BufReader's interface is un-idiomatic javascript.

[piscisaureus]

Currently BufReader.readLine(), readSlice(), peek() etc return a Promise resolving to a [result, BufState] tuple, where BufState is non-null if an error condition has occurred.

The exact definition of BufState is:

export type BufState =
  | null
  | "EOF"
  | "BufferFull"
  | "ShortWrite"
  | "NoProgress"
  | Error;

(Note that some of these BufState values aren't applicable to BufReaders; they're only applicable to BufWriters.)

This may be idiomatic in go (which doesn't have exceptions), but it's highly un-idiomatic in javascript.

I'd propose to change these interfaces as such:

• These functions return a Promise<T | null>
• On actual errors, the promise is rejected with an actual Error object.
• On EOF, the promise is resolved with null.
• Otherwise, the promise is resolved with just an Uint8Array or a string.
• The BufState type is made private or removed entirely.

cc @ry

[ry]

SGTM