When to use goopt

goopt is particularly well-suited for:

  • Flexible command definition supporting struct-first, builder pattern, or imperative style
  • Multiple command organization approaches: support for a variety of command organization styles
  • Type-safe configurations with compile-time validation
  • Ordered command execution where commands need to be processed in sequence

Feature overview:

  • Flexible command organization:
    • Flag-centric with base paths
    • Command-centric with struct grouping
    • Hybrid approaches
  • Nested commands with command-specific flags
  • Command callbacks (explicit or automatic)
  • Environment variable support
  • Configurable defaults through ParseWithDefaults:
    • Load defaults from any source (JSON, YAML, etc.)
    • Implement only the configuration features you need
    • Clear precedence: Explicit ordering for configuration sources (Default values → ENV vars → config files → CLI flags) where CLI flags have the highest precedence
  • Ordered command execution
  • Type-safe flag parsing
  • Flag dependencies and validation
  • Pattern matching for flag values
  • Shell completion support:
    • Bash completion (flags and commands)
    • Zsh completion (rich command/flag descriptions, file type hints)
    • Fish completion (command/flag descriptions, custom suggestions)
    • PowerShell completion (parameter sets, dynamic completion)
    • Custom completion functions for dynamic values
    • Built-in completion installation commands

While Cobra and Viper provide a comprehensive configuration management solution with persistent and global flags, goopt offers unique flexibility in how commands and flags can be organized, along with guaranteed execution order.

Choose goopt when you:

  • Want freedom to choose between struct tags, builder pattern, or imperative style
  • Need flexibility in organizing commands (flag-centric, command-centric, or mixed)
  • Need guaranteed command execution order
  • Need strong compile-time guarantees about your command structure
  • Need completion support across multiple shell types
  • Prefer implementing specific configuration features over a full-featured solution

Guides

A number of guides are available to help you get started with goopt.

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