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

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

@@ -26,7 +26,10 @@ 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.
+* `PackageSource.from(String)` now allows to be constructed with an empty string to
+  indicate the default package.
 
 [[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;
 	}
 

junit-platform-engine/src/main/java/org/junit/platform/engine/support/descriptor/PackageSource.java

@@ -60,7 +60,10 @@ private PackageSource(Package javaPackage) {
 	}
 
 	private PackageSource(String packageName) {
-		this.packageName = Preconditions.notBlank(packageName, "package name must not be null or blank");
+		Preconditions.notNull(packageName, "package name must not be null");
+		Preconditions.condition(packageName.isEmpty() || !packageName.isBlank(),
+			"package name must not contain only whitespace");
+		this.packageName = packageName;
 	}
 
 	/**

junit-platform-launcher/src/main/java/org/junit/platform/launcher/core/DiscoveryIssueCollector.java

@@ -10,6 +10,7 @@
 
 package org.junit.platform.launcher.core;
 
+import static org.junit.platform.commons.util.UnrecoverableExceptions.rethrowIfUnrecoverable;
 import static org.junit.platform.engine.SelectorResolutionResult.Status.FAILED;
 import static org.junit.platform.engine.SelectorResolutionResult.Status.UNRESOLVED;
 
@@ -78,7 +79,7 @@ else if (result.getStatus() == UNRESOLVED && selector instanceof UniqueIdSelecto
 		}
 	}
 
-	static @Nullable TestSource toSource(DiscoverySelector selector) {
+	private static @Nullable TestSource toSource(DiscoverySelector selector) {
 		if (selector instanceof ClassSelector classSelector) {
 			return ClassSource.from(classSelector.getClassName());
 		}
@@ -96,17 +97,26 @@ else if (result.getStatus() == UNRESOLVED && selector instanceof UniqueIdSelecto
 		if (selector instanceof PackageSelector packageSelector) {
 			return PackageSource.from(packageSelector.getPackageName());
 		}
-		if (selector instanceof FileSelector fileSelector) {
-			return fileSelector.getPosition() //
-					.map(DiscoveryIssueCollector::convert) //
-					.map(position -> FileSource.from(fileSelector.getFile(), position)) //
-					.orElseGet(() -> FileSource.from(fileSelector.getFile()));
-		}
-		if (selector instanceof DirectorySelector directorySelector) {
-			return DirectorySource.from(directorySelector.getDirectory());
+		try {
+			// Both FileSource and DirectorySource call File.getCanonicalFile() to normalize the reported file which
+			// can throw an exception for certain file names on certain file systems. UriSource.from(...) is affected
+			// as well because it may return a FileSource or DirectorySource
+			if (selector instanceof FileSelector fileSelector) {
+				return fileSelector.getPosition() //
+						.map(DiscoveryIssueCollector::convert) //
+						.map(position -> FileSource.from(fileSelector.getFile(), position)) //
+						.orElseGet(() -> FileSource.from(fileSelector.getFile()));
+			}
+			if (selector instanceof DirectorySelector directorySelector) {
+				return DirectorySource.from(directorySelector.getDirectory());
+			}
+			if (selector instanceof UriSelector uriSelector) {
+				return UriSource.from(uriSelector.getUri());
+			}
 		}
-		if (selector instanceof UriSelector uriSelector) {
-			return UriSource.from(uriSelector.getUri());
+		catch (Exception ex) {
+			rethrowIfUnrecoverable(ex);
+			logger.warn(ex, () -> "Failed to convert DiscoverySelector [%s] into TestSource".formatted(selector));
 		}
 		return null;
 	}

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)));

platform-tests/src/test/java/org/junit/platform/engine/support/descriptor/PackageSourceTests.java

@@ -18,6 +18,8 @@
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.junit.platform.commons.PreconditionViolationException;
 
 /**
@@ -49,9 +51,11 @@ void packageSourceFromNullPackageReference() {
 		assertThrows(PreconditionViolationException.class, () -> PackageSource.from((Package) null));
 	}
 
-	@Test
-	void packageSourceFromPackageName() {
-		var testPackage = getClass().getPackage().getName();
+	@ParameterizedTest
+	@ValueSource(classes = PackageSourceTests.class)
+	@ValueSource(strings = "DefaultPackageTestCase")
+	void packageSourceFromPackageName(Class<?> testClass) {
+		var testPackage = testClass.getPackage().getName();
 		var source = PackageSource.from(testPackage);
 
 		assertThat(source.getPackageName()).isEqualTo(testPackage);

platform-tests/src/test/java/org/junit/platform/launcher/core/DiscoveryIssueCollectorTests.java

@@ -69,6 +69,7 @@ public static Stream<Pair> pairs() {
 			new Pair(selectClasspathResource("someResource", FilePosition.from(42, 23)),
 				ClasspathResourceSource.from("someResource",
 					org.junit.platform.engine.support.descriptor.FilePosition.from(42, 23))), //
+			new Pair(selectPackage(""), PackageSource.from("")), //
 			new Pair(selectPackage("some.package"), PackageSource.from("some.package")), //
 			new Pair(selectFile("someFile"), FileSource.from(new File("someFile"))), //
 			new Pair(selectFile("someFile", FilePosition.from(42)),