### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.core
Index: model/org/eclipse/jdt/core/JavaCore.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/core/JavaCore.java,v
retrieving revision 1.659
diff -u -r1.659 JavaCore.java
--- model/org/eclipse/jdt/core/JavaCore.java	16 Jan 2011 22:43:21 -0000	1.659
+++ model/org/eclipse/jdt/core/JavaCore.java	15 Apr 2011 07:33:28 -0000
@@ -3530,6 +3530,8 @@
 
 			// initialize all containers and variables
 			JavaModelManager manager = JavaModelManager.getJavaModelManager();
+			ExternalFoldersManager externalFoldersManager = JavaModelManager.getExternalManager();
+			externalFoldersManager.createExternalFoldersProject(monitor);
 			SubProgressMonitor subMonitor = null;
 			try {
 				if (monitor != null) {
@@ -3565,7 +3567,6 @@
 			// and recreate links for external folders if needed
 			if (monitor != null)
 				monitor.subTask(Messages.javamodel_resetting_source_attachment_properties);
-			ExternalFoldersManager externalFoldersManager = JavaModelManager.getExternalManager();
 			final IJavaProject[] projects = manager.getJavaModel().getJavaProjects();
 			HashSet visitedPaths = new HashSet();
 			for (int i = 0, length = projects.length; i < length; i++) {
@@ -3581,22 +3582,32 @@
 					boolean needExternalFolderCreation = false;
 					for (int j = 0, length2 = classpath.length; j < length2; j++) {
 						IClasspathEntry entry = classpath[j];
-						if (entry.getSourceAttachmentPath() != null) {
+						IPath sourceAttachmentPath = null;
+						if ( (sourceAttachmentPath = entry.getSourceAttachmentPath()) != null) {
 							IPath entryPath = entry.getPath();
 							if (visitedPaths.add(entryPath)) {
 								Util.setSourceAttachmentProperty(entryPath, null);
 							}
+							if (ExternalFoldersManager.isExternalFolderPath(sourceAttachmentPath)
+									&& (externalFoldersManager.isPendingFolder(sourceAttachmentPath) || 
+											externalFoldersManager.getFolder(sourceAttachmentPath) == null)) {
+								needExternalFolderCreation = true;
+							}
 						}
 						// else source might have been attached by IPackageFragmentRoot#attachSource(...), we keep it
 						if (!needExternalFolderCreation && entry.getEntryKind() == IClasspathEntry.CPE_LIBRARY) {
 							IPath entryPath = entry.getPath();
-							if (ExternalFoldersManager.isExternalFolderPath(entryPath) && externalFoldersManager.getFolder(entryPath) == null) {
+							if (ExternalFoldersManager.isExternalFolderPath(entryPath)
+									&& (externalFoldersManager.isPendingFolder(entryPath) || 
+											externalFoldersManager.getFolder(entryPath) == null)) {
 								needExternalFolderCreation = true;
 							}
 						}
 					}
+					// https://bugs.eclipse.org/bugs/show_bug.cgi?id=337415
+					// Request for creation of external folder's link instead of relying on delta processing. 
 					if (needExternalFolderCreation)
-						manager.deltaState.addExternalFolderChange(javaProject, null/*act as if all external folders were new*/);
+						new ExternalFolderChange(javaProject, classpath).updateExternalFoldersIfNecessary(false, monitor);
 				}
 			}
 
Index: model/org/eclipse/jdt/internal/core/ExternalFoldersManager.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/ExternalFoldersManager.java,v
retrieving revision 1.21
diff -u -r1.21 ExternalFoldersManager.java
--- model/org/eclipse/jdt/internal/core/ExternalFoldersManager.java	3 Sep 2010 05:13:44 -0000	1.21
+++ model/org/eclipse/jdt/internal/core/ExternalFoldersManager.java	15 Apr 2011 07:33:28 -0000
@@ -193,7 +193,7 @@
 	public IProject getExternalFoldersProject() {
 		return ResourcesPlugin.getWorkspace().getRoot().getProject(EXTERNAL_PROJECT_NAME);
 	}
-	private IProject createExternalFoldersProject(IProgressMonitor monitor) throws CoreException {
+	public IProject createExternalFoldersProject(IProgressMonitor monitor) throws CoreException {
 		IProject project = getExternalFoldersProject();
 		if (!project.isAccessible()) {
 			if (!project.exists()) {
@@ -258,6 +258,9 @@
 		project.create(desc, IResource.HIDDEN, monitor);
 	}
 
+	public boolean isPendingFolder(IPath externalFolderPath) {
+		return this.pendingFolders != null && this.pendingFolders.contains(externalFolderPath);
+	}
 	public IFolder getFolder(IPath externalFolderPath) {
 		return (IFolder) getFolders().get(externalFolderPath);
 	}