Eclipse can be a little wilful at times. There are a bunch of "magic operations" that you might need to do in various occasions, to resolve some inconsistencies in the Eclipse workspace and other things. Find them below, in no particular order.
- Project > Clean... >
- Click "clean all projects"
- Click "OK"
Reset target platform
- Type Ctrl+Shift+R to get up the resource opener dialog
- Select the option "target-platform.target - net.bioclipse.target.platform"
- Click "open"
- Wait for the "resolving target" work in the background to finish.
- Make sure your Eclipse window is large enough that you see the "Set as target platform" link in the top right.
- Click that link.
- Wait for the target reset to finish.
- Save the file (Ctrl + S)
- Select any project in the file explorer view to the left.
- Right click the project
- Sleect "PDE Tools"
- Click "Update classpath"
- Click "Select all"
- Click "Finish"
Add required plugins
After you have run your project from a *.product file sometime, there will be a saved run configuration under "Run > Run configurations ...".
- Open your existing run config: Run > Run configurations
- Click the "Plug-ins" tab
- Click "Validate Plug-ins"
- If there are any plugins showing up in the resulting dialog, continue.
- Click "Ok"
- Click "Add Required Plug-ins"
- That's it.