On Wed, 2 Dec 2020 19:31:59 GMT, Dan Smith <dlsm...@openjdk.org> wrote:
>>> Additional changes may be needed to Class.permittedSubclasses() and/or >>> Class.isSealed() as part of fixing bug JDK-8256867. The JVM is being >>> changed to treat classes with empty PermittedSubclasses attributes as >>> sealed classes that cannot be extended (or implemented). >>> >>> Current thinking is that Class.permittedSubclasses() will return an empty >>> array for both non-sealed classes and for sealed classes with empty >>> PermittedSubclasses attributes. And, Class.isSealed() will return False in >>> the former case and True in the latter. This will require changing the >>> implementation of Class.isSealed() to call the JVM directly instead of >>> calling Class.permittedSubclasses(). >>> >>> Does this seem like a reasonable way to handle this corner case? >> >> I suggest `Class::getPermittedSubclasses` to return a `non-null` array if >> this `Class` is sealed, i.e. this class is derived from a `class` file with >> the presence of `PermittedSubclasses` attribute regardless of its content >> (the attribute could be empty or contains zero or more entries which is a >> properly loaded permitted subtype. >> >> If this `Class` is not sealed, `Class::getPermittedSubclasses` returns null >> (see `Class::getRecordComponents` and some other reflection APIs as >> precedence). > >> I suggest `Class::getPermittedSubclasses` to return a `non-null` array if >> this `Class` is sealed, i.e. this class is derived from a `class` file with >> the presence of `PermittedSubclasses` attribute regardless of its content >> (the attribute could be empty or contains zero or more entries which is a >> properly loaded permitted subtype. >> >> If this `Class` is not sealed, `Class::getPermittedSubclasses` returns null >> (see `Class::getRecordComponents` and some other reflection APIs as >> precedence). > > Agree, that seems reasonable. Often, methods in `Class` with an array return > type default to an empty array, but `getRecordComponents` is a good example > of returning `null` when an empty array is meaningful. I've changed Class.getPermittedSubclasses to return null for classes that are not sealed here: https://github.com/openjdk/jdk/pull/1483/commits/7056143822ff62dfbb1d294c67352ed3892317c2 with follow-up changes to tests here: https://github.com/openjdk/jdk/pull/1483/commits/537e267fb6802ab5cf38bf26978039383cc6309a How does this look? ------------- PR: https://git.openjdk.java.net/jdk/pull/1483
