Address review comments: fix documentation error codes, add thread-safety, expand test coverage

ballerina/tests/service_config_test.bal

@@ -467,3 +467,106 @@ public function testServiceConfigRelativePath() {
 
     test:assertEquals(relativeConfig.path, "relative/path");
 }
+
+// ===========================================================================
+// TEST: Invalid regex pattern in @ServiceConfig fileNamePattern
+// ===========================================================================
+@test:Config {}
+public function testServiceConfigInvalidFileNamePattern() returns error? {
+    ListenerConfiguration config = {
+        protocol: FTP,
+        host: "127.0.0.1",
+        port: 21212,
+        auth: {credentials: {username: "wso2", password: "wso2123"}},
+        pollingInterval: 2
+    };
+    Listener ftpListener = check new (config);
+
+    Service invalidRegexService = @ServiceConfig {
+        path: "/home/in/invalid-regex",
+        fileNamePattern: "[unclosed"  // Invalid regex - unclosed bracket
+    } service object {
+        remote function onFileChange(Caller caller, WatchEvent & readonly event) {
+        }
+    };
+
+    error? result = ftpListener.attach(invalidRegexService, "invalidRegexService");
+    test:assertTrue(result is InvalidConfigError,
+        msg = "Expected InvalidConfigError for invalid regex pattern in @ServiceConfig.fileNamePattern");
+    if result is InvalidConfigError {
+        test:assertTrue(result.message().includes("Invalid regex pattern"),
+            msg = "InvalidConfigError message should indicate invalid regex");
+    }
+}
+
+// ===========================================================================
+// TEST: Invalid regex pattern in @ServiceConfig fileDependencyConditions targetPattern
+// ===========================================================================
+@test:Config {}
+public function testServiceConfigInvalidTargetPattern() returns error? {
+    ListenerConfiguration config = {
+        protocol: FTP,
+        host: "127.0.0.1",
+        port: 21212,
+        auth: {credentials: {username: "wso2", password: "wso2123"}},
+        pollingInterval: 2
+    };
+    Listener ftpListener = check new (config);
+
+    Service invalidTargetService = @ServiceConfig {
+        path: "/home/in/invalid-target",
+        fileDependencyConditions: [
+            {
+                targetPattern: "(invalid*regex",  // Invalid regex - unclosed parenthesis
+                requiredFiles: ["data.txt"]
+            }
+        ]
+    } service object {
+        remote function onFileChange(Caller caller, WatchEvent & readonly event) {
+        }
+    };
+
+    error? result = ftpListener.attach(invalidTargetService, "invalidTargetService");
+    test:assertTrue(result is InvalidConfigError,
+        msg = "Expected InvalidConfigError for invalid regex pattern in @ServiceConfig.fileDependencyConditions.targetPattern");
+    if result is InvalidConfigError {
+        test:assertTrue(result.message().includes("Invalid regex pattern"),
+            msg = "InvalidConfigError message should indicate invalid regex");
+    }
+}
+
+// ===========================================================================
+// TEST: Invalid regex pattern in @ServiceConfig fileDependencyConditions requiredFiles
+// ===========================================================================
+@test:Config {}
+public function testServiceConfigInvalidRequiredFilesPattern() returns error? {
+    ListenerConfiguration config = {
+        protocol: FTP,
+        host: "127.0.0.1",
+        port: 21212,
+        auth: {credentials: {username: "wso2", password: "wso2123"}},
+        pollingInterval: 2
+    };
+    Listener ftpListener = check new (config);
+
+    Service invalidRequiredService = @ServiceConfig {
+        path: "/home/in/invalid-required",
+        fileDependencyConditions: [
+            {
+                targetPattern: "data.*\\.csv",
+                requiredFiles: ["[broken-regex"]  // Invalid regex - unclosed bracket
+            }
+        ]
+    } service object {
+        remote function onFileChange(Caller caller, WatchEvent & readonly event) {
+        }
+    };
+
+    error? result = ftpListener.attach(invalidRequiredService, "invalidRequiredService");
+    test:assertTrue(result is InvalidConfigError,
+        msg = "Expected InvalidConfigError for invalid regex pattern in @ServiceConfig.fileDependencyConditions.requiredFiles");
+    if result is InvalidConfigError {
+        test:assertTrue(result.message().includes("Invalid regex pattern"),
+            msg = "InvalidConfigError message should indicate invalid regex");
+    }
+}

native/src/main/java/io/ballerina/stdlib/ftp/transport/server/connector/contractimpl/MultiPathServerConnector.java

@@ -47,8 +47,8 @@ public class MultiPathServerConnector implements RemoteFileSystemServerConnector
     private final Map<String, RemoteFileSystemConsumer> pathConsumers = new ConcurrentHashMap<>();
     private final Map<String, Object> baseProperties;
     private AtomicBoolean isPollOperationOccupied = new AtomicBoolean(false);
-    private FileSystemManager fileSystemManager;
-    private FileSystemOptions fileSystemOptions;
+    private volatile FileSystemManager fileSystemManager;
+    private volatile FileSystemOptions fileSystemOptions;
 
     public MultiPathServerConnector(Map<String, Object> baseProperties, FtpListener ftpListener) {
         this.baseProperties = new HashMap<>(baseProperties);