Bug#1006647: libeclipse-jdt-core-java 4.21 breaks Java 8 compatibility for Tomcat

[Per Lundberg]

Package: libeclipse-jdt-core-java
Version: 3.27.0+eclipse4.21-1
Severity: normal

Dear Maintainer,

The 3.27.0+eclipse4.21-1 version of the package has switched to using
the 4.21 version of the upstream package (libeclipse-jdt-core-java).
This is problematic for us and potentially others who are still forced
to use JDK 8, since this version has a strict Java 11 requirement. (This
is also listed in the changelog entry for the package.)

More so, this package is used as-is in Ubuntu (including the upcoming
Ubuntu 22.04 release), which means that the decision to bump the
libeclipse-jdt-core-java to a version which only works on Java 11 and
greater has significant ramifications to the ecosystem at large.

The 4.21 version is not _required_ by Tomcat 9.0.58. It works fine on
4.20 (and perhaps older versions as well, as we also indicate by the
libeclipse-jdt-core-java (>= 3.18.0) dependency line for the
libtomcat9-java package.

I see some ways this could be handled by the Debian project:

* Live with it. People who still are using JDK 8 are on their own anyway
  (Oracle does not support it). Unfortunately, this will cause problems
  for a number of people, who will be forced to find other ways than
  using the vendor-provided Tomcat package if their software cannot run
  on Java 11.

* Downgrade the version in Debian to 4.20. This should make our Tomcat
  work on JDK 8 and 11 alike, and be the "most compatible" approach in
  this case. I think this would be preferable if possible.

I don't know, but I wonder if providing a 4.21-based package in Debian
in this case could be an unintentional mistake? I just downloaded the
Tomcat 9.0.58 tarball from
https://archive.apache.org/dist/tomcat/tomcat-9/v9.0.58/, and it
contains the lib/ecj-4.20.jar file, i.e. containing Eclipse JDT version
4.20. I would _guess_ that this is specifically done to avoid enforcing
a Java 11 dependency on all Tomcat users. Tomcat 9 (and 10.0) still
supports Java 8 in their upstream versions.

I'm not in charge of this decision in any way, but I think it does make
sense if Debian would consider doing the same. Especially given that
Debian is a project which takes backwards compatibility very seriously
and works hard to avoid unnecessary breakage for our end users. (In this
case, some of "our end users" are using Ubuntu. :)

Best regards,
Per

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