Fix findAnnotations() for standalone/fat Multi-Release JARs

NameLookup.findType() with ACCEPT_ANNOTATIONS may fail to resolve
annotation types from standalone/fat Multi-Release JARs such as
junit-platform-console-standalone-1.13.4.jar. This causes JUnit 5
test launches to fail with "Cannot find Testable on project build path".

Add a fallback that retries with ACCEPT_ALL when the strict
ACCEPT_ANNOTATIONS lookup finds nothing. The fallback still enforces
access restrictions (checkRestrictions=true + isNonAccessible check)
and verifies the resolved type is actually an annotation, so the
PDE forbidden-transitive-dependency case remains protected.

The fallback is skipped when the original lookup found the type but
it was access-restricted, to avoid reviving forbidden dependencies.

Fixes: #2959

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: wenytang-ms

org.eclipse.jdt.junit.core/src/org/eclipse/jdt/internal/junit/util/CoreTestSearchEngine.java

@@ -356,6 +356,7 @@ public static void findSuiteMethods(IJavaElement element, Set<IType> result, IPr
 	private static IType findAnnotations(IJavaProject project, String... fullyQualifiedNames) throws JavaModelException {
 		if (project instanceof JavaProject p) {
 			NameLookup lookup= p.newNameLookup(DefaultWorkingCopyOwner.PRIMARY);
+			boolean foundButRestricted= false;
 			for (String fullyQualifiedName : fullyQualifiedNames) {
 				NameLookup.Answer answer = lookup.findType(
 						fullyQualifiedName,
@@ -365,8 +366,34 @@ private static IType findAnnotations(IJavaProject project, String... fullyQualif
 						true /* wait for indexer */,
 						true /* check restrictions */,
 						null);
-				if (answer != null && !answer.isNonAccessible()) {
-					return answer.type;
+				if (answer != null) {
+					if (!answer.isNonAccessible()) {
+						return answer.type;
+					}
+					foundButRestricted= true;
+				}
+			}
+			// Fallback for standalone/fat JARs (e.g. junit-platform-console-standalone)
+			// where NameLookup with ACCEPT_ANNOTATIONS may fail to resolve annotation
+			// types from Multi-Release JARs. Retry with ACCEPT_ALL but still enforce
+			// access restrictions and verify the resolved type is actually an annotation.
+			// Only fall back when the type was genuinely not found, not when it was found
+			// but restricted — to avoid reviving a forbidden transitive dependency.
+			// See: https://github.com/eclipse-jdt/eclipse.jdt.ui/issues/2959
+			if (!foundButRestricted) {
+				for (String fullyQualifiedName : fullyQualifiedNames) {
+					NameLookup.Answer answer = lookup.findType(
+							fullyQualifiedName,
+							false /* no partial matches */,
+							NameLookup.ACCEPT_ALL,
+							false /* no secondary types */,
+							true /* wait for indexer */,
+							true /* check restrictions */,
+							null);
+					if (answer != null && !answer.isNonAccessible()
+							&& answer.type != null && answer.type.isAnnotation()) {
+						return answer.type;
+					}
 				}
 			}
 		}