fix: Modified the logic to validate basePath as per the pull request reviews

- replaced String#isBlank with StringUtils#isBlank for Java language compatibility
- introduced InvalidBasePathException to be thrown for blank/null/empty values of basepath
- basePath validations moved to the step of storing server arguments to give forward compatibility with Appium v2
fix: added extra test cases for more precisely testing basepath validations

Author: robinGupta11392

src/main/java/io/appium/java_client/service/local/AppiumDriverLocalService.java

@@ -94,23 +94,10 @@ public static AppiumDriverLocalService buildService(AppiumServiceBuilder builder
     }
 
     public AppiumDriverLocalService withBasePath(String basePath) {
-        this.basePath = sanitizeBasePath(basePath);
+        this.basePath = basePath;
         return this;
     }
 
-    @SneakyThrows private static String sanitizeBasePath(String basePath) {
-        if (null == basePath) {
-            LOG.warn("Base Path cannot be NULL -- ignoring the basepath configuration");
-            return null;
-        }
-        basePath = basePath.trim();
-        if (basePath.isBlank() || basePath.isEmpty()) {
-            LOG.warn("Base Path cannot be Empty or Blank -- ignoring the basepath configuration");
-            return null;
-        }
-        return basePath.endsWith("/") ? basePath : basePath + "/";
-    }
-
     public String getBasePath() {
         return this.basePath;
     }

src/main/java/io/appium/java_client/service/local/AppiumServiceBuilder.java

@@ -16,6 +16,7 @@
 
 package io.appium.java_client.service.local;
 
+import static com.google.common.base.Preconditions.checkNotNull;
 import static org.openqa.selenium.remote.CapabilityType.PLATFORM_NAME;
 
 import com.google.common.collect.ImmutableList;
@@ -217,13 +218,25 @@ public AppiumServiceBuilder withArgument(ServerArgument argument, String value)
             case "-g":
                 withLogFile(new File(value));
                 break;
+            case "--base-path":
+                serverArguments.put(argName,sanitizeBasePath(value));
+                break;
             default:
                 serverArguments.put(argName, value);
                 break;
         }
         return this;
     }
 
+    private static String sanitizeBasePath(String basePath) {
+        basePath = checkNotNull(basePath).trim();
+        if (StringUtils.isBlank(basePath) || basePath.isEmpty()) {
+            throw new InvalidBasePathException(
+                "Given base path is not valid - blank or empty values are not allowed for base path");
+        }
+        return basePath.endsWith("/") ? basePath : basePath + "/";
+    }
+
     /**
      * Adds capabilities.
      *

src/main/java/io/appium/java_client/service/local/InvalidBasePathException.java

@@ -0,0 +1,31 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.appium.java_client.service.local;
+
+
+public class InvalidBasePathException extends RuntimeException {
+
+    private static final long serialVersionUID = 1L;
+
+    public InvalidBasePathException(String message, Throwable t) {
+        super(message, t);
+    }
+
+    public InvalidBasePathException(String message) {
+        super(message);
+    }
+}

src/test/java/io/appium/java_client/service/local/ServerBuilderTest.java

@@ -4,6 +4,8 @@
 import static io.appium.java_client.TestUtils.getLocalIp4Address;
 import static io.appium.java_client.service.local.AppiumDriverLocalService.buildDefaultService;
 import static io.appium.java_client.service.local.AppiumServiceBuilder.APPIUM_PATH;
+import static io.appium.java_client.service.local.AppiumServiceBuilder.BROADCAST_IP_ADDRESS;
+import static io.appium.java_client.service.local.AppiumServiceBuilder.DEFAULT_APPIUM_PORT;
 import static io.appium.java_client.service.local.flags.GeneralServerFlag.CALLBACK_ADDRESS;
 import static io.appium.java_client.service.local.flags.GeneralServerFlag.SESSION_OVERRIDE;
 import static io.appium.java_client.service.local.flags.GeneralServerFlag.BASEPATH;
@@ -20,6 +22,7 @@
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import com.google.common.collect.ImmutableMap;
 import io.appium.java_client.android.options.UiAutomator2Options;
@@ -55,6 +58,9 @@ public class ServerBuilderTest {
     private static final Path PATH_T0_TEST_MAIN_JS = ROOT_TEST_PATH
             .resolve("service").resolve("local").resolve("main.js");
 
+    private static final String INVALID_BASE_PATH_ERROR_MESSAGE =
+        "Given base path is not valid - blank or empty values are not allowed for base path";
+
     private static String testIP;
     private AppiumDriverLocalService service;
     private File testLogFile;
@@ -315,9 +321,54 @@ public void checkAbilityToStartServiceWithLogFileUsingShortFlag() {
     }
 
     @Test
-    public void checkAbilityToStartServiceUsingBasePath() {
-        service = new AppiumServiceBuilder().withArgument(BASEPATH, "/wd/hub").build();
+    public void checkAbilityToStartServiceUsingValidBasePathWithMultiplePathParams() {
+        String baseUrl = String.format("http://%s:%d/", BROADCAST_IP_ADDRESS, DEFAULT_APPIUM_PORT);
+        String basePath = "wd/hub";
+        service = new AppiumServiceBuilder().withArgument(BASEPATH, basePath).build();
         service.start();
         assertTrue(service.isRunning());
+        assertEquals(baseUrl + basePath + "/",service.getUrl().toString());
+    }
+
+    @Test
+    public void checkAbilityToStartServiceUsingValidBasePathWithSinglePathParams() {
+        String baseUrl = String.format("http://%s:%d/", BROADCAST_IP_ADDRESS, DEFAULT_APPIUM_PORT);
+        String basePath = "/wd/";
+        service = new AppiumServiceBuilder().withArgument(BASEPATH, basePath).build();
+        service.start();
+        assertTrue(service.isRunning());
+        assertEquals(baseUrl + basePath.substring(1) ,service.getUrl().toString());
+    }
+
+    @Test
+    public void checkAbilityToValidateBasePathForEmptyBasePath() {
+        try {
+            service = new AppiumServiceBuilder().withArgument(BASEPATH, "").build();
+            fail("Base path was not validated for Blank or Empty string");
+        } catch (Exception e) {
+            assertEquals(InvalidBasePathException.class, e.getClass());
+            assertEquals(INVALID_BASE_PATH_ERROR_MESSAGE, e.getMessage());
+        }
+    }
+
+    @Test
+    public void checkAbilityToValidateBasePathForBlankBasePath() {
+        try {
+            service = new AppiumServiceBuilder().withArgument(BASEPATH, "   ").build();
+            fail("Base path was not validated for Blank or Empty string");
+        } catch (Exception e) {
+            assertEquals(InvalidBasePathException.class, e.getClass());
+            assertEquals(INVALID_BASE_PATH_ERROR_MESSAGE, e.getMessage());
+        }
+    }
+
+    @Test
+    public void checkAbilityToValidateBasePathForNullBasePath() {
+        try {
+            service = new AppiumServiceBuilder().withArgument(BASEPATH, null).build();
+            fail("Base path was not validated for a null value");
+        } catch (Exception e) {
+            assertEquals(NullPointerException.class, e.getClass());
+        }
     }
 }