Using default_missing_value without require_equals.

[lancelui-amzn]

Is there any way to specify a default missing value without requiring an equal sign in the argument? I have tried adding require_equals=false, and this seems to work in normal use cases. In what situations would it fail?

The desired usage is shown:
binary --option # valid with default value
binary --option value # valid with specified value

[epage]

In this situation, there are three properties at play

• default_missing_value
• require_equals
• num_args

require_equals is a recommendation related to num_args, not default_missing_value. See https://docs.rs/clap/latest/clap/struct.Arg.html#method.num_args

For example, in cargo we made the choice that subcommands that use num_args(0..=1) cannot have positional arguments.