WG - Gizmo 2

[mkouba]

Objective:

The main objective of this working group is to make the Gizmo 2 POC production-ready and integrate it into Quarkus.

The Problem

Gizmo1 has many limitations:

• It is built on top of ASM (which is considered obsolete by the OpenJDK team)
• The output (the generated bytecode) is not optimized
• The API is not exactly concise and readable
• It's not possible to implement some Java constructs, such as try-finally block
• ...

The proposed Solution

• Gizmo 2 is built on top of java.lang.classfile API, introduced in Java 24+ (JEP 484).
  • Tightly integrates with the JDK and JVM at all levels
• We will need to use the jdk-classfile-backport project for JDK 17+
• The API aims to be readable and clean
• Gizmo 2 should cover all use cases solved by Gizmo 1
• The plan is to support both versions for a specific period of time to get more feedback and provide a smooth migration path for Gizmo 1 users (extension developers)

Definition of Done

• Deliver a stable version of Gizmo 2, fully integrated in Quarkus
• Create a new "bytecode generation" guide for extension developers
• Write a blog post, contribute a Quarkus insights

Scope of Work

It is out of scope to migrate all existing Gizmo 1 code in Quarkus core to Gizmo 2.
It is also out of scope to deprecate and remove Gizmo 1 from Quarkus.

Organizing the Work

Communication and Transparency:

Coordination will be done in the relevant project's GitHub issues.
Most of the work will be done in Quarkus core and the Gizmo project repository.

Point of Contact:

Point of Contact: Martin Kouba

Expected Timeline:

• Milestone 1 - release a "usable" Beta of Gizmo2; this release should include a reasonable test coverage and complete API
• Milestone 2 - initial integration work in Quarkus
• Milestone 3 - migrate selected extensions to Gizmo 2; this would potentially trigger another Beta releases, API updates, etc.

[dmlloyd]

I can do an alpha tag now to start the ball rolling. (Edit: this is complete (thanks @gsmet) and 2.0.alpha1 is released)