RFR: 8290041: ModuleDescriptor.hashCode is inconsistent [v2]

[Alan Bateman]

On Thu, 11 Aug 2022 14:16:51 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> Can I please get a review of this change which proposes to fix https://bugs.openjdk.org/browse/JDK-8290041? 
>> 
>> As noted by the reporter, the current implementation is buggy since the calculation can result in a different value of the hashcode depending on the order of iteration of the `Modifier`s. The commit in this PR changes that computation to produce consistent result irrespective of the order in which the `Modifier`s (enum) is iterated upon.
>> 
>> A new test has been added which reproduces the issue and verifies the fix.
>
> Jaikiran Pai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   incorporate review comments and add more testing

src/java.base/share/classes/java/lang/module/ModuleDescriptor.java line 2630:

> 2628:         int h = 0;
> 2629:         for (Enum<?> e : enums) {
> 2630:             h += e.name().hashCode();

Good

test/jdk/java/lang/module/ModuleDescriptorHashCodeTest.java line 83:

> 81:         final Set<ModuleDescriptor.Opens.Modifier> mods2 = Set.of(
> 82:                 ModuleDescriptor.Opens.Modifier.MANDATED, ModuleDescriptor.Opens.Modifier.SYNTHETIC);
> 83:         final ModuleDescriptor desc2 = createModuleDescriptor(mods2, null, null);

If you import Requires, Exports and Opens then it should mean you can fit these onto a single line and might be easier to read, e.g.

var mods2 = Set.of(Opens.Modifier.MANDATED, Opens.Modifier.SYNTHETIC);

test/jdk/java/lang/module/ModuleDescriptorHashCodeTest.java line 181:

> 179:             Set<ModuleDescriptor.Exports.Modifier> expsModifiers) {
> 180: 
> 181:         final var mdb = ModuleDescriptor.newModule("foobar");

Does "mdb" stand for something here?

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PR: https://git.openjdk.org/jdk/pull/9790