Question 1

How do I handle nested subcommands in Commander?

Accepted Answer

Define commands recursively using cmd.commands.add, as shown in the README with the 'kill <pid>' subcommand example. This allows creating hierarchical CLI structures with inherited flags and separate run blocks.

Question 2

Commander vs other CLI libraries for Crystal: which is better?

Accepted Answer

Commander excels with its DSL for complex, type-safe CLI tools, while libraries like OptionParser are lighter for basic parsing. Choose Commander for structured commands and automatic help; use simpler options if you only need minimal flag handling.

Question 3

How to add custom validation for flags in Commander?

Accepted Answer

Commander automatically validates types, but for custom logic, you can check options in the run block or pre-parse arguments. The README doesn't provide built-in custom validators, so you may need manual checks after parsing.

Question 4

Does Commander support auto-completion for bash or zsh?

Accepted Answer

No, Commander does not include built-in auto-completion generation for shells. You would need to implement it separately using Crystal code or external scripts, which is a limitation compared to some CLI libraries.

Question 5

How to test CLI applications built with Commander?

Accepted Answer

Test by mocking ARGV input and invoking Commander.run in unit tests. The README links to a file structure and testing answer, suggesting isolating command logic for easier testing without full CLI execution.

Question 6

Commander or hand-rolled parsing for simple Crystal tools?

Accepted Answer

For very simple tools with few flags, hand-rolled parsing using Crystal's ARGV might be faster. Commander is best when you need structured commands, type validation, or help pages to avoid boilerplate code.

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