META-INF is not changed when file is removed

[MrKuip]

I use @IndexSubclasses on the interface ExtensionIF.
I created a file Ext1 that subclasses ExtensionIF.
I created a file Ext2 that subclasses ExtensionIF.

The method ClassIndex.getSubclasses(ExtensionIF.class) returns Ext1 and Ext2. This is good!
The method ServiceLoader.load(ExtensionIF.class) returns Ext1@1 and Ext2@2. This is good!

I now remove Ext2.

The method ClassIndex.getSubclasses(ExtensionIF.class) returns Ext1. This is good!
The method ServiceLoader.load(ExtensionIF.class) exits with an exception:
Exception in thread "main" java.util.ServiceConfigurationError: gti.extension.ExtensionIF: Provider gti.extension.Ext2 not found
at java.util.ServiceLoader.fail(ServiceLoader.java:239)
at java.util.ServiceLoader.access$300(ServiceLoader.java:185)
at java.util.ServiceLoader$LazyIterator.nextService(ServiceLoader.java:372)
at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:404)
at java.util.ServiceLoader$1.next(ServiceLoader.java:480)
at Test.main(Test.java:17)

It seems that the file META-INF/services/gti.extension.ExtensionIF is not changed when I remove
a file. Is this is a bug? Is it fixable?

[sentinelt]

This problem manifests itself only during incremental compilation. I looked at this few years ago. The annotation processor was executed only when the class is recompiled, but I had not found any way to be notified when it is removed. ClassIndex.getSubclasses has a workaround for that - it simply ignores classes that do not exist at run-time.

I will look into this issue once again to check if there are some new ways to detect that.

[MrKuip]

You are right the problem manifest itself when compiling incrementally. But it would be nice if that worked also.

Here is another problem:

• I remove the @IndexSubclasses annotation from ExtenstionIF
• The method ClassIndex.getSubclasses(ExtensionIF.class) returns Ext1 and Ext2. This is wrong!
• The method ServiceLoader.load(ExtensionIF.class) returns Ext1@1 and Ext2@2. This is wrong!

[MrKuip]

Is this a solution?

• Validate all entries in the generated files just before writing the file?
• All entries that are not validated are removed
• If a file has no more entries than that file is removed

Mind you, You have to know ALL the files that have been created in the past

[sentinelt]

I would need to verify this, but I believe annotation processor does not always have an access to all of the classes processed in the past.