Fix package path computation in ClasspathScanner

Fix `getRootUrisForPackage()` in class `ClasspathScanner` by looking for two
"wordings" of a package name.

For example, package `foo.bar` is expanded to `foo/bar` and `foo/bar/`.
The latter allows find package `foo.bar` in a module called `foo.bar`,
and not `foo`.
This commit also ensures, that there's no regression (compared to #2531)
by launching test runs using the standalone artifact with `--select-package`
and `--scan-class-path`.

Fixes #2500
Fixes #2600
Fixes #2612

documentation/src/docs/asciidoc/release-notes/release-notes-5.8.0-M2.adoc

@@ -15,7 +15,9 @@ on GitHub.
 
 ==== Bug Fixes
 
-* ❓
+* Method `getRootUrisForPackage()` in class `ClasspathScanner` now returns a
+  valid list of class names when the package name is equal to the name of a
+  module on the module path and when running on Java 8.
 
 ==== Deprecations and Breaking Changes
 

junit-platform-commons/src/main/java/org/junit/platform/commons/util/ClasspathScanner.java

@@ -25,7 +25,9 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Enumeration;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -50,6 +52,8 @@ class ClasspathScanner {
 	private static final Logger logger = LoggerFactory.getLogger(ClasspathScanner.class);
 
 	private static final char CLASSPATH_RESOURCE_PATH_SEPARATOR = '/';
+	private static final String CLASSPATH_RESOURCE_PATH_SEPARATOR_STRING = String.valueOf(
+		CLASSPATH_RESOURCE_PATH_SEPARATOR);
 	private static final char PACKAGE_SEPARATOR_CHAR = '.';
 	private static final String PACKAGE_SEPARATOR_STRING = String.valueOf(PACKAGE_SEPARATOR_CHAR);
 
@@ -76,7 +80,8 @@ List<Class<?>> scanForClassesInPackage(String basePackageName, ClassFilter class
 		Preconditions.notNull(classFilter, "classFilter must not be null");
 		basePackageName = basePackageName.trim();
 
-		return findClassesForUris(getRootUrisForPackage(basePackageName), basePackageName, classFilter);
+		return findClassesForUris(getRootUrisForPackageNameOnClassPathAndModulePath(basePackageName), basePackageName,
+			classFilter);
 	}
 
 	List<Class<?>> scanForClassesInClasspathRoot(URI root, ClassFilter classFilter) {
@@ -212,12 +217,29 @@ private ClassLoader getClassLoader() {
 		return this.classLoaderSupplier.get();
 	}
 
+	private List<URI> getRootUrisForPackageNameOnClassPathAndModulePath(String basePackageName) {
+		Set<URI> uriSet = new LinkedHashSet<>(getRootUrisForPackage(basePackageName));
+		if (!basePackageName.isEmpty() && !basePackageName.endsWith(PACKAGE_SEPARATOR_STRING)) {
+			getRootUrisForPackage(basePackageName + PACKAGE_SEPARATOR_STRING).stream() //
+					.map(ClasspathScanner::removeTrailingClasspathResourcePathSeparator) //
+					.forEach(uriSet::add);
+		}
+		return new ArrayList<>(uriSet);
+	}
+
+	private static URI removeTrailingClasspathResourcePathSeparator(URI uri) {
+		String string = uri.toString();
+		if (string.endsWith(CLASSPATH_RESOURCE_PATH_SEPARATOR_STRING)) {
+			return URI.create(string.substring(0, string.length() - 1));
+		}
+		return uri;
+	}
+
 	private static String packagePath(String packageName) {
 		if (packageName.isEmpty()) {
 			return "";
 		}
-		String path = packageName.replace(PACKAGE_SEPARATOR_CHAR, CLASSPATH_RESOURCE_PATH_SEPARATOR);
-		return path + CLASSPATH_RESOURCE_PATH_SEPARATOR;
+		return packageName.replace(PACKAGE_SEPARATOR_CHAR, CLASSPATH_RESOURCE_PATH_SEPARATOR);
 	}
 
 	private List<URI> getRootUrisForPackage(String basePackageName) {

platform-tooling-support-tests/src/test/java/platform/tooling/support/tests/StandaloneTests.java

@@ -30,6 +30,7 @@
 import org.junit.jupiter.api.Order;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestMethodOrder;
+import org.opentest4j.TestAbortedException;
 
 import platform.tooling.support.Helper;
 import platform.tooling.support.MavenRepo;
@@ -121,6 +122,73 @@ void test() throws IOException {
 
 	@Test
 	@Order(3)
+	void testOnJava8() throws IOException {
+		var result = Request.builder() //
+				.setTool(new Java()) //
+				.setJavaHome(Helper.getJavaHome("8").orElseThrow(TestAbortedException::new)) //
+				.setProject("standalone") //
+				.addArguments("--show-version") //
+				.addArguments("-enableassertions") //
+				.addArguments("-Djava.util.logging.config.file=logging.properties") //
+				.addArguments("-jar", MavenRepo.jar("junit-platform-console-standalone")) //
+				.addArguments("--scan-class-path") //
+				.addArguments("--disable-banner") //
+				.addArguments("--include-classname", "standalone.*") //
+				.addArguments("--classpath", "bin").build() //
+				.run(false);
+
+		assertEquals(1, result.getExitCode(), String.join("\n", result.getOutputLines("out")));
+
+		var workspace = Request.WORKSPACE.resolve("standalone");
+		var expectedOutLines = Files.readAllLines(workspace.resolve("expected-out.txt"));
+		var expectedErrLines = Files.readAllLines(workspace.resolve("expected-err.txt"));
+		assertLinesMatch(expectedOutLines, result.getOutputLines("out"));
+		assertLinesMatch(expectedErrLines, result.getOutputLines("err"));
+
+		var jupiterVersion = Helper.version("junit-jupiter-engine");
+		var vintageVersion = Helper.version("junit-vintage-engine");
+		assertTrue(result.getOutput("err").contains("junit-jupiter"
+				+ " (group ID: org.junit.jupiter, artifact ID: junit-jupiter-engine, version: " + jupiterVersion));
+		assertTrue(result.getOutput("err").contains("junit-vintage"
+				+ " (group ID: org.junit.vintage, artifact ID: junit-vintage-engine, version: " + vintageVersion));
+	}
+
+	@Test
+	@Order(3)
+	// https://github.com/junit-team/junit5/issues/2600
+	void testOnJava8SelectPackage() throws IOException {
+		var result = Request.builder() //
+				.setTool(new Java()) //
+				.setJavaHome(Helper.getJavaHome("8").orElseThrow(TestAbortedException::new)) //
+				.setProject("standalone") //
+				.addArguments("--show-version") //
+				.addArguments("-enableassertions") //
+				.addArguments("-Djava.util.logging.config.file=logging.properties") //
+				.addArguments("-jar", MavenRepo.jar("junit-platform-console-standalone")) //
+				.addArguments("--select-package", "standalone") //
+				.addArguments("--disable-banner") //
+				.addArguments("--include-classname", "standalone.*") //
+				.addArguments("--classpath", "bin").build() //
+				.run(false);
+
+		assertEquals(1, result.getExitCode(), String.join("\n", result.getOutputLines("out")));
+
+		var workspace = Request.WORKSPACE.resolve("standalone");
+		var expectedOutLines = Files.readAllLines(workspace.resolve("expected-out.txt"));
+		var expectedErrLines = Files.readAllLines(workspace.resolve("expected-err.txt"));
+		assertLinesMatch(expectedOutLines, result.getOutputLines("out"));
+		assertLinesMatch(expectedErrLines, result.getOutputLines("err"));
+
+		var jupiterVersion = Helper.version("junit-jupiter-engine");
+		var vintageVersion = Helper.version("junit-vintage-engine");
+		assertTrue(result.getOutput("err").contains("junit-jupiter"
+				+ " (group ID: org.junit.jupiter, artifact ID: junit-jupiter-engine, version: " + jupiterVersion));
+		assertTrue(result.getOutput("err").contains("junit-vintage"
+				+ " (group ID: org.junit.vintage, artifact ID: junit-vintage-engine, version: " + vintageVersion));
+	}
+
+	@Test
+	@Order(5)
 	@Disabled("https://github.com/junit-team/junit5/issues/1724")
 	void testWithJarredTestClasses() {
 		var jar = MavenRepo.jar("junit-platform-console-standalone");