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chore: remove leftover Scala 2.12 idioms - #3539

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chore: remove leftover Scala 2.12 idioms#3539
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pjfanning:scala-2.13-idioms

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@pjfanning pjfanning commented Sep 12, 2026 •
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Motivation

The codebase still carried a number of Scala 2.12-era idioms that are redundant or deprecated on Scala 2.13/3: immutable.Seq qualifiers (scala.Seq has been immutable.Seq since 2.13), the deprecated mutable.WrappedArray alias, filterKeys/mapValues on Map, Either left/right projections, and .toIterator/Stream in user-facing doc snippets.

Modification

  • Replace immutable.Seq with Seq across ~210 files and drop the now-unused scala.collection.immutable imports. scala.Seq is a type alias for scala.collection.immutable.Seq on 2.13 and 3, so this is source- and binary-compatible (same erasure). DslFactoriesConsistencySpec is left as-is since it deliberately distinguishes collection.Seq from immutable.Seq.
  • ByteStringBuilder.addAll: match mutable.ArraySeq.ofByte and immutable.ArraySeq.ofByte instead of the deprecated WrappedArray.ofByte. Array.toSeq/toIndexedSeq produce immutable.ArraySeq.ofByte on 2.13, which previously fell through to the generic path.
  • Remove a dead commented-out CanBuildFrom block in ByteString.
  • ManifestInfo: replace deprecated filterKeys (and its @nowarn) with filter.
  • ShardRegion scaladoc example: filterKeys -> filter.
  • Rendered doc snippets: Source(Stream.from(1)) -> Source(LazyList.from(1)) (KillSwitchDocSpec), buffer.toIterator -> buffer.iterator (GraphStageDocSpec).
  • Tests: Shrink.withLazyList instead of Shrink(_ => Stream.empty), view.mapValues instead of a @nowarn wrapper, .iterator instead of .toIterator, and plain Either equality instead of .left.get/.right.get (dropping the @nowarn on MetricNumericConverterSpec).
  • Paradox docs: prose and @apidoc scala anchors updated from immutable.Seq to Seq to match the regenerated scaladoc ids (all 25 Seq-bearing anchors verified against stream/doc output); four anchors that were already broken on main were corrected while touching them.
  • MiMa: one IncompatibleSignatureProblem filter for Shape.hasOnePort (@InternalApi private[pekko]): erased descriptor is unchanged, only the Java generic signature moved from Seq<?> to Seq<Object>.

The 2.12 branches in project/PekkoDisciplinePlugin.scala and the filterKeys/mapValues uses under project/ (sbt still runs on 2.12) are intentionally left unchanged.

Result

No remaining Scala 2.12 collection idioms in main, test or doc sources.

Tests

  • native scalafmt run on all changed files
  • sbt stream/mimaReportBinaryIssues passes locally with the filter
  • sbt stream/doc generated and used to verify the paradox anchors
  • full Test/compile and tests: relying on CI

References

None - Scala 2.12 support was dropped previously

@pjfanning
chore: remove leftover Scala 2.12 idioms
b737f63 
Motivation:
The codebase still carried a number of Scala 2.12-era idioms that are
redundant or deprecated on Scala 2.13/3: `immutable.Seq` qualifiers
(`scala.Seq` has been `immutable.Seq` since 2.13), the deprecated
`mutable.WrappedArray` alias, `filterKeys`/`mapValues` on `Map`,
`Either` left/right projections, `.toIterator` and `Stream` in
user-facing doc snippets.

Modification:
- Replace `immutable.Seq` with `Seq` and drop the now-unused
  `scala.collection.immutable` imports (same erasure, binary compatible).
- `ByteStringBuilder.addAll`: match `mutable.ArraySeq.ofByte` and
  `immutable.ArraySeq.ofByte` instead of the deprecated
  `WrappedArray.ofByte`; the immutable case previously fell through to
  the generic path.
- Remove a dead commented-out `CanBuildFrom` block in `ByteString`.
- `ManifestInfo`: replace deprecated `filterKeys` with `filter`.
- `ShardRegion` scaladoc example: `filterKeys` -> `filter`.
- Doc snippets: `Stream.from(1)` -> `LazyList.from(1)`,
  `buffer.toIterator` -> `buffer.iterator`.
- Tests: `Shrink.withLazyList`, `view.mapValues`, `.iterator`, and
  plain `Either` equality instead of `.left.get`/`.right.get`.

Result:
No remaining 2.12 collection idioms in source and doc code. Build
definition under `project/` is intentionally left unchanged.

Tests:
- native scalafmt run on changed files
- sbt Test/compile, multi-jvm:compile in progress; relying on CI

References:
None - Scala 2.12 support was dropped previously
@pjfanning
chore: remove unused immutable imports flagged by CI
a7bde82
@pjfanning
pjfanning marked this pull request as draft September 12, 2026 02:05
@pjfanning
chore: add MiMa filter for Shape.hasOnePort generic signature change
01a7040
@pjfanning
docs: update paradox references and apidoc anchors for immutable.Seq …
52467af 
…-> Seq

Scaladoc now renders the rewritten signatures as `Seq[...]`, so the
`@apidoc` scala anchors in the stream operator pages no longer matched
the generated ids. Also fixes a few anchors that were already wrong
(missing `[T]`, `,M` vs `_`, short vs qualified names, and
`mergePrioritizedN` pointing at `Source` instead of `Source$`).
@pjfanning
docs: fix javadoc anchor for mergePrioritizedN
7b40a40
@pjfanning
pjfanning marked this pull request as ready for review September 12, 2026 08:20
This was referenced Sep 12, 2026
Merged
Merged
pjfanning added a commit to apache/pekko-http that referenced this pull request Sep 12, 2026
@pjfanning
chore: replace immutable.Seq with Seq, drop Scala 2.12-era imports (#…
f019432 
…1298)

Motivation:
The codebase still carried the Scala 2.12-era `immutable.Seq` qualifier
across ~100 files. `scala.Seq` has been an alias for
`scala.collection.immutable.Seq` since 2.13, so the qualifier and the
`scala.collection.immutable` imports that only exist to support it are
redundant. Mirrors apache/pekko#3539.

Modification:
- Replace `immutable.Seq`, `collection.immutable.Seq` and
  `scala.collection.immutable.Seq` with `Seq` in main, test, multi-jvm
  and docs-snippet Scala sources.
- Drop `import scala.collection.immutable` / `immutable.Seq` where no
  other `immutable.*` member is used; keep it where TreeMap,
  VectorBuilder, ListMap, etc. are still referenced.
- `Http2Blueprint`: `import scala.collection.{ immutable, mutable }` ->
  `import scala.collection.mutable`.
- Paradox docs: prose and signature mentions updated from
  `immutable.Seq` to `Seq`; `alphabetically.md` table rows re-padded.
- Java sources are unchanged: `scala.Seq` is a package-object alias
  that Java cannot name.

Result:
No remaining `immutable.Seq` idioms in Scala sources or docs. Source-
and binary-compatible (same erasure); no MiMa filter needed.

Tests:
- native scalafmt 3.7.17 on all changed Scala files
- sbt Test/compile multi-jvm:compile (Scala 2.13.18)
- sbt http-core/mimaReportBinaryIssues http/mimaReportBinaryIssues
  http-cors/mimaReportBinaryIssues http-xml/mimaReportBinaryIssues
- sbt http-cors/test; HeaderSpec, HttpHeaderSpec, FramingSpec,
  Http2FramingSpec, HttpMessageRenderingSpec, Http*DetailedStringExampleSpec

References:
None - follows apache/pekko#3539
@pjfanning pjfanning mentioned this pull request Sep 12, 2026
Merged
pjfanning added a commit to apache/pekko-management that referenced this pull request Sep 12, 2026
@pjfanning
chore: remove leftover Scala 2.12 idioms (#970)
44e6270 
Motivation:
The codebase still carried the Scala 2.12-era immutable.Seq qualifier
(and its scala.collection.immutable / immutable.Seq imports). On Scala
2.13 and 3, scala.Seq is already an alias for
scala.collection.immutable.Seq, so the qualifier is redundant.

Modification:
Replace immutable.Seq with Seq across 24 files and drop the now-unused
scala.collection.immutable, scala.collection.immutable.Seq and
scala.collection.{ immutable => im } imports. Files that still use other
immutable.* types (Set, Iterable, SortedSet) keep the import.
ClusterHttpManagementRoutesSpec swaps its scala.collection.immutable._
wildcard for an explicit SortedSet import. ConsulServiceDiscovery drops
a redundant scala.collection.immutable.Seq(targets: _*) copy since
targets is already an immutable Seq.

Result:
No remaining Scala 2.12 collection idioms in main or test sources.
Source- and binary-compatible: same erasure, MiMa passes unchanged.

Tests:
- native scalafmt --mode diff-ref=upstream/main
- sbt +Test/compile (Scala 2.13, 3.3, 3.next) passes
- sbt mimaReportBinaryIssues on all touched modules passes
- sbt test on all touched modules passes (ConsulDiscoverySpec not run:
  requires Docker/testcontainers locally)

References:
None - equivalent of apache/pekko#3539
This was referenced Sep 12, 2026
Open
Merged
Merged
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Merged
Merged
pjfanning added a commit to apache/pekko-connectors-kafka that referenced this pull request Sep 13, 2026
@pjfanning
Replace immutable.Seq with Seq (#655)
28ccd8d 
Motivation:
The codebase still carried Scala 2.12-era `immutable.Seq` qualifiers.
Since Scala 2.13, `scala.Seq` is a type alias for
`scala.collection.immutable.Seq`, so the qualifier is redundant.
Equivalent of apache/pekko#3539.

Modification:
- Replace `immutable.Seq` with `Seq` in main, testkit, test and doc
  sources and drop the now-unused `scala.collection.immutable` imports.
- Files that still use other `immutable.*` types keep the import.

Result:
No remaining `immutable.Seq` qualifiers. Source and binary compatible:
`Seq` erases to the same `scala.collection.immutable.Seq` class.

Tests:
- native `scalafmt` run on all changed files (no changes)
- `sbt Test/compile` passes
- `sbt core/mimaReportBinaryIssues testkit/mimaReportBinaryIssues` pass
- `sbt "tests/testOnly ...CommittingProducerSinkSpec ...ConsumerSpec"` pass

References:
None - Scala 2.12 support was dropped previously; port of apache/pekko#3539
pjfanning added a commit to apache/pekko-persistence-jdbc that referenced this pull request Sep 13, 2026
@pjfanning
Remove redundant Scala 2.12-era immutable.Seq imports (#617)
9d93fbf 
Motivation:
Since Scala 2.13, `scala.Seq` is a type alias for
`scala.collection.immutable.Seq`, and `Set`, `Vector`, `Nil` and
friends in the `scala` package already refer to the immutable
collections. The `scala.collection.immutable` imports and
`immutable.Seq` qualifiers carried over from the Scala 2.12 days are
therefore redundant now that this project only builds on 2.13 and 3.
This is the pekko-persistence-jdbc counterpart of apache/pekko#3539.

Modification:
- Drop the now-unused `scala.collection.immutable` imports
  (`immutable._`, `immutable.Seq`, `immutable.Set`,
  `immutable.{ Nil, Seq }`, `immutable.{ Seq, Vector }`).
- Replace `immutable.Seq` / `scala.collection.immutable.Seq` with
  plain `Seq`.
- `MissingElements` keeps its `immutable.NumericRange` import since
  `NumericRange` is not aliased in `scala._`.

`scala.Seq` erases to the same class, so the binary shape is unchanged.

Result:
No remaining Scala 2.12 collection idioms in main or test sources.

Tests:
- native `scalafmt --mode diff-ref=upstream/main`
- `sbt "+core/Test/compile"` on Scala 2.13.18, 3.3.8 and 3.9.0
- `sbt core/mimaReportBinaryIssues` passes (signature problems enabled)
- `sbt "core/Test/testOnly ...TrySeqTest ...BaseDaoSpec
  ...H2LimitWindowingStreamTest ...JdbcAsyncWriteJournalShutdownTest
  ...H2ScalaCurrentPersistenceIdsTest ...ByteArrayJournalSerializerTest"`:
  16 tests, all passed (H2)
- `git diff --check` clean

References:
Refs apache/pekko#3539
pjfanning added a commit to apache/pekko-persistence-cassandra that referenced this pull request Sep 13, 2026
@pjfanning
chore: remove leftover Scala 2.12 idioms (#498)
9ea9eb5 
Motivation:
The codebase still carried Scala 2.12-era `immutable.Seq` qualifiers,
which are redundant on Scala 2.13/3 where `scala.Seq` is already an
alias for `scala.collection.immutable.Seq`. Mirrors apache/pekko#3539.

Modification:
- Replace `immutable.Seq` with `Seq` and drop the now-unused
  `scala.collection.immutable` / `immutable.Seq` imports.
- `MultiNodeClusterSpec.assertLeader`: pass the varargs `Seq` straight
  through instead of `.to[immutable.Seq]`.
- `immutable.Iterable` in `CassandraReadJournal` and `immutable.Queue`
  in `AllPersistenceIdsStage` are left as-is (no `scala.` alias).

Result:
No remaining Scala 2.12 collection idioms in main, test or multi-jvm
sources. Same erasure, so source- and binary-compatible.

Tests:
- native `scalafmt --mode diff-ref=upstream/main`: clean
- `sbt "+core/Test/compile"` (2.13.18 and 3.3.8): passes after clean
- `sbt core/mimaReportBinaryIssues` on 2.13.18 and 3.3.8: no issues
- `sbt checkCodeStyle`: passes
- `core/MultiJvm/compile` already fails on `main` for unrelated reasons
  (missing `FlightRecordingSupport`, `CassandraContainer` type params)
- Cassandra-backed test suites not run locally (no Docker); relying on CI

References:
None - equivalent of apache/pekko#3539
pjfanning added a commit to apache/pekko-projection that referenced this pull request Sep 13, 2026
@pjfanning
chore: remove leftover Scala 2.12 idioms (#625)
18f73ba 
Motivation:
The codebase still carried the Scala 2.12-era `immutable.Seq` qualifier
throughout main, test and doc sources. `scala.Seq` has been an alias for
`scala.collection.immutable.Seq` since Scala 2.13, so the qualifier and the
`scala.collection.immutable` imports that exist only to support it are
redundant. This mirrors apache/pekko#3539.

Modification:
- Replace `immutable.Seq` with `Seq` across 37 Scala files and drop the
  `scala.collection.immutable` imports that are no longer referenced
  (kept where `immutable.IndexedSeq`/`immutable.Set` are still used).
- Drop the explicit `import scala.collection.immutable.Seq` lines.
- Paradox prose (cassandra, jdbc, r2dbc, slick) updated from
  `immutable.Seq` to `Seq` to match the doc snippets.

The other idioms addressed upstream (`WrappedArray`, `filterKeys`/
`mapValues`, `Either` projections, `toIterator`, `Stream`) do not occur in
this repository.

Result:
No remaining Scala 2.12 collection idioms in main, test or doc sources.
Source- and binary-compatible: same type, same erasure.

Tests:
- native `scalafmt --mode diff-ref=upstream/main` run on changed files
- `sbt Test/compile jdbc-int-test/Test/compile r2dbc-int-test/Test/compile slick-int-test/Test/compile` passes on Scala 2.13 and 3.3
- `sbt core/mimaReportBinaryIssues jdbc/mimaReportBinaryIssues slick/mimaReportBinaryIssues cassandra/mimaReportBinaryIssues eventsourced/mimaReportBinaryIssues durable-state/mimaReportBinaryIssues r2dbc/mimaReportBinaryIssues` passes (grpc has MiMa disabled)
- `git diff --check` clean

References:
None - mirrors apache/pekko#3539; Scala 2.12 support was dropped previously
pjfanning added a commit to apache/pekko-connectors that referenced this pull request Sep 13, 2026
@pjfanning
Chore: remove leftover Scala 2.12 immutable.Seq idioms (#1941)
2c2837b 
Motivation:
The codebase still qualified Seq as immutable.Seq throughout, a Scala
2.12-era habit. Since 2.13 (and on Scala 3) scala.Seq is an alias for
scala.collection.immutable.Seq, so the qualifier and the supporting
scala.collection.immutable imports are redundant. Mirrors apache/pekko#3539.

Modification:
- Replace immutable.Seq with Seq across 120 Scala files.
- Drop the now-unused scala.collection.immutable and
  scala.collection.immutable.Seq imports; reduce
  scala.collection.{ immutable, mutable } to scala.collection.mutable
  where only mutable remains in use.
- Keep scala.collection.immutable in files that still use
  immutable.Iterable, immutable.Map etc. immutable.Iterable is left
  unchanged because bare Iterable is scala.collection.Iterable.
- csv.md prose updated from immutable.Seq[String] to Seq[String].

Result:
No remaining immutable.Seq qualifiers in main, test or doc sources.
Types are identical (same erasure), so no API or binary change.

Tests:
- native scalafmt --mode diff-ref=origin/main
- sbt Test/compile (Scala 2.13.18) and sbt "++3.3.8" Test/compile
- sbt mimaReportBinaryIssues (all modules) passes, no filters needed
- sbt csv/test xml/test file/test text/test simple-codecs/test reference/test
- sbt docs/paradox

References:
None - follows apache/pekko#3539
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