Updated conformance text for Java SE 9 (JSR 379)

[mark.reinhold at oracle.com]

// Replying to both EG lists, for the record.

2017/7/25 11:15:57 -0700, volker.simonis at gmail.com:
> On Tue, Jul 11, 2017 at 7:10 PM,  <mark.reinhold at oracle.com> wrote:
>> Attached below is revised and expanded text for the "Conformance"
>> subsection of the "Modular platform" section [1] of the Java SE 9
>> (JSR 379) specification.  ...
>> 
>> ----
>> 
>> ...
>> 
>> As an aid to migration, an Implementation may relax the strong
>> encapsulation of the modules that it includes as follows:
>> 
>>  - An Implementation may provide a means to invoke its run-time system
>>    with one or more packages of one or more of its modules open to code
>>    in all unnamed modules, i.e., to code on the class path.  The first
>>    access to an element of such a package by a program via a reflection
>>    API must cause a warning to be issued on the standard error stream.
>>    Later accesses may also cause warnings to be issued.
>> 
>>  - An Implementation may, by default, open one or more packages of one
>>    or more of its modules to code in all unnamed modules.  If it does so
>>    then it must issue warnings as described in the previous paragraph.
>>    If it does so then it must, further, provide a means to invoke its
>>    run-time system without opening any packages of any of its modules.
>> 
>>    (The Reference Implementation's run-time system behaves this way by
>>     default, and because this is the default it can also be invoked
>>     without opening any of its packages via the command-line option
>>     `--illegal-access=deny`.)
> 
> This is still not totally clear to me. Does it mean the specification
> requires at least one warning for each package where we have an
> illegal access, for each module where we have an illegal access or is
> one single warning per invocation of the VM enough?

One single warning per invocation of the VM.  You're right -- this could
be more clear.  How about:

  - An Implementation may provide a means to invoke its run-time system
    with one or more packages of one or more of its modules open to code
    in all unnamed modules, i.e., to code on the class path.  If the
    run-time system is invoked in this way, and if by doing so some
    invocations of the reflection APIs succeed where otherwise they
    would have failed, then the first such invocation must cause a
    warning to be issued on the standard error stream.  Later such
    invocations may also cause warnings to be issued.

Is that better?

- Mark