[cross-project-issues-dev] P2 and feature dependencies

["Mik Kersten" <mik@xxxxxxxxxxx>]

Following up the brief feature discussion on the call, here's the pointer to
David William's bug:

  231453: P2 doesn't install all features, compared to UpdateManager
  https://bugs.eclipse.org/bugs/show_bug.cgi?id=231453

Unless I've missed something this is what it boils down to:

* Update Manger would scan a feature's plug-in dependencies before allowing
that feature to be installed.  As such, a user could not install plug-ins
from a feature that would not load due to missing dependencies.

* In P2 this no longer happens when the user is selecting features, meaning
that if you rely on plug-in dependencies alone users can end up with partial
updates.  In earlier RCs we saw this happen with people trying to install
Mylyn 3.0 and ending up with only some of the required features installed.
This is because a while back we purposely removed all feature dependencies
to avoid a bug in the Update Manager (see bug 132450).  

* Specifying dependencies at the feature level appears to address the
problem.  For each feature we now specify all the features that it requires
in addition to specifying the plug-in dependencies.  We only made the change
mid last week and are still testing.  

One thing we haven't had a chance to test yet is the automatic updates.
There were serious problems with them in Eclipse 3.2, so it's worth checking
if dependencies install correctly.  We'll set up a test update site for
this, but if anyone has any experience testing automatic updates work with
their project and P2 please post.

Mik

P.S. Thanks David for identifying this!  All of your work and input on
orbit, build and install has been a big help.

--
Mik Kersten
President & CTO, http://tasktop.com 
Project Lead, http://eclipse.org/mylyn