[commons-cli] Adding prompting for omitted arguments

[David Barts <n5...@mac.com.INVALID>]

I’m going to be writing some command-line utilities which should prompt
for various parameters if they are not specified via an option and a
value on the command line. To that end, I am interested in adding a
feature to do this automatically in commons-cli.

I am also planning to add a way to specify how to interpret values for
an option as a type other than String (I know: PatternOptionBuilder can
do this, but only for single-letter options).

I was thinking of just writing my own personal code (based on
commons-cli) to do this, but figured I’d check to see if the dev team
thought it might make a good contribution to the code. (Might as well
share my efforts if others think they will be useful.)

Before  continuing, I will note none of the changes I propose would
alter the default behavior of commons-cli; existing code that does not
invoke the new features would continue to act the same. I am thinking of
doing something along the lines of the following:

*org.apache.commons.cli.Option* — Allow for two more parameters to be
specified: an interpolator and a prompt string. The former would be an
interface with a single abstract method whose purpose would be to
sanity-check (and, if needed, transform the option argument from a
string to another data type). The prompt string, if specified, will
cause the option’s associated value to be prompted for if the option was
not present on the command line. Both imply that the option in question
has an associated value.

*org.apache.commons.cli.DefaultParser* — This will have to honor the
interpolator and prompt features of the Option object.

*org.apache.commons.cli.CommandLine* — The getParsedOptionValue method
will return whatever the interpolator (if specified) parsed the option’s
value into.
*
**org.apache.commons.cli.InvalidArgumentException* — (new class,
subclass of ParseException) Can be thrown by an interpolator to indicate
that the option value in question was not valid.

Anyhow, I’d appreciate having some idea of whether the commons-cli dev
team would be welcome to a submission of such features on my part. It
won’t hurt my feelings any if the answer is “no.”

-- 
David Barts / n5jrn@me.com
He who has nothing to die for has nothing to live for.
 -- Moroccan proverb