<menuContribution locationURI="popup:org.eclipse.ui.projectConfigure?after=additions"> <command commandId="my.command.addRemoveMyNature" label="Enable my nature" style="push"> <visibleWhen checkEnabled="false"> <with variable="selection"> <count value="1" /> <iterate> <adapt type="org.eclipse.core.resources.IProject"> <and> <not> <test property="org.eclipse.core.resources.projectNature" value="my.Nature"> </test> </not> <not> <test property="org.eclipse.core.resources.projectNature" value="org.eclipse.jdt.core.java.javanature"> </test> </not> </and> </adapt> </iterate> </with> </visibleWhen> </command>