Consider dropping Java 8 and 11 as Micronaut 4 baseline

sdelamo commented 2 years ago

Advantages

Use Latest Java Features

17 baseline for the framework allows us to take advantage of Java feature such as Java Records, Sealed Classes, Switch Expressions, Text Blocks, and Pattern matching for instanceof.

Use Java 17 features and code style in every guide

Currently, we have to write guides for Java 8 style.

Reduce CI Build times

Reduce our CI build matrix, decreasing build times and enhancing developer productivity.

Reducing the number of major versions supported

We may want to maintain each major version branch when we drop a Java version. Dropping both 8 and 11 may mean maintaing only two major branches until 2023 (next LTS).

In 2022 - Micronaut 3 with base Java 8 to 17. Micronaut 4 base 17. In 2023 - Micronaut 3 base 8 to 17. Micronaut 5 base 17 to 21.

If we drop JDK 8 in 4 and JDK 11 in 5, it may mean maintaining three branches.

In 2022 - Micronaut 3 with base Java 8 to 17. Micronaut 4 base 17. In 2023 - Micronaut 3 base 8 to 17. Micronaut 4 base 11 to 17. Micronaut 5 base 17 to 21. I don't think we can tell users in Micronaut 4 to "go back to 3 if you want to keep using 11 and be patched". That is the reason I list three branches in this scenario.

I have concerns about our capacity to maintain multiple major branches in core and modules.

Disadvantages

Dropping a JDK will keep some users running old versions of Micronaut

Any time we raise the baseline, it means some users will not be able to update to the latest version of the framework because they cannot update Java baseline for various reasons.

Some modules will have a minimum of Java 17

Supporting Micronaut Spring with Spring Boot 3 and Spring 6 requires a JDK 17 minimum. This is a situation which we have today. Some modules (for example, GCP) require a minimum of Java 11.