I'm trying to debug an Eclipse plugin that developed a bug around the 2019-09 timeframe. Something must have changed in the platform that causes it not to work anymore.
I can run the rcp 2018-12 distro and test it, and I verify that it works. I was able to step through the handler code.
If I run the 2019-12 distro, I can't fully compile the project, as it says "The type javax.inject.Inject cannot be resolved.". When I try to open type javax.inject.Inject in the 2018-12 distro, it finds it in "eclipse/plugins/javax.inject_1.0.0.v20091030.jar" in the distro. When I inspect that "plugins" directory, I find lots of separate plugin jars.
In the 2019-12 distro, it can't find javax.inject.Inject, and when I look in that plugins directory, I only find a single jar, the "org.eclipse.equinox.launcher" jar.
I remember this subject of the single launcher jar, but I don't know if this is a direct cause of this compile error, or what I have to do to move forward.
Update:
In response to the much appreciated answer, here's what I found:
I do find a ~/.p2 directory, and I found the javax.inject plugin in there. When I inspect the "Target Platform" settings, I see very similar information in both the 2018-12 and 2019-12 instance (plugin count varies by a very small number).
I inspected all of the MANIFEST.MF files, and none of them have a single "Import-Package" statement. I understand the advice is to add one, but I'd like to understand why I'm NOT seeing an error in 2018-12.
When I look at the "Plug-in Dependencies" list in the Project Explorer, I see "javax.inject" in the list in 2018-12, but I don't see it in 2019-12.
When I select the MANIFEST.MF file and view it in the form mode and select "Dependency Analysis" and then "Show the plug-in dependency hierarchy", I can then see that "org.eclipse.core.runtime", which is version 3.15... in 2018-12 and version 3.17... in 2019-12 has different dependencies. In particular, in 3.15, one of the dependencies is "javax.inject". In 3.17, that is not one of its dependencies.
So, I can see that a possible solution is definitely to add an "Import-Package" for "javax.inject", but can you explain why it might be that NONE of the MANIFEST.MF files have a single "Import-Package" statement as of yet?
If you are using an Eclipse installed with the Oomph installer the plugins can be in a different location (the .p2 direcory in your home directory I think). The javax.inject plugin should still be present along with all the other Eclipse plugins.
Plugins normally reference javax.inject using Import-Package in the MANIFEST.MF rather than specifying the required plugin use Require-Package so:
Import-Package: javax.inject
There haven't been any significant changes in this area between 2018-12 and 2019-12. The version of javax.inject is still exactly the same.
Check what you have configured as your Target Platform (Preferences > Plug-in Development > Target Platform) - that determines what plug-ins are available.
Update: The reason you now need to add the Import-Package is the change made by Eclipse bug 487676 which removed the 're-export' of the javax.inject dependency from org.eclipse.core.runtime so that you now have to explicitly add it. This is also documented in the Whats New for Eclipse 2019-09 (4.13)
Note that Eclipse 2023-12 (4.30) has moved to using jakarta.inject rather than javax.inject see here