RFR: 8345259: Disallow ALL-MODULE-PATH without explicit --module-path [v11]

[Mandy Chung]

On Tue, 17 Dec 2024 11:45:56 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Please review this extension to #22609 which now disallows `ALL-MODULE-PATH` without explicit `--module-path` option or a non-existent module path. In addition, this fixes a bug mentioned in #22609 when `ALL-MODULE-PATH` and `--limit-modules` are used in combination. It failed earlier and passes now due to alignment of `ModuleFinder`s. With this patch JEP 493 enabled builds and regular JDK builds behave the same in terms of `ALL-MODULE-PATH`.
>> 
>> When an explicit module path is being added, there is no difference. All modules on that path will be added as roots. Tests have been added for the various cases and existing tests updated to allow for them to run on JEP 493 enabled builds. Thoughts?
>> 
>> Testing:
>> - [x] GHA, `test/jdk/tools/jlink` (all pass)
>> - [x] Added jlink test.
>
> Severin Gehwolf has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix comments

See below as my response to your question but I take back this proposal.  I'm ok to proceed as is and revisit this issue in the future.

> So this means `--limit-modules` has no meaning when `ALL-MODULE-PATH` is specified. It will be ignored.

I can't tell how it will be ignored.  Maybe missing something.

The transitive dependences of the modules specified to `--limit-modules` plus the modules specified to `--add-modules` are observable.   See the implementation of `limitFinder` method which do not compute the dependences of the modules specified to `--add-modules`.

>     * `jlink --add-modules ALL-MODULE-PATH --module-path MP --limit-modules java.base`

This jlink command should fail as `jdk.net` required by `b` is not observable.

> Note that one pre-existing test case verifies case (2) above. It asserts that the modules in the image only include the transitive closure of `b` (not including `a`, `c`). This would then change to also include `a` and `c`.

Yes, I'm aware of that and needs discussion.

> A corollary of it would be that if the module path includes the `jmods` folder, it would always include all JDK modules plus any that are observable outside that set without any means to cut the list of included modules.

JDK modules are not on `--module-path` by default.  So they will not be included.   If `--module-path $JAVA_HOME/jmods` is specified with `--add-modules ALL-MODULE-PATH`, it explicitly requests to add all packaged modules from `jmods` directory.

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PR Comment: https://git.openjdk.org/jdk/pull/22494#issuecomment-2549780804