RFR: 7903741: some test properties are not documented

[Jonathan Gibbons]

On Fri, 7 Jun 2024 01:01:14 GMT, Iris Clark <iris at openjdk.org> wrote:

>> Please review a simple doc and test update for tag-spec.html, after it was recently noted that `test.module.path` was available but not documented.
>> 
>> The new test verifies 1:1 correspondence between names that are available, as env vars or system properties, and those that are documented.
>
> test/tag-spec/TestTagSpec.gmk line 45:
> 
>> 43: 		$(JAVAFILES.com.sun.javatest.regtest-tools)
>> 44: 	$(GREP) -oh '\(.put(\|put(map, \)"test.[^"]*' $(JAVAFILES.com.sun.javatest.regtest-tools) | \
>> 45: 		$(GREP) -v "test.class.path.prefix" | \
> 
> Why do we want to ignore this sysprop?  It's not defined in the tag spec, but why is it defined... convenience?

`test.class.path.prefix` is part of the internal mechanism for the `@run main` and `@compile` actions in "agent mode". It is prepended to the system property `java.class.path` for the duration of the test.

It's not clear to me how useful this is. It is now well-defined that ... _The system property "java.class.path" is read during early initialization of the VM to determine the class path._ So changing the system property later is not of much benefit, except maybe to tests that want to propagate the value into child VMs.

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PR Review Comment: https://git.openjdk.org/jtreg/pull/203#discussion_r1631541998