Move batch compiler to Java 17, drop Java 11 runtime support

[iloveeclipse]

See #886

The proposal is that with 4.28 release Eclipse Java Compiler (ECJ) will drop support for execution on Java runtime below 17, and will require at least Java 17 runtime for execution.

The reasons for switch to Java 17 runtime are:

• There are no tests running on Java 11 anymore. So we could have already broken ecj because of some runtime issue we don't see on Java 17 / 19.
• Use latest Java language features that simplify our life: records, instanceof pattern, etc in compiler code itself
• Use latest available JDK libraries, example: this one line using Java 17 was a complex method with 40 lines in Java 8!
• Simplify our life maintaining compiler source code configuration, build, test etc - all the jenkins/maven/github/ whatever configurations where we should simply reuse solutions we would have with default platform improvements we see every day.
• basically: save our time.
• Our development work would only benefit from Java 17.
• Consumers that need ecj running on Java 11 can use older ECJ versions.

The reasons for stay on Java 11 runtime are:

• First and foremost, Java 11 is still an active version that is still being supported by Oracle. Platform moving ahead is a complex case, but there's no such reason to do that in the batch compiler case.
• We should take a moment to think about all the ECJ consumers we will either be leaving behind or upsetting. Case in point, the comment from kriegaex - Move batch compiler to Java 17, drop Java 11 runtime support #886 (comment). Surely there would be other bigger consumers such as Apache Tomcat.
• Java 17 is fairly new, by Java standards and only a year and half old. Those clients that prefer to go with tried and tested software will not be happy about this.

Important notes

• Compilation targets will be not affected, ECJ will still support compilation targets from Java 20 down to Java 1.8.
• Voting deadline is one week, means 29.03.2023 is the last voting day.

[akurtakov]

Please set a deadline for voting. IMHO 1 week is enough for whoever is interested to cast his/her vote.

[iloveeclipse]

Please set a deadline for voting.

How? I don't see any "deadline" or whatever option in the github UI. Or do you mean "add a note to the poll text about deadline"?

[akurtakov]

Add a note to the poll text. Such functionality is not yet implemented but the request for it is community/community#44890

[iloveeclipse]

Done

[jarthana]

I think it's only fair that we present both sides of the argument. In fact, this should go to the comment 0.

• First and foremost, Java 11 is still an active version that is still being supported by Oracle. Platform moving ahead is a complex case, but there's no such reason to do that in the batch compiler case.
• We should take a moment to think about all the ECJ consumers we will either be leaving behind or upsetting. Case in point, the comment from kriegaex - Move batch compiler to Java 17, drop Java 11 runtime support #886 (comment). Surely there would be other bigger consumers such as Apache Tomcat.

[iloveeclipse]

Thanks Jay, I've updated the voting text to include your comments 1:1.
I believe you should be able to update description too, so feel free to do so.

[iloveeclipse]

OK, closing this one.
Status: 16 votes, 62% "yes", 31% "no", 6% "don't care".