pjfanning opened a new pull request, #3720:
URL: https://github.com/apache/pekko/pull/3720
### Motivation
Java generics are invariant, so the javadsl APIs of the typed modules reject
pre-typed function values a Java user would reasonably pass, for example a
`Function<Object, Behavior<String>>` for `Behaviors.receiveMessage`, a handler
over `CharSequence` for `onMessage(String.class, ...)`, a `Function<Object,
String>` for `ActorContext.messageAdapter`, or a `BiFunction` over a supertype
of the state for an event sourced command handler. Lambdas adapt to the target
type; variables, fields and shared handlers do not.
#3713, #3714, #3717 and #3719 cover the stream javadsl and #3718 covers
stream-typed. This is the rest of item 3 in the follow-up comment on #3712.
### Modification
- Widen function-typed parameters (`japi.function`
`Function`/`Function2`/`Creator`/`Predicate`/`Procedure` and
`java.util.function`
`Function`/`BiFunction`/`Supplier`/`Consumer`/`BiConsumer`/`Predicate`) in the
javadsl of:
- **actor-typed**: `Behaviors` (`setup`, `receiveMessage`, `withTimers`,
`withStash`, `withMdc`, …), `BehaviorBuilder`/`ReceiveBuilder` handlers,
`ActorContext` (`messageAdapter`, `ask`, `askWithStatus`, `pipeToSelf`),
`AskPattern`, `Adapter.props`, `Routers`, `StashBuffer`
- **actor-testkit-typed**: `TestProbe` (`fishForMessage`, `awaitAssert`,
`within`), `LoggingTestKit`, `BehaviorTestKit.runAsk*`
- **cluster-typed**: `ReplicatorMessageAdapter`, `DistributedData`
- **cluster-sharding-typed**: `ClusterSharding`/`EntityRef.ask`,
`ShardedDaemonProcess`
- **persistence-typed**: command/event/signal handler builders (classic
and durable state), `Effect` `thenRun`/`thenReply`, `ReplicatedEventSourcing`
- **persistence-testkit**: `EventSourcedBehaviorTestKit`,
`DurableStateBehaviorTestKit`
- Inputs take `? >:` and results `? <:`; no bound is added where it cannot
widen anything (e.g. `? <:` on `Boolean` or `String`).
- Only final classes, objects and `@DoNotInherit` types are changed, so no
user subclass or override can break; Pekko's internal implementations are
updated to match. Deliberately **not** changed because users or plugins
implement them: the classic `testkit` `TestKit` and `EventFilter`,
`coordination` `Lease`, and the persistence-query `@ApiMayChange` query traits
(and `EventsBySliceFirehoseQuery`, which implements one of them).
- The persistence-typed handler builders keep their internal invariant
storage; widened handlers and predicates are narrowed where they are stored,
and Scala lambdas passed to the overloaded `onCommand`/`onEvent` get explicit
types so Scala 2 overload resolution still works.
- Add MiMa excludes (`IncompatibleSignatureProblem` only) per module.
### Result
Java callers can pass function values typed over a supertype of the input or
a subtype of the result without casts. Erasure is unchanged, so the change is
binary compatible.
### Tests
- New directional tests that only compile with the widened signatures:
`FunctionWildcardBoundsTest` (actor-typed-tests: `receiveMessage`,
`BehaviorBuilder.onMessage`, `messageAdapter`, `TestProbe.fishForMessage`) and
`EventSourcedBehaviorJavaDslTest.acceptHandlersTypedOverSupertypes`
(`onAnyCommand`, `onAnyEvent`, `thenRun`). Not run locally - left to CI.
- `sbt compile` for the changed modules on Scala 2.13 and `++3.3.8` - passed
- `sbt Test/compile` for `actor-typed-tests`, `actor-testkit-typed`,
`cluster-typed`, `cluster-sharding-typed`, `persistence-typed`,
`persistence-typed-tests`, `persistence-testkit` (Scala 2.13) - passed
- `sbt mimaReportBinaryIssues` for the changed modules - passed with the
added excludes
- `docs` and Scala 3 test compilation left to CI
### References
Refs #3712, #3718
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