Disable plugin loading on illegal/ not set plugin dir

src/main/java/org/cryptomator/integrations/common/ClassLoaderFactory.java

@@ -18,7 +18,6 @@
 class ClassLoaderFactory {
 
 	private static final Logger LOG = LoggerFactory.getLogger(ClassLoaderFactory.class);
-	private static final String USER_HOME = System.getProperty("user.home");
 	private static final String PLUGIN_DIR_KEY = "cryptomator.pluginDir";
 	private static final String JAR_SUFFIX = ".jar";
 
@@ -30,21 +29,27 @@ class ClassLoaderFactory {
 	 */
 	@Contract(value = "-> new", pure = true)
 	public static URLClassLoader forPluginDir() {
-		String val = System.getProperty(PLUGIN_DIR_KEY, "");
-		final Path p;
-		if (val.startsWith("~/")) {
-			p = Path.of(USER_HOME).resolve(val.substring(2));
-		} else {
-			p = Path.of(val);
+		String val = System.getProperty(PLUGIN_DIR_KEY);
+		if (val == null) {
+			return URLClassLoader.newInstance(new URL[0]);
+		}
+
+		try {
+			if (val.isBlank()) {
+				throw new IllegalArgumentException("Plugin dir path is blank");
+			}
+			return forPluginDirWithPath(Path.of(val)); //Path.of() might throw InvalidPathException
+		} catch (IllegalArgumentException e) {
+			LOG.debug("{} contains illegal value. Skipping plugin directory.", PLUGIN_DIR_KEY, e);
+			return URLClassLoader.newInstance(new URL[0]);
 		}
-		return forPluginDirWithPath(p);
 	}
 
 	@VisibleForTesting
 	@Contract(value = "_ -> new", pure = true)
 	static URLClassLoader forPluginDirWithPath(Path path) throws UncheckedIOException {
 		var jars = findJars(path);
-		if (LOG.isDebugEnabled()) {
+		if (LOG.isDebugEnabled() && jars.length != 0) {
 			String jarList = Arrays.stream(jars).map(URL::getPath).collect(Collectors.joining(", "));
 			LOG.debug("Found jars in cryptomator.pluginDir: {}", jarList);
 		}
@@ -56,7 +61,7 @@ static URL[] findJars(Path path) {
 		try (var stream = Files.walk(path)) {
 			return stream.filter(ClassLoaderFactory::isJarFile).map(ClassLoaderFactory::toUrl).toArray(URL[]::new);
 		} catch (IOException | UncheckedIOException e) {
-			// unable to locate any jars // TODO: log a warning?
+			LOG.debug("Failed to read plugin dir {}", path, e);
 			return new URL[0];
 		}
 	}

src/test/java/org/cryptomator/integrations/common/ClassLoaderFactoryTest.java

@@ -1,11 +1,16 @@
 package org.cryptomator.integrations.common;
 
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+import org.mockito.MockedStatic;
 import org.mockito.Mockito;
 
 import java.io.ByteArrayInputStream;
@@ -17,6 +22,9 @@
 import java.util.Arrays;
 import java.util.Comparator;
 
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.never;
+
 public class ClassLoaderFactoryTest {
 
 	@Nested
@@ -91,21 +99,49 @@ public void testReadPluginDirFromSysProp() {
 		}
 	}
 
-	@Test
-	@DisplayName("read path from cryptomator.pluginDir and replace ~/ with user.home")
-	public void testReadPluginDirFromSysPropAndReplaceHome() {
-		var ucl = Mockito.mock(URLClassLoader.class, "ucl");
-		var relPath = "~/there/will/be/plugins";
-		var absPath = Path.of(System.getProperty("user.home")).resolve("there/will/be/plugins");
-		try (var mockedClass = Mockito.mockStatic(ClassLoaderFactory.class)) {
+	@Nested
+	@DisplayName("when the system property contains invalid values")
+	public class InvalidSystemProperty {
+
+		MockedStatic<ClassLoaderFactory> mockedClass;
+
+		@BeforeEach
+		public void beforeEach() {
+			mockedClass = Mockito.mockStatic(ClassLoaderFactory.class);
 			mockedClass.when(() -> ClassLoaderFactory.forPluginDir()).thenCallRealMethod();
-			mockedClass.when(() -> ClassLoaderFactory.forPluginDirWithPath(absPath)).thenReturn(ucl);
+			mockedClass.when(() -> ClassLoaderFactory.forPluginDirWithPath(any())).thenReturn(null);
+		}
 
-			System.setProperty("cryptomator.pluginDir", relPath);
+		@AfterEach
+		public void afterEach() {
+			mockedClass.close();
+		}
+
+
+		@Test
+		@DisplayName("Undefined cryptomator.pluginDir returns empty URLClassLoader")
+		public void testUndefinedSysProp() {
+			System.clearProperty("cryptomator.pluginDir");
 			var result = ClassLoaderFactory.forPluginDir();
 
-			Assertions.assertSame(ucl, result);
+			mockedClass.verify(() -> ClassLoaderFactory.forPluginDirWithPath(any()), never());
+			Assertions.assertNotNull(result);
+			Assertions.assertEquals(0, result.getURLs().length);
 		}
+
+		@ParameterizedTest
+		@DisplayName("Property cryptomator.pluginDir filled with blanks returns empty URLClassLoader")
+		@EmptySource
+		@ValueSource(strings = {"\t\t", "  "})
+		public void testBlankSysProp(String propValue) {
+			System.setProperty("cryptomator.pluginDir", propValue);
+			var result = ClassLoaderFactory.forPluginDir();
+
+			mockedClass.verify(() -> ClassLoaderFactory.forPluginDirWithPath(any()), never());
+			Assertions.assertNotNull(result);
+			Assertions.assertEquals(0, result.getURLs().length);
+		}
+
 	}
 
 	@Test