Make mainBody behavior the default when parsing args

[holgerbrandl]

It took me quite a while (and frustration) to realize that my naive way of setting up a parser with

val args = ArgParser(args).parseInto(::MyArgs) 

wont give any help by default unless I wrap it with

val args = mainBody { ArgParser(args).parseInto(::MyArgs) }

Why can't parseInto catch the exception by default and print the help (similar to how mainBody works). Requiring a lambda here seems too much. A boolean parameter such as catchEx or similar (defaulting to to true) for parseInto seems more intuitive to me.

[xenomachina]

This does seem to be a common source of confusion, so it's definitely something I want to improve.

To answer your question, though, here's what I posted in an almost identical issue yesterday:

the reason the "mainBody" is separate from "parseInto" is to make testing easier. mainBody calls exitProcess and also writes directly to System.out/System.err, and none of that is very easy to test. So the idea is that mainBody has factored out a bunch of difficult to test bits. The body you pass to mainBody can do nothing but call a "testableMain" method, and your tests can test that same method.

Given that, I am somewhat reluctant to have the default behavior be "make my code hard to test".

[xenomachina]

Duplicate of #64

[holgerbrandl]

Thanks for detailing it out. Though, I personally would consider an easy and intuitive usage more important than testability.

Btw, what I did for https://github.com/holgerbrandl/kscript which suffers from a similar conceptual problem was to combine jvm-unit-testing with integration-level tests (error, exit codes) using assert.sh.