8194937: Inconsistent behavior of --validate-modules when combined with -m and other options

[mandy chung]

The change looks good.  I'm glad that we get rid of the need for the 
minimal boot layer for validation and gets the option handling  consistent.

thanks
Mandy

On 6/20/18 11:40 PM, Alan Bateman wrote:
> 
> The java `--validatate-modules` option is a very useful option to scan 
> all modules to identify a wide range of issues such as conflicts, 
> duplicate modules in a directory, modules shadowed by modules of the 
> same name, malformed module descriptors and more.
> 
> We originally implemented this option as "launcher helper" where it runs 
> after the VM is started. This creates a chicken 'n egg scenario where 
> starting the VM might fail due to issues that the validation should 
> catch. To avoid that, the VM starts up with a minimal boot layer, just 
> java.base, which is enough to allow the launcher helpers to run before 
> the launcher exits. This works okay but it the effect of ignoring 
> options such as --add-modules and -m that would normally specify the 
> module roots. This just means that f you specify any of these options 
> with --validate-module then the module path will be validated as 
> expected but bad values specified to these other options are ignored.
> 
> To get the option handling consistent, I'd like to move the validation 
> from being a launcher helper so that it runs as part of the module 
> system initialization (only when --validate-module is specified of 
> course).  This allows the option to be combined with other options that 
> specify module name. It also allows the option to be used with other 
> "exiting options" such as -version, --list-modules and --describe-module.
> 
> The webrev with the changes is here. Note that the validation has not 
> changed, this is mostly a house move with some expansion of the tests to 
> cover combinations of options that we didn't test in the original 
> implementation.
>      http://cr.openjdk.java.net/~alanb/8194937/webrev/
> 
> -Alan