JDK-8285939: javadoc java.lang.Record should not have "Direct Known Subclasses:" section

[jonathan-gibbons]

As described in the JBS issue, the observed problem is a side-effect of a related but different issue, which is that record classes are not treated the same was as enum classes when it comes to generating the class hierarchy in ClassTree. Because record classes are not treated specially/differently, they are treated as ordinary/plain classes, with the side-effect that the page for java.lang.Record shows Direct Known Subclasses.

The underlying fix is therefore to clone the enum support in ClassTree and related classes, to provide support for record classes. It is possible to do an extreme minimal clone, but that just clones some of the messy evolution already there. Instead, the code in ClassTree and its clients is refactored and modernized.

Previously there were four explicit pairs of member fields, containing data for different groups (hierarchies) of classes, namely: plain classes, enum classes, interfaces and annotation interfaces. These fields are most of the code to support them are moved into some new abstractions to encapsulate related functionality.

1. The main new abstraction in ClassTree is Hierarchy which provides the support for the different hierarchies displayed in the generated pages.
2. A new enum HierarchyKind identifies the four existing hierarchies (listed above) and now a new one, for record classes. The hierarchies correspond to the different kinds of declared type.
3. A small new class SubtypeMap which is a multi-map for mapping a type element to its subtypes. This is used in Hierarchy and to record the classes that implement an interfaces.

Generally, the naming should be clearer and more obvious. The most confusing name in the old code was enumSubtypes which was weird because enum classes don't have subtypes. It meant "subtypes of supertypes of enum classes". This was a prime motivator to switch to the hierarchy terminology. The variant spellings of intfacs have all been replaced by interfaces, and classtree becomes classTree.

Testing: a new test case has been added to the TestRecordTypes.java test, which verifies the new record hierarchy is displayed on a a package tree page. It is not simple to directly test the observed/reported behavior, because it is specific to the JDK API documentation, and because it is about the content of the java.lang.Record API page. However, manual inspection and diff comparison between JDK API documentation generated before and after this change reveals only expected differences. These differences are on the java.lang.R4cord page (where the offending section is no longer displayed) and on the pages related to the two existing records in JDK ... which are now listed in Record Class Hierarchy sections in the appropriate package-tree.html files.

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Issue

• JDK-8285939: javadoc java.lang.Record should not have "Direct Known Subclasses:" section

Reviewers

• Pavel Rappo (@pavelrappo - Reviewer) ⚠️ Review applies to a4d52be4
• Hannes Wallnöfer (@hns - Reviewer) ⚠️ Review applies to c8ec372f

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[openjdk]

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Webrevs

• 03: Full - Incremental (b9b62dd1)
• 02: Full (a4d52be4)
• 01: Full (c8ec372f)
• 00: Full (a6460c01)

[pavelrappo]

Although I haven't looked into code in detail, I can confirm that the following JDK API pages have been updated and look good:

1. java.base/java/lang/Record.html
2. java.base/java/lang/class-use/Object.html
3. java.base/java/lang/class-use/Record.html
4. java.base/java/lang/package-use.html
5. jdk.jshell/jdk/jshell/package-tree.html
6. jdk.net/jdk/net/package-tree.html
7. overview-tree.html

WRT documentation, a hierarchy of records now behave similarly to that of enums.

[pavelrappo]

Please merge this branch with the master (they are now in conflict) and I will review the change.

[hns]

This is a nice cleanup! My only objection is that some refactored/moved methods have lost their doc comment.

[openjdk]

@jonathan-gibbons 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:

8285939: javadoc java.lang.Record should not have "Direct Known Subclasses:" section

Reviewed-by: prappo, hannesw

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 60 new commits pushed to the master branch:

• f5bbade: 8287544: Replace uses of StringBuffer with StringBuilder in java.naming
• 97bd4c2: 8286159: Memory leak in getAllConfigs of awt_GraphicsEnv.c:585
• 8db5247: 8282771: Create test case for JDK-8262981
• cfdbde1: 8282778: Create a regression test for JDK-4699544
• 8df5f10: 8282857: Create a regression test for JDK-4702690
• e0382c5: 8285401: Proxy class initializer should use 3-arg Class.forName to avoid unnecessary class initialization
• 37a5130: 8287064: Modernize ProxyGenerator.PrimitiveTypeInfo
• d5b6c7b: 8287384: Speed up jdk.test.lib.util.ForceGC
• 6f6486e: 8284960: Integration of JEP 426: Vector API (Fourth Incubator)
• 171a7cd: 8286895: InternalError: Exception during analyze
• ... and 50 more: https://git.openjdk.java.net/jdk/compare/3d6d7b7e7371dad3bd0983a9e26c39261783dcb4...master

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.

[pavelrappo]

Looks good.

[jonathan-gibbons]

/integrate

[openjdk]

Going to push as commit 8fc201e.
Since your change was applied there have been 60 commits pushed to the master branch:

• f5bbade: 8287544: Replace uses of StringBuffer with StringBuilder in java.naming
• 97bd4c2: 8286159: Memory leak in getAllConfigs of awt_GraphicsEnv.c:585
• 8db5247: 8282771: Create test case for JDK-8262981
• cfdbde1: 8282778: Create a regression test for JDK-4699544
• 8df5f10: 8282857: Create a regression test for JDK-4702690
• e0382c5: 8285401: Proxy class initializer should use 3-arg Class.forName to avoid unnecessary class initialization
• 37a5130: 8287064: Modernize ProxyGenerator.PrimitiveTypeInfo
• d5b6c7b: 8287384: Speed up jdk.test.lib.util.ForceGC
• 6f6486e: 8284960: Integration of JEP 426: Vector API (Fourth Incubator)
• 171a7cd: 8286895: InternalError: Exception during analyze
• ... and 50 more: https://git.openjdk.java.net/jdk/compare/3d6d7b7e7371dad3bd0983a9e26c39261783dcb4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@jonathan-gibbons Pushed as commit 8fc201e.

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