Optional positional arguments that get skipped if corresponding validation fails

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Issue by ducaale
Tuesday Sep 01, 2020 at 18:51 GMT
Originally opened as clap-rs/clap#2122

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Describe your use case

I am trying re-implement HTTPie cli using clap-rs/structopt. I would like to have something like this

yahc.exe [METHOD] <URL> [REQUEST_ITEM]...

where METHOD is an optional positional arg enum with a default value

Describe the solution you'd like

It would be good if clap-rs allowed multiple optional positional arguments that get filled with a default value whenever the corresponding value fails to parse. For example, if we had:

test.exe [arg1] [arg2] [arg3]...

where:

• arg1 has a type of enum Arg1 { Foo, Bar } and defaults to Arg1::Bar
• arg2 has a type of u32 and defaults to 0
• arg3 has a type of Vec<String>

a user can use the CLI app in the following ways:

• test.exe: arg1 = default_value, arg2 = default_value, arg3 = default_value
• test.exe foo: arg1 = foo, arg2 = default_value, arg3 = default_value
• test.exe 1: arg1 = default_value, arg2 = 1, arg3 = default_value
• test.exe hello: arg1 = default_value, arg2 = default_value, arg3 = [hello]
• test.exe foo hello: arg1 = foo, arg2 = default_value, arg3 = [hello]

Alternatives, if applicable

I tried using the following but they didn't fit my use case:

• AllowMissingPositional can only be used when the last positional argument is required
• optional subcommands cannot be followed by positional args if the subcommand is omitted

Additional context

clap-rs/clap#2120

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Comment by pksunkara
Thursday May 20, 2021 at 18:28 GMT

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Might be related to #975