Programming @programming.dev matcha_addict @lemy.lol 1y ago

In CLI design, how to ask the user for a nested structured input?

Background

I am designing a CLI for a container build tool I am making. It uses Gentoo's Portage behind the scenes

Question

I want to give the user the ability to specify a custom package repository. The repository must have a name, URI and sync type.

custom_repo: {
    uri: 'https://...',
    name: 'custom',
    sync_type: 'git',
}

How do I have the user represent this in the CLI? keep in mind, this is not the main input and is optional.

One way is to make this only provide-able via a config file using JSON or another structured data representation. But I want to see if theres a good way to do it in the CLI

What I am thinking of: command --custom-repo uri='https://...',name=custom,sync_type=git --custom-repo ... [main input]

Is this the best way of doing this?

24 comments

Just pass in the name of a json file as a CLI input (or default the name and act on it if present or use it if indicated [e.g. /U == use json.config]).
- Yea, as a user I'd second the use of a configuration file - that approach tends to be much more convenient to use... especially since most users won't often change these values.
- I will definitely make that an option, but I would still want it to be invokable via CLI only if the user chooses. It makes scripting easier sometimes.
  
  How about a command-line flag to name an input file, but also process input as JSON, so someone can pipe it to your command or hand-write it if they're crazy?
- perhaps also useful in this case to document the shortcut of
  
  <(echo ‘{…}’)
  
  since not many people know about it, and it makes your tool work with things specified entirely on the command line rather than temp files
  
  alternatively —config-file and —config-json or similar
  
  making and cleaning up temp files when writing scripts is just such a massive PITA
If the json payload is small with finite keys you can support separate args for those keys. If you really need arbitrary json what you have described is fairly reasonable as a shorthand, similar to AWS CLI shorthand.

Honestly passing optional/advanced args as json via CLI isn't usually too bad since you can quote it with single quotes.
Can't this all be deduced from the URI?

https://github.com/org/project.git

The .git suffix indicates git, the project name is the stem (project).
- Nix does something like this with the protocol specifier: e.g. git+https://...
  
  I'm not sure what name means here exactly, but it might make sense to treat that separately, like git remotes:
  
  tool add [name] git+https://foo
- That is assuming it's hosted on github.
  
  That is an example URI.
For something like that i'd take a parameter like this (repeated as necessary):

--custom-repo=<name>=<synctype>+<url>

for example:

--custom-repo=custom=git+https://github.com/matcha/custom
What language? This would be simple with Python's argparse or Go's pflag.
I'm having the same problem. this kind of nested argument is quite annoying to program in e.g. argp. i am even thinking of using a minimal forth like parser to do this.
command --git-url https://... --alias myalias --svn-url http://... --alias mysvnalias

You may process it as a stack.

When reading within the program from stdin I recommend a state machine.
You could read json from standard input. Ex:

echo << EOF | command --read-stdin Some JSON EOF
Ask the user to customize a preset.json?
- That is certainly one solution and I plan to make that an option. But I'd still like to make the program invokable without having to write a file.
command --custom-repo-uri https://foo.com --custom-repo-name repo_name --custom-repo-sync-type git
- There could be multiple custom repos, so it would be difficult to know which uri goes with which repo name, and so on.

24 comments