use template literal types to call 'opts' with type safely

[anatawa12]

Since typescript 4.1, template literal types was coming.
This feature enables us to call the 'opts' function with type safety without specifying types, I think. Could you implement this?

[shadowspawn]

There is an experiment with this in #1356.

Related: #1245

[shadowspawn]

I think this may be too complex to do with the existing API. Deducing type for .opts() is hard enough, but there are also the arguments passed into the action handler. They are affected by .argument() as well!

An alternative interface for configuration might allow type deduction and a different style of setup (e.g. #665), in situations where preference or the benefits make it attractive.

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I saw an interesting related statement in the Clipanion documentation:

We won't provide domain-specific languages (DSL). Once upon a time Clipanion actually worked like this, using a "natural" language to declare commands, but over time it became clear that we were merely fighting JavaScript, losing many useful tooling integrations.

https://mael.dev/clipanion/docs/

[shadowspawn]

This issue has not had any activity in a month. It isn't likely to get acted on due to this report.

Feel free to open a new issue if it comes up again, with new information and renewed interest.

Thank you for your contributions.

[shadowspawn]

For some experimental strong inferred typing see: https://github.com/commander-js/extra-typings