Add 4-arg map override to FilterFileChannel

[mayya-sharipova]

Java 22 added FileChannel.map(MapMode, long, long, Arena) which
returns MemorySegment. The base FileChannel class provides a default
implementation that throws UnsupportedOperationException. Without
this override, any wrapped FileChannel based on FilterFileChannel
would fail when the 4-arg map variant is called.

[mayya-sharipova]

@ldematte would appreciate your review here

[ldematte]

The change looks good, it's the missing overload. However I'm not sure about one thing: this API is JDK 22+, and AFAIK lucene supports JDK 21. This could fail to compile (or at least give you warnings) with target 21, but most importantly it will fail at runtime if we run this with JDK 21. Again, not sure if this is an issue or not, especially since this is test code, but I wanted to point it out.

[dweiss]

AFAIK lucene supports JDK 21

Not on main, no. Main is jdk25+.

[ldematte]

Not on main, no. Main is jdk25+.

Oh nice! So I don't see any issue with this change.

[benwtrent]

Not on main, no. Main is jdk25+.

Yep, this just cannot be backported to 10x.

[uschindler]

Hi,
as the test-only file system provider now allows this (wasn't possible with Java 21 due to public API differences and preview state), the foillowing line should also be removed:

lucene/lucene/core/src/java/org/apache/lucene/store/MMapDirectory.java

Lines 325 to 326 in f7b35cb

	// Work around for JDK-8259028: we need to unwrap our test-only file system layers
	path = Unwrappable.unwrapAll(path);

This is no longer needed because the test-wrappers now behave correctly.

[uschindler]

Oh this was already resolved, can you do the change on main branch or should I?

[uschindler]

Here is the PR: #15804

Will merge when tests are done.

[uschindler]

Done.

[uschindler]

Basically this was my fault as I did not remove the MMapDirectory unwrapping after update to Java 22+ on main (see #14564, especially https://github.com/apache/lucene/pull/14564/changes#diff-8681a7b2259f78a6d0d2efe4894ef79ce4697c3825d24675248bc557617773ceL58). If I would have removed it I would have noticed the missing override anyways. Note to myself: "When migrating code to later java versions check your TODOs and workarounds in source code!"