.2.3', // enables --version; also shown in --help
    help: {
        description: 'Does things',
        usage: 'my-script [flags] <file>',
        examples: ['my-script foo.txt', 'my-script --output=dist foo.txt'],
        version: '1.2.3' // show version in --help without handling --version
    }
})
// help: false  — disables --help handling; call argv.showHelp() manually

Tip: import name, version, and description from package.json to avoid keeping them in sync manually:

import { name, version, description } from './package.json' with { type: 'json' }

cli({
    name,
    version,
    help: { description }
})

Custom Flag Types

Any function (value: string) => T works as a flag type — the return type is inferred.

// Validation + narrowing
const Port = (value: string) => {
    const n = Number(value)
    if (!Number.isInteger(n) || n < 1 || n > 65_535) { throw new Error(`Invalid port: ${value}`) }
    return n
}
// argv.flags.port → number

// Enum
const sizes = ['small', 'medium', 'large'] as const
const Size = (v: string) => {
    if (!(sizes as readonly string[]).includes(v)) { throw new Error(`Expected: ${sizes.join(', ')}`) }
    return v as typeof sizes[number]
}
// argv.flags.size → 'small' | 'medium' | 'large'

// Comma-separated list
const List = (v: string) => v.split(',')
// --tags a,b,c → argv.flags.tags === ['a', 'b', 'c']

// Inline JSON
cli({ flags: { data: JSON.parse } })
// --data '{"key":1}' → argv.flags.data === { key: 1 }

// Dot-nested object (combine with . delimiter)
const Env = (v: string): Record<string, string | true> => {
    const [k, value] = v.split('=')
    return { [k]: value ?? true }
}
cli({ flags: { env: [Env] } })
// --env.TOKEN=abc --env.CI → merge to { TOKEN: 'abc', CI: true }

Type Helpers (cleye/formats)

cleye/formats ships composable, tree-shakable type-function helpers. Import only what you need.

import {
    oneOf, commaList, integer, float, range, url
} from 'cleye/formats'

• oneOf('a', 'b', 'c') — infers 'a' | 'b' | 'c'; throws if the value is not in the list.
• commaList(itemType) — splits "a,b,c" → T[]; trims whitespace; composes with other helpers (e.g. commaList(integer())).
• integer() — base-10 integer; throws on floats/non-numeric.
• float() — finite float; throws on Infinity/non-numeric.
• range(min, max) — returns (input: string) => number; validates input parses to a number in [min, max].
• url() — parses with new URL(); returns a URL object (not a string).

Help Customization

cli({
    help: {
        render(nodes, renderers) {
            nodes.push('\nDocs: https://example.com')
            renderers.flagOperator = () => '=' // --flag=<value>
            return renderers.render(nodes)
        }
    }
})

Default renderers: /src/render-help/renderers.ts.

ignoreArgv

cli({
    ignoreArgv(type, flagOrArgv, value) {
        if (type === 'unknown-flag') { return true } // silently skip unknown flags
    }
})

type: 'known-flag' | 'unknown-flag' | 'argument'

Return Type

type ParsedArgv = {
    _: string[] & Parameters
    flags: { [name: string]: InferredType }
    unknownFlags: { [name: string]: (string | boolean)[] }
    showVersion: () => void
    showHelp: (options?: HelpOptions) => void
}

TypeScript Exports

import type { Flags, Renderers, TypeFlag } from 'cleye'