Backport to branch(3.16) : Fix --no-header option not working for CSV exports (#3060)

Co-authored-by: inv-jishnu <31100916+inv-jishnu@users.noreply.github.com>

Author: feeblefakie

data-loader/core/src/main/java/com/scalar/db/dataloader/core/dataexport/CsvExportManager.java

@@ -38,9 +38,11 @@ public CsvExportManager(
   @Override
   void processHeader(ExportOptions exportOptions, TableMetadata tableMetadata, Writer writer)
       throws IOException {
-    String header = createCsvHeaderRow(exportOptions, tableMetadata);
-    writer.append(header);
-    writer.flush();
+    if (!exportOptions.isExcludeHeaderRow()) {
+      String header = createCsvHeaderRow(exportOptions, tableMetadata);
+      writer.append(header);
+      writer.flush();
+    }
   }
 
   /**

data-loader/core/src/test/java/com/scalar/db/dataloader/core/dataexport/CsvExportManagerTest.java

@@ -14,6 +14,7 @@
 import com.scalar.db.io.Column;
 import com.scalar.db.io.IntColumn;
 import com.scalar.db.io.Key;
+import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.IOException;
@@ -129,4 +130,72 @@ void startExport_givenPartitionKey_shouldGenerateOutputFile()
     Assertions.assertTrue(file.exists());
     Assertions.assertTrue(file.delete());
   }
+
+  @Test
+  void startExport_givenNoHeaderRequired_shouldGenerateOutputFileWithoutHeader() throws Exception {
+    String expectedFirstLine =
+        "9007199254740992,2147483647,true,0.000000000000000000000000000000000000000000001401298464324817,0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000049,test value,YmxvYiB0ZXN0IHZhbHVl,2000-01-01,01:01:01,2000-01-01T01:01,1970-01-21T03:20:41.740Z";
+
+    runExportAndAssertFirstLine(true, expectedFirstLine);
+  }
+
+  @Test
+  void startExport_givenHeaderRequired_shouldGenerateOutputFileWithHeader() throws Exception {
+    String expectedFirstLine = "col1,col2,col3,col4,col5,col6,col7,col8,col9,col10,col11";
+
+    runExportAndAssertFirstLine(false, expectedFirstLine);
+  }
+
+  private void runExportAndAssertFirstLine(boolean excludeHeader, String expectedFirstLine)
+      throws Exception {
+    // Arrange
+    producerTaskFactory = new ProducerTaskFactory(",", false, false);
+    exportManager = new CsvExportManager(storage, dao, producerTaskFactory);
+    Scanner scanner = Mockito.mock(Scanner.class);
+    String filePath = Paths.get("").toAbsolutePath() + "/output.csv";
+    Map<String, Column<?>> values = UnitTestUtils.createTestValues();
+    Result result = new ResultImpl(values, mockData);
+    List<Result> results = Collections.singletonList(result);
+
+    ExportOptions exportOptions =
+        ExportOptions.builder(
+                "namespace",
+                "table",
+                Key.newBuilder().add(IntColumn.of("col1", 1)).build(),
+                FileFormat.CSV)
+            .sortOrders(Collections.emptyList())
+            .scanRange(new ScanRange(null, null, false, false))
+            .delimiter(",")
+            .excludeHeaderRow(excludeHeader)
+            .build();
+
+    Mockito.when(
+            dao.createScanner(
+                exportOptions.getNamespace(),
+                exportOptions.getTableName(),
+                exportOptions.getScanPartitionKey(),
+                exportOptions.getScanRange(),
+                exportOptions.getSortOrders(),
+                exportOptions.getProjectionColumns(),
+                exportOptions.getLimit(),
+                storage))
+        .thenReturn(scanner);
+    Mockito.when(scanner.iterator()).thenReturn(results.iterator());
+    try (BufferedWriter writer =
+        Files.newBufferedWriter(
+            Paths.get(filePath),
+            Charset.defaultCharset(),
+            StandardOpenOption.CREATE,
+            StandardOpenOption.TRUNCATE_EXISTING)) {
+      exportManager.startExport(exportOptions, mockData, writer);
+    }
+    File file = new File(filePath);
+    Assertions.assertTrue(file.exists());
+    try (BufferedReader br = Files.newBufferedReader(file.toPath(), Charset.defaultCharset())) {
+      String firstLine = br.readLine();
+      Assertions.assertEquals(expectedFirstLine, firstLine);
+    } finally {
+      Assertions.assertTrue(file.delete());
+    }
+  }
 }