Nice write up. “Good” CLI semantics are pretty devilish, and overall I think clap does a pretty great job of picking the right (or at least most intuitive) behavior.
(One edge case that consistently trips me up, which other argument parsers similarly struggle with: an environment variable fallback has the same “weight” as its option counterpart, so any CLI that makes use of grouping/exclusivity will eventually hit user confusions where the user passes `--exclusive` and gets a failure because of an unrelated environment variable.)
The argument / environment variable duality is a challenging one, especially when developing server software that should take security into account where you don't want to encourage users to put secrets into scripts. Do you end up with some items that can only be entered via one mechanism or another? Maybe that's where the fun of being a developer comes in is making those choices.
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Nice write up. “Good” CLI semantics are pretty devilish, and overall I think clap does a pretty great job of picking the right (or at least most intuitive) behavior.
(One edge case that consistently trips me up, which other argument parsers similarly struggle with: an environment variable fallback has the same “weight” as its option counterpart, so any CLI that makes use of grouping/exclusivity will eventually hit user confusions where the user passes `--exclusive` and gets a failure because of an unrelated environment variable.)
The argument / environment variable duality is a challenging one, especially when developing server software that should take security into account where you don't want to encourage users to put secrets into scripts. Do you end up with some items that can only be entered via one mechanism or another? Maybe that's where the fun of being a developer comes in is making those choices.