Bug 94367 cannot clear compiler compliance setting at the project level
i200505092010 Cannot disable the Java compiler project-specific preferences for some projects. Steps to reproduce: 1 - check out from CVS a Java project that has project-specific Java compiler settings enabled (example: org.eclipse.core.runtime). 2 - open the properties dialog for the project, select the Java compiler node, disable project-specific Java compiler preferences. 3 - Commit the changes by pressing "Ok" and reopen the properties dialog. It looks like the settings were not saved (project-specific settings are still enabled).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/OptionsConfigurationBlock.java
public static final class Key {
		
		private String fQualifier;
		private String fKey;
		
		public Key(String qualifier, String key) {
			fQualifier= qualifier;
			fKey= key;
		}
		
		public String getName() {
			return fKey;
		}
		
		private IEclipsePreferences getNode(IScopeContext context, IWorkingCopyManager manager) {
			IEclipsePreferences node= context.getNode(fQualifier);
			if (manager != null) {
				return manager.getWorkingCopy(node);
			}
			return node;
		}
		
		public String getStoredValue(IScopeContext context, IWorkingCopyManager manager) {
			return getNode(context, manager).get(fKey, null);
		}