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Posted to notifications@pekko.apache.org by "He-Pin (via GitHub)" <gi...@apache.org> on 2026/10/24 10:27:42 UTC
[PR] Add thenRun to staged reply effects [pekko]
He-Pin opened a new pull request, #3684:
URL: https://github.com/apache/pekko/pull/3684
### Motivation
A command handler can select between persisting and replying, replying without persistence, or explicitly not replying. After that decision, a caller cannot append a common callback through the staged reply-effect API introduced in #3682. Recording a metric or sending a notification requires duplicating the callback in each branch or moving it before the reply.
Add `thenRun` to that stage, while making `thenStop` end callback composition:
```scala
handleCommand(state, command)
.thenRun(updatedState => recordMetric(updatedState))
.thenStop()
```
The helper returns `ReplyEffectWithStop`. `thenStop().thenRun(...)` must not compile.
### Modification
- Declare `thenRun` on `ReplyEffectOps`, returning its recursive `Self` type: Scala's state callback and Java's state and no-argument overloads, for both event-sourced and durable-state persistence. Mark all new methods `@since 2.0.0`.
- Change `ReplyEffectWithStop.thenStop()` to return the base `ReplyEffect`. This rejects callbacks after stopping, including through `thenUnstashAll`, while `thenRun(...).thenUnstashAll().thenStop()` retains the expected stage. `stash()` continues to expose only the base type.
- Keep traits abstract and implement the Java overloads in `EffectImpl`. Make the existing Java `EffectBuilder.thenRun` methods overridable while retaining their bodies and descriptors. The existing subtype callback adaptation is reused; no effect downcasts or runtime stage checks are introduced.
- Add matching Scala and Java tests for persistence/reply/callback ordering, common callbacks after accepted and rejected branches, both no-reply entry points, generic `Self` helpers, and stopping after callbacks. Add compile-time rejection coverage for stopped, stashed, and widened effects.
- Update both persistence guides with the use case, type restrictions, and existing at-most-once side-effect guarantees. Sending a reply does not wait for the recipient to receive or process it.
### Result
Callers can append callbacks after choosing a reply without losing the ability to unstash or stop. Stopping the reply-effect chain removes callback capabilities. This adds no new trait and changes no runtime side-effect ordering; existing `EffectBuilder` chaining remains outside this reply-stage restriction.
**Stacked on #3682 at `c00fbb3376d47b8ec28abe151673207ec5f4e71e`.** The base branch `stack/3682-reply-effect-then-stop` mirrors that exact commit so this PR shows only the incremental change and runs upstream CI. Keep this PR in draft until the parent merges; then rebase and retarget to `main` before merging. Do not merge into the temporary stack base.
### Tests
- Isolated Scala 2.13 compilation of the eight effect API/implementation sources and all four new test files: passed.
- Scala and `javac` client probes: valid generic/fluent chains compile; 10 Scala and 20 Java invalid chains are rejected. Restoring the old `thenStop` return type makes the stopped-chain probes compile, demonstrating the regression check. Positive `thenRun` probes fail against the parent API as expected.
- Direct MiMa 1.2.1 probe against compiled `origin/main` sources: the same 22 findings covered by the parent's exact filters; no additional filter added. Published-baseline cross-version MiMa remains for CI.
- `scalafmt --mode diff-ref=c00fbb3376d47b8ec28abe151673207ec5f4e71e` and `--list`: passed.
- `sbt headerCreateAll javafmtAll` (JDK 17), followed by `sbt +headerCheckAll javafmtCheckAll checkCodeStyle`: passed.
- `sbt sortImports`: environment/tool linkage failure in `stream-tests` and `multi-node-testkit` (`scala.meta.package$.Input()`); unrelated generated edits removed. Subsequent code-style checks passed.
- `git diff --check`: passed. Auditable Qoder stdout review: no must-fix findings.
- Full runtime tests, Scala 3/next, `validatePullRequest`, published-baseline MiMa, and Paradox: delegated to remote CI; pending. No local full-suite runtime result claimed.
### References
Refs #3682, Refs #3683
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Re: [PR] Add thenRun to staged reply effects [pekko]
Posted by "He-Pin (via GitHub)" <gi...@apache.org>.
He-Pin commented on PR #3684:
URL: https://github.com/apache/pekko/pull/3684#issuecomment-6386827083
Will rebase on the main later
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Re: [PR] Add thenRun to staged reply effects [pekko]
Posted by "He-Pin (via GitHub)" <gi...@apache.org>.
He-Pin commented on PR #3684:
URL: https://github.com/apache/pekko/pull/3684#issuecomment-6387116849
@pjfanning Can you please take care of this one and I think this is the last one I want to be included in the 2.0.0 release.
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Re: [PR] Add thenRun to staged reply effects [pekko]
Posted by "He-Pin (via GitHub)" <gi...@apache.org>.
He-Pin closed pull request #3684: Add thenRun to staged reply effects
URL: https://github.com/apache/pekko/pull/3684
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Re: [PR] Add thenRun to staged reply effects [pekko]
Posted by "He-Pin (via GitHub)" <gi...@apache.org>.
He-Pin closed pull request #3684: Add thenRun to staged reply effects
URL: https://github.com/apache/pekko/pull/3684
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