With 2.0, for the first time the default Jenkins distribution does not install bundled plugins. This includes all plugins detached from core, i.e. those that used to be a core feature, and are an implied dependency of plugins depending on an older version of core that still bundled them.

Unfortunately, the Plugin Manager cannot handle this:

Steps to reproduce

1. Install Jenkins 2.0 without installing any plugins
2. Go to the plugin manager and install Flexible Publish plugin

Expected result

Flexible Publish plugin and Matrix Project plugin, possibly others, get installed.

Actual result

Token Macro Plugin, Run Condition Plugin, Flexible Publish Plugin get installed. No Matrix Project Plugin

Failed to load org.jenkins_ci.plugins.flexible_publish.FlexiblePublisher$FlexiblePublisherDescriptor
java.lang.NoClassDefFoundError: hudson/matrix/MatrixAggregatable

Notes

Similarly, installed but disabled dependencies need to be re-enabled when a plugin requiring them gets installed. This is however not a regression in 2.0.