GH-9268: Fix regression in SMB Inbound for sub-dirs

Fixes: #9268

The new `SmbSession.list()` behavior prevents to pull files from sub-folders in inbound channel adapter

* Fix `SmbSession.list()` similar way to `SftpSession`: if `remoteFile.isFile()` then remove it as is.
Otherwise, perform `smbDir.listFiles()` on that sub-dir
* Modify `SmbTests.testSmbInboundFlow()` to poll files from the `smbSource/subSmbSource/`

**Auto-cherry-pick to `6.3.x` & `6.2.x`**

Author: artembilan

spring-integration-smb/src/main/java/org/springframework/integration/smb/session/SmbSession.java

@@ -119,25 +119,26 @@ public boolean remove(String _path) throws IOException {
 	}
 
 	/**
-	 * Return the contents of the specified SMB resource as an array of SmbFile objects.
+	 * Return the content of the specified SMB resource as an array of SmbFile objects.
 	 * In case the remote resource does not exist, an empty array is returned.
-	 * @param remotePath path to a remote directory or remote file path
+	 * @param path path to a remote directory or remote file path
 	 * @return array of SmbFile objects
-	 * @throws IOException on error conditions returned by a CIFS server or if the remote resource is not a directory.
+	 * @throws IOException on error conditions returned by a CIFS server.
 	 */
 	@Override
-	public SmbFile[] list(String remotePath) throws IOException {
-		SmbFile[] files;
+	public SmbFile[] list(String path) throws IOException {
+		String remotePath = StringUtils.trimTrailingCharacter(path, '/');
+		SmbFile[] files = null;
 		int lastIndex = StringUtils.hasText(remotePath) ? remotePath.lastIndexOf('/') : 0;
 		String remoteFileName = lastIndex > 0 ? remotePath.substring(lastIndex + 1) : null;
 		if (StringUtils.hasText(remoteFileName)) {
 			SmbFile remoteFile = createSmbFileObject(remotePath);
-			if (!remoteFile.isFile()) {
-				throw new IOException("[" + remotePath + "] is not a file.");
+			if (remoteFile.isFile()) {
+				files = new SmbFile[] {remoteFile};
 			}
-			files = new SmbFile[] {remoteFile};
 		}
-		else {
+
+		if (files == null) {
 			try {
 				SmbFile smbDir = createSmbDirectoryObject(remotePath);
 				if (!smbDir.exists()) {
@@ -154,6 +155,7 @@ else if (!smbDir.isDirectory()) {
 				throw new IOException("Failed to list in [" + remotePath + "].", _ex);
 			}
 		}
+
 		logListedFiles(remotePath, files);
 
 		return files;

spring-integration-smb/src/test/java/org/springframework/integration/smb/dsl/SmbTests.java

@@ -92,7 +92,7 @@ public void testSmbInboundFlow() {
 		DirectoryScanner scanner = new DefaultDirectoryScanner();
 		IntegrationFlow flow = IntegrationFlow.from(Smb.inboundAdapter(sessionFactory())
 								.preserveTimestamp(true)
-								.remoteDirectory("smbSource")
+								.remoteDirectory("smbSource/subSmbSource/")
 								.maxFetchSize(10)
 								.scanner(scanner)
 								.regexFilter(".*\\.txt$")
@@ -115,13 +115,13 @@ public void testSmbInboundFlow() {
 		Object payload = message.getPayload();
 		assertThat(payload).isInstanceOf(File.class);
 		File file = (File) payload;
-		assertThat(file.getName()).isIn("SMBSOURCE1.TXT.a", "SMBSOURCE2.TXT.a");
+		assertThat(file.getName()).isEqualTo("SUBSMBSOURCE1.TXT.a", "SUBSMBSOURCE2.TXT.a");
 		assertThat(file.getAbsolutePath()).contains("localTarget");
 
 		message = out.receive(10_000);
 		assertThat(message).isNotNull();
 		file = (File) message.getPayload();
-		assertThat(file.getName()).isIn("SMBSOURCE1.TXT.a", "SMBSOURCE2.TXT.a");
+		assertThat(file.getName()).isIn("SUBSMBSOURCE1.TXT.a", "SUBSMBSOURCE2.TXT.a");
 		assertThat(file.getAbsolutePath()).contains("localTarget");
 
 		assertThat(out.receive(10)).isNull();