Update fs.js

Close: https://github.com/oven-sh/bun/issues/3395

src/js/node/fs.js

@@ -642,8 +642,8 @@ WriteStream = (function (InternalWriteStream) {
   });
 
   return Object.defineProperty(
-    function WriteStream(options) {
-      return new InternalWriteStream(options);
+    function WriteStream(path, options) {
+      return new InternalWriteStream(path, options);
     },
     Symbol.hasInstance,
     {

src/js/out/modules/node/fs.js

@@ -366,8 +366,8 @@ WriteStream = function(InternalWriteStream) {
   return WriteStreamClass = InternalWriteStream, Object.defineProperty(WriteStreamClass.prototype, Symbol.toStringTag, {
     value: "WritesStream",
     enumerable: !1
-  }), Object.defineProperty(function WriteStream(options) {
-    return new InternalWriteStream(options);
+  }), Object.defineProperty(function WriteStream(path, options) {
+    return new InternalWriteStream(path, options);
   }, Symbol.hasInstance, {
     value(instance) {
       return instance instanceof InternalWriteStream;

test/js/node/fs/fs.test.ts

@@ -1068,6 +1068,44 @@ describe("createWriteStream", () => {
       expect(exception.code).toBe("ERR_INVALID_ARG_TYPE");
     }
   });
+
+  it("writing in append mode should not truncate the file", async () => {
+    const path = `${tmpdir()}/fs.test.js/${Date.now()}.createWriteStreamAppend.txt`;
+    const stream = createWriteStream(path, {
+      // @ts-ignore-next-line
+      flags: "a",
+    });
+    stream.write("first line\n");
+    stream.end();
+
+    await new Promise((resolve, reject) => {
+      stream.on("error", e => {
+        reject(e);
+      });
+
+      stream.on("finish", () => {
+        resolve(true);
+      });
+    });
+
+    const stream2 = createWriteStream(path, {
+      // @ts-ignore-next-line
+      flags: "a",
+    });
+    stream2.write("second line\n");
+    stream2.end();
+
+    return await new Promise((resolve, reject) => {
+      stream2.on("error", e => {
+        reject(e);
+      });
+
+      stream2.on("finish", () => {
+        expect(readFileSync(path, "utf8")).toBe("first line\nsecond line\n");
+        resolve(true);
+      });
+    });
+  });
 });
 
 describe("fs/promises", () => {