How to pass compiler options when running a single-file source-code Java program?

[Jonathan Gibbons]

On 12/18/18 1:04 AM, Gunnar Morling wrote:
> Thanks for the confirmation!
>
>> but maybe we could add a Note with the currently applicable options.
> Yes, that'd be helpful.
>
>> Even if we were to open up access to some additional javac options when using the source launcher, it is not likely that we would expose that particular option.
> I see. I feel this convolutes one prime use case of source file mode
> though, which is using it to explore new (including preview) language
> features. Given I'm explicitly opting into using the preview mode, it
> IMO adds unnecessary noise to the program output. E.g. see this little
> example where the node adds quite some verbosity to the output:
>
>      https://twitter.com/gunnarmorling/status/1074635092566384641
>
> In addition one cannot even do what the note says, as the
> -Xlint:preview option is unsupported in source file mode, too.
>
> So if there's no way to pass -XDsuppressNotes, could you perhaps
> consider to implicitly suppress that note when running in source file
> mode with preview enabled?

Suppressing the note entirely would require changes to JEP 12,
which specifies that javac generates a note when it detects the use
of preview features. That being said, it may be reasonable to
modify/remove the suggestion to use -Xlint in circumstances
like this when the option is not available.

-- Jon


>
> Thanks,
>
> --Gunnar
>
> Am Mo., 17. Dez. 2018 um 20:04 Uhr schrieb Jonathan Gibbons
> <jonathan.gibbons at oracle.com>:
>>
>> On 12/16/18 2:04 AM, Gunnar Morling wrote:
>>> Hi,
>>>
>>> I'd like to use JEP 330 [1] to run a single-file source-code program
>>> with Java (>= 11).
>>>
>>> Doing so, I'd like to pass options understood by javac but not by the
>>> runtime (java), e.g. -XDsuppressNotes. But this causes e.g. the
>>> following invocation to fail:
>>>
>>>       java --enable-preview --source=12 -XDsuppressNotes Test.java
>>>
>>>       Unrecognized option: -XDsuppressNotes
>>>       Error: Could not create the Java Virtual Machine.
>>>       Error: A fatal exception has occurred. Program will exit.
>>>
>>> There's this related sentence in the JEP:
>>>
>>>> The source-launcher implementation class has access to any relevant
>>>> command-line options, such as those to define the class path, module path,
>>>> and the module graph, and passes those options to the compiler to configure
>>>> the compilation environment.
>>> So I'd expect an option such as -XDsuppressNotes to be propagated, but
>>> it seems there's no authoritative list of options propagated to javac
>>> defined.
>> That's not the intent of the sentence in the JEP.
>>
>> The intent of the sentence is that if there are any runtime options
>> that could/should reasonably be applied in the context of the compilation
>> environment, then those options will be passed through to the
>> compiler.  There has never been any intent to provide a mechanism
>> to pass arbitrary options to the compiler when using the source-launcher
>> feature of the Java launcher.
>>
>> The set of applicable options was not specified explicitly, so as not
>> to preclude options being added in future -- but maybe we could
>> add a Note with the currently applicable options.  The list is
>>
>> --add-exports
>> --add-modules
>> --class-path -classpath -cp
>> --enable-preview
>> --limit-modules
>> --module-path -p
>> --patch-module
>> --upgrade-module-path
>>
>>
>>> Is there any way to pass this option when implicitly invoking the
>>> compiler through the java command in this case?
>> No.  If you want to specify arbitrary javac options, use javac.
>>
>> I would also note that you are trying to use a -XD option.
>> That is a non-standard, undocumented, unsupported option for javac.
>> Even if we were to open up access to some additional javac options
>> when using the source launcher, it is not likely that we would expose
>> that particular option.
>>
>> -- Jon
>>
>>> Thanks,
>>>
>>> --Gunnar
>>>
>>> [1] https://openjdk.java.net/jeps/330