From b257a309772db2e9dfb745f97068aea6a32ca151 Mon Sep 17 00:00:00 2001
From: Meghan Denny <hello@nektro.net>
Date: Thu, 25 Apr 2024 20:49:17 -0700
Subject: [PATCH] node:fs: fix arg parsing of readSync (#10527)

---
 src/bun.js/node/node_fs.zig | 36 +++++++++++++++---------------------
 test/js/node/fs/fs.test.ts  | 13 +++++++++++++
 2 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/src/bun.js/node/node_fs.zig b/src/bun.js/node/node_fs.zig
index 06c5bbbd00..6b95b2aa25 100644
--- a/src/bun.js/node/node_fs.zig
+++ b/src/bun.js/node/node_fs.zig
@@ -2574,34 +2574,28 @@ pub const Arguments = struct {
                 if (current.isNumber() or current.isBigInt()) {
                     args.offset = current.to(u52);
 
-                    if (arguments.remaining.len < 2) {
-                        JSC.throwInvalidArguments(
-                            "length and position are required",
-                            .{},
-                            ctx,
-                            exception,
-                        );
-
+                    if (arguments.remaining.len < 1) {
+                        JSC.throwInvalidArguments("length is required", .{}, ctx, exception);
                         return null;
                     }
-                    if (arguments.remaining[0].isNumber() or arguments.remaining[0].isBigInt())
-                        args.length = arguments.remaining[0].to(u52);
 
+                    const arg_length = arguments.next().?;
+                    arguments.eat();
+
+                    if (arg_length.isNumber() or arg_length.isBigInt()) {
+                        args.length = arg_length.to(u52);
+                    }
                     if (args.length == 0) {
-                        JSC.throwInvalidArguments(
-                            "length must be greater than 0",
-                            .{},
-                            ctx,
-                            exception,
-                        );
-
+                        JSC.throwInvalidArguments("length must be greater than 0", .{}, ctx, exception);
                         return null;
                     }
 
-                    if (arguments.remaining[1].isNumber() or arguments.remaining[1].isBigInt())
-                        args.position = @as(ReadPosition, @intCast(arguments.remaining[1].to(i52)));
-
-                    arguments.remaining = arguments.remaining[2..];
+                    if (arguments.next()) |arg_position| {
+                        arguments.eat();
+                        if (arg_position.isNumber() or arg_position.isBigInt()) {
+                            args.position = @as(ReadPosition, @intCast(arg_position.to(i52)));
+                        }
+                    }
                 } else if (current.isObject()) {
                     if (current.getTruthy(ctx.ptr(), "offset")) |num| {
                         if (num.isNumber() or num.isBigInt()) {
diff --git a/test/js/node/fs/fs.test.ts b/test/js/node/fs/fs.test.ts
index b28ff5f252..5251211357 100644
--- a/test/js/node/fs/fs.test.ts
+++ b/test/js/node/fs/fs.test.ts
@@ -1044,6 +1044,19 @@ describe("readSync", () => {
     }
     closeSync(fd);
   });
+
+  it("works with offset + length passed but not position", () => {
+    const fd = openSync(import.meta.dir + "/readFileSync.txt", "r");
+    const four = new Uint8Array(4);
+    {
+      const count = readSync(fd, four, 0, 4);
+      const u32 = new Uint32Array(four.buffer)[0];
+      expect(u32).toBe(firstFourBytes);
+      expect(count).toBe(4);
+    }
+    closeSync(fd);
+  });
+
   it("works without position set", () => {
     const fd = openSync(import.meta.dir + "/readFileSync.txt", "r");
     const four = new Uint8Array(4);