@std/io: readAllSync only reads a single line from Deno.stdin when stdin is interactive

[frou]

https://jsr.io/@std/io/doc/~/readAllSync

Steps to Reproduce

#!/usr/bin/env deno run

import { readAllSync } from "@std/io"

const content = readAllSync(Deno.stdin)

console.log()
console.log(content.length)

Expected behavior

When running the above script in a shell session, I'd expect to be able to do the following (typing 3 lines then pressing Ctrl-D (i.e. EOF) to finish):

$ ./repro.ts
one
two
three
^D

14
$

That is how all the other languages I've tried work.

Describe the bug

But readAllSync returns after I type the first line.

$ ./repro.ts
one

4
$

Environment

• OS: macOS 12.7.6
• deno version: 2.1.5
• std version: 0.225.0

[kt3k]

hmm, it looks like 0 byte read is translated to null (EOF) in Deno CLI (ref: https://github.com/denoland/deno/blob/4e0bf4b093c12f6baceee960e5c07bbc13b69a1e/ext/io/12_io.js#L38 ) and that seems causing this issue. I don't think there's anything we can fix in STD.

[0f-0b]

Here's a failing test which demonstrates that this is a bug in readAllSync.

import { assertEquals } from "jsr:@std/assert@1/equals";
import {
  readAll,
  readAllSync,
  type Reader,
  type ReaderSync,
} from "jsr:@std/[email protected]";

class SlowBuffer implements Reader, ReaderSync {
  #remaining: Uint8Array;

  constructor(bytes: Uint8Array) {
    this.#remaining = bytes;
  }

  // deno-lint-ignore require-await -- implementing `Reader` interface
  async read(p: Uint8Array): Promise<number | null> {
    return this.readSync(p);
  }

  readSync(p: Uint8Array): number | null {
    if (p.length === 0) {
      throw new TypeError("p is empty");
    }
    const remaining = this.#remaining;
    if (remaining.length === 0) {
      // no more bytes to read; signal end-of-stream
      return null;
    }
    // read one byte at a time
    this.#remaining = remaining.subarray(1);
    p[0] = remaining[0];
    return 1;
  }
}

Deno.test("readAll() with SlowBuffer", async () => {
  const testBytes = crypto.getRandomValues(new Uint8Array(20));
  const reader = new SlowBuffer(testBytes);
  const actualBytes = await readAll(reader);
  assertEquals(actualBytes, testBytes);
});

Deno.test("readAllSync() with SlowBuffer", () => {
  const testBytes = crypto.getRandomValues(new Uint8Array(20));
  const reader = new SlowBuffer(testBytes);
  const actualBytes = readAllSync(reader);
  assertEquals(actualBytes, testBytes);
});

[kt3k]

Oh, this actually looks like a bug of readSyncAll. Thanks for the test case.

[kt3k]

Looks like this was introduced in #4128 when we re-implemented readAllSync without using Buffer