Add msgpack-jackson3 module for Jackson 3.x support

[komamitsu]

Summary

• Adds a new msgpack-jackson3 submodule (jackson-dataformat-msgpack3) that ports the existing Jackson 2.x integration to Jackson 3.x (tools.jackson namespace)
• Requires Java 17+ and Jackson 3.1.2; the module is excluded from the build on older JDKs so existing Java 8 users are unaffected
• Includes JMH benchmarks (src/jmh/java) runnable via ./sbt "msgpack-jackson3/jmh:run"
• Fixes Add Jackson 3 support #933

Key differences from msgpack-jackson

• Package namespace: com.fasterxml.jackson → tools.jackson
• TokenStreamLocation replaces JsonLocation; byte offset passed as columnNr
• Lightweight MessagePackWriteContext replaces SimpleStreamWriteContext

[Copilot]

Pull request overview

This PR adds a new msgpack-jackson3 submodule that ports the existing Jackson 2.x MessagePack integration to Jackson 3.x (tools.jackson namespace). It is published as a separate artifact (jackson-dataformat-msgpack-jackson3), requires Java 17+, and is conditionally included in the SBT build / CI / release pipelines so existing Java 8 users of msgpack-jackson are unaffected.

Changes:

• New msgpack-jackson3 module mirroring msgpack-jackson, adapted for Jackson 3 APIs (ObjectWriteContext/ObjectReadContext, TokenStreamLocation, ValueSerializer/ValueDeserializer, builder-style MapperBuilder/TSFBuilder, etc.) and including a lightweight MessagePackWriteContext replacement for SimpleStreamWriteContext.
• SBT build, CI workflow, and release workflow updated to compile/test/publish the new module only on JDK 17+, plus a new sbt-jmh plugin and JMH benchmarks under src/jmh/java.
• Numerous regression tests covering tricky edge cases (null keys, write-context state, dup-detection NPEs, root-scalar ordering, multi-root containers, writeNumber(String) NaN/Infinity, etc.).

Reviewed changes

Copilot reviewed 41 out of 42 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
build.sbt	Adds msgpack-jackson3 project, JMH plugin, Java 17 gating via isJava17Plus.
project/plugins.sbt	Adds sbt-jmh plugin.
.github/workflows/CI.yml	Skips msgpack-jackson3 tests on JDKs < 17.
.github/workflows/release.yml	Splits publishing so jackson3 is only published with JDK 17.
msgpack-jackson3/README.md	New documentation for the Jackson 3 module.
msgpack-jackson3/src/main/java/.../MessagePackFactory.java	Jackson 3 BinaryTSFactory implementation.
msgpack-jackson3/src/main/java/.../MessagePackFactoryBuilder.java	New TSFBuilder for the factory.
msgpack-jackson3/src/main/java/.../MessagePackGenerator.java	Port of generator; uses new MessagePackWriteContext, node-buffering model.
msgpack-jackson3/src/main/java/.../MessagePackParser.java	Port of parser to ParserMinimalBase; uses MessagePackReadContext.
msgpack-jackson3/src/main/java/.../MessagePackReadContext.java	Read context (replaces JsonReadContext).
msgpack-jackson3/src/main/java/.../MessagePackWriteContext.java	Lightweight write context.
msgpack-jackson3/src/main/java/.../MessagePackMapper.java	ObjectMapper subclass with new builder API.
msgpack-jackson3/src/main/java/.../MessagePackSerializerFactory.java	Custom serializer factory installing key serializer.
msgpack-jackson3/src/main/java/.../MessagePackSerializedString.java	SerializableString impl tolerant of null values.
msgpack-jackson3/src/main/java/.../MessagePackKeySerializer.java	Key serializer using MessagePackSerializedString.
msgpack-jackson3/src/main/java/.../MessagePackExtensionType.java	Extension type value + serializer.
msgpack-jackson3/src/main/java/.../ExtensionTypeCustomDeserializers.java	Per-type extension deserializer registry.
msgpack-jackson3/src/main/java/.../TimestampExtensionModule.java	Module serializing Instant as msgpack timestamp ext type.
msgpack-jackson3/src/main/java/.../JsonArrayFormat.java	AnnotationIntrospector forcing ARRAY shape.
msgpack-jackson3/src/main/java/.../PackageVersion.java	Hard-coded package version.
msgpack-jackson3/src/main/java/.../Tuple.java	Small Tuple helper.
msgpack-jackson3/src/test/java/...	Ported test suite plus new regression tests for Jackson 3 specific behavior.
msgpack-jackson3/src/jmh/java/...	New JMH benchmarks (read/write/UTF-8) and model classes.

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[komamitsu]

@xerial Can you take a quick look at the changes of .github/workflows/* and *.sbt?

[xerial]

@komamitsu Do you still need to maintain msgpack-jackson for Jackson 2.x? If we don't have critical use cases, I'll lean to dropping Jackson 2 support as supporting both Jackson2 and 3 will be overkill for msgpack-java project.

[xerial]

current usage: https://mvnrepository.com/artifact/org.msgpack/jackson-dataformat-msgpack/used-by

[komamitsu]

@xerial Jackson 2 is still actively used, and Jackson 3 requires Java 17+, so not everyone can migrate yet. I think we should support both for a while.

[komamitsu]

@hiSandog Good point. Addressed in 531d3d0

[komamitsu]

@xerial I addressed the conflict, PTAL.

BTW, it seems Universal Buffer Test has been skipped since #998 was merged.

[xerial]

@komamitsu Thank you for this PR — the Jackson 3 port itself looks solid, and I agree with your point that we should support both Jackson 2 and 3 for a while, since Jackson 3 requires Java 17+ and many users can't migrate yet.

Before merging, I'd like to propose restructuring the module naming. My concern with jackson-dataformat-msgpack3 is long-term: if Jackson 3 takes over Jackson 2 in the next couple of years, the unmarked name jackson-dataformat-msgpack will be stuck on the legacy version, and Jackson 3 users (the growing cohort) would eventually need a second migration from -msgpack3 back to the plain name. I'd rather put the clean name on the future from day one.

Concretely, I propose we cut msgpack-java 1.0.0 with this structure:

• jackson-dataformat-msgpack (1.x) = Jackson 3: your Jackson 3 code from this PR becomes the contents of the msgpack-jackson module. To avoid a classpath clash with the Jackson 2 artifact, the Java package moves to org.msgpack.jackson3.dataformat. Since Jackson 3 adopters are already rewriting every com.fasterxml.jackson import to tools.jackson, one more changed import costs them almost nothing — and it means both artifacts can coexist in one application for incremental migration (which was a design goal of Jackson's own tools.jackson rename).
• jackson2-dataformat-msgpack (1.x) = Jackson 2: the current msgpack-jackson code moves here unchanged, keeping the org.msgpack.jackson.dataformat package. Jackson 2 users who want to keep receiving msgpack-core updates only need a one-line artifactId change — no import changes at all. This module would be maintenance-mode (Jackson 2.x bumps and bug fixes only), documented as such in the README, to be dropped in a future major release when Jackson 2 usage fades.
• 0.9.x freezes: users who do nothing stay on jackson-dataformat-msgpack 0.9.10 and nothing breaks. We'll keep a 0.9.x branch as an escape hatch for critical fixes, but the plan is zero releases from it — this avoids maintaining two release lines with msgpack-core backports.

If dependabot/renovate proposes 0.9.x → 1.0.0 to a Jackson 2 user, it fails loudly at compile time (the old package is gone from that artifact), and the release notes will point to jackson2-dataformat-msgpack — so there's no silent breakage.

Since msgpack-java's API has been stable for a decade while sitting at 0.x, I think this transition is also the right occasion to finally signal 1.0.0.

Mechanically this reuses essentially all of your work — the Jackson 3 sources just land in msgpack-jackson with the package rename, and the JDK-conditional build exclusion you added carries over (the module still requires Java 17+ while msgpack-core and the Jackson 2 module stay on Java 8). The OSGi bundle symbolic names and export packages would be updated to match.

WDYT? If you're on board, I'm happy to help with the build.sbt / workflow changes for the restructuring.

[xerial]

I've opened #1012 implementing the restructuring proposed above, built on top of this PR's commits (so all the Jackson 3 port work is preserved and attributed). @komamitsu PTAL — if you prefer this direction we can continue the review there; if not, happy to discuss further here.

While enabling the module restructuring I also found that the Jackson 2 module's JUnit 5 tests have been silently skipped on main (no Jupiter test interface in the sbt build — likely related to the skipped Universal Buffer Test you noticed), and fixing that surfaced a small JsonLocation regression from #903. Both are fixed in #1012.