It would be useful for the jar tool to report the automatic module name that would be used if a regular jar file was put on the module path ( so there is an easy way for developers to determine the derived name ).
One way to achieve this is to repurpose the somewhat finger-some '--print-module-descriptor’ option, to report the automatic module name if the jar file does not contain a module-info.class. Given this, we should then probably give the option a better name, say ‘--describe-module’ ( similar to that of jmod's ‘describe’ subcommand ), e.g. $ touch resource $ jdk/bin/jar --create --file foo-6.jar resource $ jdk/bin/jar --describe-module --file foo-6.jar No module descriptor found. Derived automatic module: foo@6 It is also useful for the jar tool to indicate when a jar is not suitable to use as an automatic module, e.g. $ jdk/bin/jar --create --file ttt.jar T.class $ jdk/bin/jar --describe-module --file ttt.jar Unable to derive module descriptor for: ttt.jar T.class found in top-level directory (unnamed package not allowed in module) Webrev: http://cr.openjdk.java.net/~chegar/8176772.00/ https://bugs.openjdk.java.net/browse/JDK-8176772 Note: it is a deliberate decision to not print the synthesised module descriptor since the toString is not all that informative for an automatic module. The name is the most pertinent piece of information. -Chris.
