Optique 0.8.0: Conditional parsing, pass-through options, and LogTape integration

[hongminhee@hackers.pub]

We're excited to announce Optique 0.8.0! This release introduces powerful new features for building sophisticated CLI applications: the conditional() combinator for discriminated union patterns, the passThrough() parser for wrapper tools, and the new @optique/logtape package for seamless logging configuration.

Optique is a type-safe combinatorial CLI parser for TypeScript, providing a functional approach to building command-line interfaces with composable parsers and full type inference.

New conditional parsing with conditional()

Ever needed to enable different sets of options based on a discriminator value? The new conditional() combinator makes this pattern first-class. It creates discriminated unions where certain options only become valid when a specific discriminator value is selected.

import { conditional, object } from "@optique/core/constructs";
import { option } from "@optique/core/primitives";
import { choice, string } from "@optique/core/valueparser";

const parser = conditional(
  option("--reporter", choice(["console", "junit", "html"])),
  {
    console: object({}),
    junit: object({ outputFile: option("--output-file", string()) }),
    html: object({ outputFile: option("--output-file", string()) }),
  }
);
// Result type: ["console", {}] | ["junit", { outputFile: string }] | ...

Key features:

• Explicit discriminator option determines which branch is selected
• Tuple result [discriminator, branchValue] for clear type narrowing
• Optional default branch for when discriminator is not provided
• Clear error messages indicating which options are required for each discriminator value

The conditional() parser provides a more structured alternative to or() for discriminated union patterns. Use it when you have an explicit discriminator option that determines which set of options is valid.

See the conditional() documentation for more details and examples.

Pass-through options with passThrough()

Building wrapper CLI tools that need to forward unrecognized options to an underlying tool? The new passThrough() parser enables legitimate wrapper/proxy patterns by capturing unknown options without validation errors.

import { object } from "@optique/core/constructs";
import { option, passThrough } from "@optique/core/primitives";

const parser = object({
  debug: option("--debug"),
  extra: passThrough(),
});

// mycli --debug --foo=bar --baz=qux
// → { debug: true, extra: ["--foo=bar", "--baz=qux"] }

Key features:

• Three capture formats: "equalsOnly" (default, safest), "nextToken" (captures --opt val pairs), and "greedy" (captures all remaining tokens)
• Lowest priority (−10) ensures explicit parsers always match first
• Respects -- options terminator in "equalsOnly" and "nextToken" modes
• Works seamlessly with object(), subcommands, and other combinators

This feature is designed for building Docker-like CLIs, build tool wrappers, or any tool that proxies commands to another process.

See the passThrough() documentation for usage patterns and best practices.

LogTape logging integration

The new @optique/logtape package provides seamless integration with LogTape, enabling you to configure logging through command-line arguments with various parsing strategies.

# Deno
deno add --jsr @optique/logtape @logtape/logtape

# npm
npm add @optique/logtape @logtape/logtape

Quick start with the loggingOptions() preset:

import { loggingOptions, createLoggingConfig } from "@optique/logtape";
import { object } from "@optique/core/constructs";
import { parse } from "@optique/core/parser";
import { configure } from "@logtape/logtape";

const parser = object({
  logging: loggingOptions({ level: "verbosity" }),
});

const args = ["-vv", "--log-output=-"];
const result = parse(parser, args);
if (result.success) {
  const config = await createLoggingConfig(result.value.logging);
  await configure(config);
}

The package offers multiple approaches to control log verbosity:

• verbosity() parser: The classic -v/-vv/-vvv pattern where each flag increases verbosity (no flags → "warning", -v → "info", -vv → "debug", -vvv → "trace")
• debug() parser: Simple --debug/-d flag that toggles between normal and debug levels
• logLevel() value parser: Explicit --log-level=debug option for direct level selection
• logOutput() parser: Log output destination with - for console or file path for file output

See the LogTape integration documentation for complete examples and configuration options.

Bug fix: negative integers now accepted

Fixed an issue where the integer() value parser rejected negative integers when using type: "number". The regex pattern has been updated from /^\d+$/ to /^-?\d+$/ to correctly handle values like -42. Note that type: "bigint" already accepted negative integers, so this change brings consistency between the two types.

Installation

# Deno
deno add jsr:@optique/core

# npm
npm add @optique/core

# pnpm
pnpm add @optique/core

# Yarn
yarn add @optique/core

# Bun
bun add @optique/core

For the LogTape integration:

# Deno
deno add --jsr @optique/logtape @logtape/logtape

# npm
npm add @optique/logtape @logtape/logtape

# pnpm
pnpm add @optique/logtape @logtape/logtape

# Yarn
yarn add @optique/logtape @logtape/logtape

# Bun
bun add @optique/logtape @logtape/logtape

Looking forward

Optique 0.8.0 continues our focus on making CLI development more expressive and type-safe. The conditional() combinator brings discriminated union patterns to the forefront, passThrough() enables new wrapper tool use cases, and the LogTape integration makes logging configuration a breeze.

As always, all new features maintain full backward compatibility—your existing parsers continue to work unchanged.

We're grateful to the community for feedback and suggestions. If you have ideas for future improvements or encounter any issues, please let us know through GitHub Issues. For more information about Optique and its features, visit the documentation or check out the full changelog.