Preventing source plug-ins from added as depencies in the MANIFEST.MF

[vogella]

In my plugin and RCP training sessions participants frequently add "sources" as dependencies in the MANIFEST and therefore their products do not start anymore as they are not part of their product / features.

Can we avoid this? Maybe we can just filter sources from the list of plugins which can be added to the MANIFEST.MF? cc @HannesWell who recently update the source generation in multiple places.

[HannesWell]

At least Source-Bundles build by Tycho have a Eclipse-SourceBundle header in their MANIFEST and IIRC PDE requires that in order to be able to locate sources of bundles. This would be a reliable test that does not rely on naming conventions.
But I'm not sure if this also applies to the sources of all Maven-artifacts (it would be great, but I don't think this is the case for all that have a OSGi-compliant MANIFEST). However @laeubi recently created a Tycho-Plugin to simplify that: https://github.com/eclipse/tycho/blob/master/RELEASE_NOTES.md#automatic-generation-of-pde-source-bundles-for-pom-first-bundles.

And once we have a reliable test if a bundle is a source-bundle it should be fairly easy to filter out source bundles in the Add Required Plug-ins dialog. Additionally PDE could issue an error with explanatory message (whose severity can be configured) if it detects a required source-bundle in existing manifests.

Nevertheless in general it is recommended to use Import-Package instead of Require-Bundle (which is deprecated according to the OSGi-spec). For example the transition to OSGi-Bundles from Maven-Central would be simpler if Eclipse would use only Import-Package. The Plug-ins embedding those source could then be removed immediately. But before we evangelize this more PDE should improve its support for that (but that's another discussion).

[laeubi]

Additionally PDE could issue an error with explanatory message (whose severity can be configured) if it detects a required source-bundle in existing manifests.

Source bundles are regular bundles so it is not an error.

And once we have a reliable test if a bundle is a source-bundle it should be fairly easy to filter out source bundles in the Add Required Plug-ins dialog

We better error the on using require-bundle at all ;-)

[HannesWell]

Additionally PDE could issue an error with explanatory message (whose severity can be configured) if it detects a required source-bundle in existing manifests.

Source bundles are regular bundles so it is not an error.

That's right. Then it should be a warning, although people are too used to warnings and therefore often oversee them respectively have too many in the workspace that new ones are not recognized. But making them used to errors is probably also not a good idea.

And once we have a reliable test if a bundle is a source-bundle it should be fairly easy to filter out source bundles in the Add Required Plug-ins dialog

We better error the on using require-bundle at all ;-)

I do not disagree but its another discussion. :)

[laeubi]

@HannesWell just for completeness PDE requires the Eclipse-SourceBundle header and the maven target integration adds missing headers if required.
If you include maven dependencies directly you can't use them as source bundles (unless they already have headers), but if you produce maven-first bundles you can generate a source bundle that contains the headers.

Beside that, PDE won't strictly require the header and actually the target-platfrom has a method to test if an arbitrary bundle is a source bundle but it seems not be implemented down further in PDE itself to use that method.

[vogella]

But I'm not sure if this also applies to the sources of all Maven-artifact

Some support is better than no support, so I will create a issue and plan to look into it. Thanks Hannes.

[laeubi]

Can we avoid this? Maybe we can just filter sources from the list of plugins which can be added to the MANIFEST.MF?

The question is: Why they do that? This is not an error and maybe even desired, who knows?

[vogella]

@vogella this is an open discussion so I think you have to scope with that

:-) you are funny.

[laeubi]

OSS is fun isn't it :-) If I'm doing what other telling me it is most often payed work and not OSS and not always fun ...

[vogella]

OSS is fun isn't it :-) If I'm doing what other telling me it is most often payed work and not OSS and not always fun ...

Indeed. I'm also in the luxary position of getting almost never paid for OS work, just image how stressful it would be to work on OS and get money from it. :-)

[laeubi]

Indeed. I'm also in the luxary position of getting almost never paid for OS work

You probably could ask your customer of that training sessions if the want to pay you to implement (including tests, documentation PRs discussions) this feature... or if that increases the learning curve not adding source bundles at the first place :-D

[vogella]

Every new group of people makes this error. So if I implement this it is mainly for me, saving the time to explain new plugin developers that adding source bundles as dependencies is wrong. It is one of these things you (hopefully) do only wrong once.

[vogella]

Nevertheless in general it is recommended to use Import-Package instead of Require-Bundle

IMHO this depends. If a plug-in requires tons of packages, e.g. like SWT it is so much easier to use plug-in dependencies compared to import packages as you would have to add a lot of package to use SWT which makes it time consuming and hard to read.
Also we have no alternative SWT implementations floating around using import package for SWT is not adding value.

[laeubi]

You don't need to add all packages anyways and PDE suggest you to import them as you have missing imports.

[vogella]

But lets not start a import package vs. required bundles here. This is about source bundles. :-)

[vogella]

#52