Skip completely inaccessible classpath elements in package caching

Author: HannesWell

org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/JavaProjectElementInfo.java

@@ -13,6 +13,7 @@
  *******************************************************************************/
 package org.eclipse.jdt.internal.core;
 
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 import org.eclipse.core.resources.IContainer;
@@ -26,6 +27,9 @@
 import org.eclipse.jdt.core.IPackageFragmentRoot;
 import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.jdt.core.JavaModelException;
+import org.eclipse.jdt.core.compiler.IProblem;
+import org.eclipse.jdt.internal.compiler.env.AccessRule;
+import org.eclipse.jdt.internal.compiler.env.AccessRuleSet;
 import org.eclipse.jdt.internal.core.DeltaProcessor.RootInfo;
 import org.eclipse.jdt.internal.core.util.HashSetOfArray;
 import org.eclipse.jdt.internal.core.util.HashtableOfArrayToObject;
@@ -234,7 +238,13 @@ ProjectCache getProjectCache(JavaProject project, boolean excludeTestCode) {
 			JavaModelManager  manager = JavaModelManager.getJavaModelManager();
 			for (int i = 0; i < length; i++) {
 				IPackageFragmentRoot root = roots[i];
+				if (reverseMap.get(root) instanceof ClasspathEntry cpEntry && isCompletelyNonAccessible(cpEntry)) {
+					//TODO: Do we have to update the roots entry like below?
+					pkgFragmentsCaches.put(root, new HashSetOfArray());
+					continue;
+				}
 				DeltaProcessor.RootInfo rootInfo = rootInfos.get(root.getPath());
+				//TODO: Check this. Is this a hot loop where we can filter in accessible elements?
 				if (rootInfo == null || rootInfo.project.equals(project)) {
 					// ensure that an identical root is used (see https://bugs.eclipse.org/bugs/show_bug.cgi?id=217059 )
 					roots[i] = root = (IPackageFragmentRoot) manager.getExistingElement(root);
@@ -255,6 +265,22 @@ ProjectCache getProjectCache(JavaProject project, boolean excludeTestCode) {
 		return cache;
 	}
 
+	private static final char[] ALL_ELEMENTS = {'*', '*', '/', '*'};
+
+	private boolean isCompletelyNonAccessible(ClasspathEntry cpEntry) {
+		AccessRuleSet accessRules = cpEntry.getAccessRuleSet();
+		if (accessRules != null) {
+			AccessRule[] rules = accessRules.getAccessRules();
+			if (rules.length == 1) {
+				AccessRule rule = rules[0];
+				if (rule.getProblemId() == IProblem.ForbiddenReference && Arrays.equals(rule.pattern, ALL_ELEMENTS)) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
 	/**
 	 * Returns an array of non-java resources contained in the receiver.
 	 */