Fail on classpath resource names that are blank after removing leading /

Fixes #4752.

Author: marcphilipp

documentation/src/docs/asciidoc/release-notes/release-notes-5.13.4.adoc

@@ -26,7 +26,8 @@ repository on GitHub.
 [[release-notes-5.13.4-junit-platform-bug-fixes]]
 ==== Bug Fixes
 
-* ❓
+* `ClasspathResourceSelector` no longer allows to be constructed with a resource name that
+  is blank after removing the leading slash.
 
 [[release-notes-5.13.4-junit-platform-deprecations-and-breaking-changes]]
 ==== Deprecations and Breaking Changes

junit-platform-engine/src/main/java/org/junit/platform/engine/discovery/ClasspathResourceSelector.java

@@ -25,6 +25,7 @@
 import org.junit.platform.commons.PreconditionViolationException;
 import org.junit.platform.commons.function.Try;
 import org.junit.platform.commons.support.Resource;
+import org.junit.platform.commons.util.Preconditions;
 import org.junit.platform.commons.util.ReflectionUtils;
 import org.junit.platform.commons.util.StringUtils;
 import org.junit.platform.commons.util.ToStringBuilder;
@@ -64,6 +65,8 @@ public final class ClasspathResourceSelector implements DiscoverySelector {
 	ClasspathResourceSelector(String classpathResourceName, @Nullable FilePosition position) {
 		boolean startsWithSlash = classpathResourceName.startsWith("/");
 		this.classpathResourceName = (startsWithSlash ? classpathResourceName.substring(1) : classpathResourceName);
+		Preconditions.notBlank(this.classpathResourceName,
+			"classpath resource name must not be blank after removing leading slash");
 		this.position = position;
 	}
 

platform-tests/src/test/java/org/junit/platform/engine/discovery/DiscoverySelectorsTests.java

@@ -299,8 +299,11 @@ void parseDirectorySelectorWithAbsolutePath() {
 		void selectClasspathResourcesPreconditions() {
 			assertViolatesPrecondition(() -> selectClasspathResource((String) null));
 			assertViolatesPrecondition(() -> selectClasspathResource(""));
+			assertViolatesPrecondition(() -> selectClasspathResource("/"));
 			assertViolatesPrecondition(() -> selectClasspathResource("    "));
+			assertViolatesPrecondition(() -> selectClasspathResource("/   "));
 			assertViolatesPrecondition(() -> selectClasspathResource("\t"));
+			assertViolatesPrecondition(() -> selectClasspathResource("/\t"));
 			assertViolatesPrecondition(() -> selectClasspathResource((Set<Resource>) null));
 			assertViolatesPrecondition(() -> selectClasspathResource(Collections.emptySet()));
 			assertViolatesPrecondition(() -> selectClasspathResource(Collections.singleton(null)));