Deno v0.41.0 regression: readAllSync returns zero bytes reading from stdin

[srackham]

Deno.readAllSync(Deno.stdin) always returns a zero length array, for example:

$ deno --version
deno 0.41.0
v8 8.2.308
typescript 3.8.3

$ echo Hello | deno eval "console.log(Deno.readAllSync(Deno.stdin))"
Uint8Array(0) []

I verified this behaviour on Ubuntu 18.04 and Windows 10.

The issue does does not occur in Deno v0.40.0

[ry]

Thanks for the report. Almost certainly introduced in #4762.

[ccheng]

hmm, this is probably related: readSync not allowed on stdin:

$ deno --version
deno 0.41.0
v8 8.2.308
typescript 3.8.3

$ deno eval "Deno.stdin.readSync(new Uint8Array(1000))"
error: Uncaught TypeError: sync read not allowed on this resource  
► $deno$/ops/dispatch_minimal.ts:63:11
    at unwrapResponse ($deno$/ops/dispatch_minimal.ts:63:11)
    at Object.sendSyncMinimal ($deno$/ops/dispatch_minimal.ts:118:10)
    at Object.readSync ($deno$/ops/io.ts:20:17)
    at File.readSync ($deno$/files.ts:101:12)

I verified this readSync and the readAllSync behaviours on Ubuntu 19.10 and Mac 10.12, and that they did not occur in Deno v0.40.0.

Although this readSync issue didn't occur in Deno v0.40.0, I was encountering a problem where if Deno.stdin.readSync was called about 55-ish times, Deno freezes using 100% CPU...

[ccheng]

So I tested in Deno v0.39.0, and found Deno.stdin.readSync works correctly.

I mentioned that in Deno v0.40.0, if Deno.stdin.readSync was called about 55-ish times, Deno freezes using 100% CPU. And in v0.41.0, it throws a Uncaught TypeError: sync read not allowed on this resource.

I'm only guessing the readSync and readAllSync issues are related. If it's not, I can open a new issue for it. Thanks!

[SyrupThinker]

deno/cli/js/buffer.ts

Lines 180 to 192 in 93c2164

	try {
	const i = this.#grow(MIN_READ);
	this.#reslice(i);
	const fub = new Uint8Array(this.#buf.buffer, i);
	const nread = r.readSync(fub);
	if (nread === null) {
	return n;
	}
	this.#reslice(i + nread);
	n += nread;
	} catch (e) {
	return n;
	}

@bartlomieju What is the reason for suppressing exceptions here?
The intend I assume is to be able to get the result of a partial throwing read, but it
currently masks the TypeError: sync read not allowed on this resource
error when synchronously reading on stdin.

[bartlomieju]

@SyrupThinker I'm not sure, please open a separate issue for that, seems like a bug.