From 87f4a8b4baf31d1bbe6ce080228493983c0dd6c5 Mon Sep 17 00:00:00 2001
From: Yuki Tanaka <uki00a@gmail.com>
Date: Thu, 30 Mar 2023 15:36:17 +0900
Subject: [PATCH] fix(csv/csv_stringify_stream): output headers based on
 `columns` option (#3293)

---
 csv/csv_stringify_stream.ts      | 11 +++++++++++
 csv/csv_stringify_stream_test.ts |  1 +
 2 files changed, 12 insertions(+)

diff --git a/csv/csv_stringify_stream.ts b/csv/csv_stringify_stream.ts
index 7dd80bb452d5..cf5767783f06 100644
--- a/csv/csv_stringify_stream.ts
+++ b/csv/csv_stringify_stream.ts
@@ -52,6 +52,17 @@ export class CsvStringifyStream<TOptions extends CsvStringifyStreamOptions>
 
     super(
       {
+        start(controller) {
+          if (columns && columns.length > 0) {
+            try {
+              controller.enqueue(
+                stringify([columns], { separator, headers: false }),
+              );
+            } catch (error) {
+              controller.error(error);
+            }
+          }
+        },
         transform(chunk, controller) {
           try {
             controller.enqueue(
diff --git a/csv/csv_stringify_stream_test.ts b/csv/csv_stringify_stream_test.ts
index 1fd00fd320e6..a5e18a43b227 100644
--- a/csv/csv_stringify_stream_test.ts
+++ b/csv/csv_stringify_stream_test.ts
@@ -89,6 +89,7 @@ Deno.test({
         output.push(r);
       }
       assertEquals(output, [
+        "id,name\r\n",
         "1,foo\r\n",
         "2,bar\r\n",
         "3,baz\r\n",