8287186: JDK modules participating in preview

[PaulSandoz]

Allow JDK modules that use preview features (preview language features or preview API features from dependent modules) to participate without the need to compile with --enable-preview.

It's difficult to enable participation using an annotation due to the nature in which symbols are encountered when processing source as there is no guaranteed order to the processing of certain symbols.

Instead a JDK module participates if the java.base package jdk.internal.javac is exported to that module (@lahodaj clever idea!). An internal annotation jdk.internal.javac.ParticipatesInPreview can be declared on the module. Such a declaration cannot be enforced but does by its use require the jdk.internal.javac's export list to be updated.

The modules jdk.incubator.vector and jdk.incubator.concurrent have been updated accordingly, both of which participate in preview APIs (APIs in java.lang.foreign and Thread.ofVirtual, respectively).

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue

Issue

• JDK-8287186: JDK modules participating in preview

Reviewers

• Alan Bateman (@AlanBateman - Reviewer) ⚠️ Review applies to 9defdf23
• Jan Lahoda (@lahodaj - Reviewer) ⚠️ Review applies to 9defdf23

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk pull/9087/head

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[bridgekeeper]

👋 Welcome back psandoz! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@PaulSandoz The following labels will be automatically applied to this pull request:

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[mlbridge]

Webrevs

• 03: Full - Incremental (810fe5d3)
• 02: Full - Incremental (abd1fbf6)
• 01: Full - Incremental (9defdf23)
• 00: Full (5e7ca855)

[AlanBateman]

Can java.management participate too? It would allow sun.management.Util.isVirtual(Thread) to go away (lots of methods in sun.management.ThreadImpl need to test if a thread is virtual).

[PaulSandoz]

Can java.management participate too? It would allow sun.management.Util.isVirtual(Thread) to go away (lots of methods in sun.management.ThreadImpl need to test if a thread is virtual).

Pushed update.

[AlanBateman]

The updates to java.base, java.management, and jdk.incubator.* looks fine, it's good to have the reflection code go away.

[openjdk]

@PaulSandoz This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8287186: JDK modules participating in preview

Reviewed-by: alanb, jlahoda

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 4 new commits pushed to the master branch:

• 53a0ace: 8286101: Support formatting in @value tag
• 8f400b9: 8286779: javax.crypto.CryptoPolicyParser#isConsistent always returns 'true'
• e0baf01: 8287007: [cgroups] Consistently use stringStream throughout parsing code
• 1769596: 8285263: Minor cleanup could be done in java.security

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[lahodaj]

javac + jdk.internal.javac changes look good to me.

[liach]

Just curious, is it still up to incubator modules' discretion to avoid accidental user access to preview content via the modules without enabling preview, like the PreviewFeatures.ensureEnabled() in StructuredTaskScope?

[PaulSandoz]

/integrate

[openjdk]

Going to push as commit fb29770.
Since your change was applied there have been 18 commits pushed to the master branch:

• 0530f4e: 8288094: cleanup old _MSC_VER handling
• 1a65332: 8287906: Rewrite of GitHub Actions (GHA) sanity tests
• c2ccf4c: 8288003: log events for os::dll_unload
• 03dca56: 8287525: Extend IR annotation with new options to test specific target feature.
• 86c9241: 8287028: AArch64: [vectorapi] Backend implementation of VectorMask.fromLong with SVE2
• fbe9266: 8288378: [BACKOUT] DST not applying properly with zone id offset set with TZ env variable
• 1904353: Merge
• 7aafc69: 8288105: [PPC64] Problems with -XX:+VerifyStack
• f4b05a1: 8288173: JDK-8202449 fix causes conformance test failure : api/java_util/Random/RandomGenerator/NextFloat.html
• d9c1364: 8288101: False build warning-as-error with GCC 9 after JDK-8214976
• ... and 8 more: https://git.openjdk.org/jdk/compare/b97a4f6cdcd5e497ab901e68923666e493414825...master

Your commit was automatically rebased without conflicts.

[openjdk]

@PaulSandoz Pushed as commit fb29770.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[PaulSandoz]

@liach it depends on the API and its scope. A constructor of StructuredTaskScope specifies that it implicitly uses a virtual thread factory, so it performs a preview runtime check.

The same check is also performed by Thread.ofVirtual, ensuring developers cannot reflectively work around
--enable-preview when creating virtual threads. This approach is feasible since the API surface is so small.