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

[John Arthorne <John_Arthorne@xxxxxxxxxx>]

> * 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.

To clarify, Update Manager required
a *feature* to be present containing the required plug-ins. This meant
the user would have to select additional features until the set of selected
features contained the required plug-ins. With p2, if you require a plug-in,
it will be satisfied if just that plug-in is present and not require entire
features to be installed. Thus both UM and p2 require dependencies to be
satisfied before proceeding with the install. The difference is that p2
does this dependency resolution at plug-in granularity as opposed to feature
granularity.

John

"Mik Kersten" <mik@xxxxxxxxxxx>
Sent by: cross-project-issues-dev-bounces@xxxxxxxxxxx

06/09/2008 11:48 AM

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

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


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