JEP 463: Implicitly Declared Classes (Second Preview) - Draft Spec Clarification

[leonid.arbouzov at oracle.com]

Hi Ron,

The JCK may not launch the source file directly because JEP 330 [1] has 
JDK scope and not Java SE scope
(i.e. Java implementations are not required to support the feature 
"Launch Single-File Source-Code Programs").

How the JCK can launch a test class not knowing its name in an 
implementation-independent manner?

Thanks,
Leonid
JCK Team

[1] https://openjdk.org/jeps/330

On 11/27/23 10:20 AM, Ron Pressler wrote:
>
>> On 27 Nov 2023, at 12:38, Sivakumar Gurusamy 
>> <sivakumar.gurusamy at oracle.com> wrote:
>>
>> Hello All,
>> The JEP 445 (Unnamed Classes and Instance Main Methods (First 
>> Preview)) didn't define class name generated for unnamed classes that 
>> made difficult to develop JCK21 tests.
>> Thanks to the change in JEP 463 (Implicitly Declared Classes and 
>> Instance Main Methods (Second Preview)). Now more JCK22 test can be 
>> developed and run.
>> But some difficulty remain: As per JEP 463 class name is "determined 
>> by the host system".
>> The spec hints typical algorithm how the class name can be generated.
>> But what JCK tests can do in other (non-typical) cases ?
>> A question: Can a host generate arbitrary class name 
>> indeterministically/randomly?
>> If the generated class name can't be determined then execution step 
>> has to be skipped thus weakening tests.
>> Please suggest.
>> Thank you,
>> JCK Team
> Hi.
>
> Let me first answer your question with a question: As the JEP and spec 
> change state, the host-selected class name cannot and must not be used 
> by Java source code; in that case, what tests specifically would you 
> like to write that an arbitrarily chosen name could complicate?
>
> Because the class name cannot be used in source code, there is nothing 
> you can do with the class other than launch it, i.e. invoke its 
> selected main method as the program’s entry point.
>
> The assumption is that the chosen class name is either irrelevant for 
> the launching process (when the source file is launched directly in 
> source code mode, where the launcher is given the name of the .java 
> file rather than the class name) or (possibly implicitly) made known 
> to the user by the compiler; i.e. when you compile Foo.java, javac 
> will produce a class file (typically Foo.class and perhaps others) 
> that will then be used when launching the program, either directly on 
> the command line or in the Main-Class attribute of an executable JAR’s 
> manifest.
>
> — Ron