node:fs: fix arg parsing of readSync (#10527)

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);
 
- if (args.length == 0) {
- JSC.throwInvalidArguments(
- "length must be greater than 0",
- .{},
- ctx,
- exception,
- );
+ 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);
  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()) {

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);