Bun Shell `.lines()` `AsyncIterable` returns a fake `AsyncIterator`

[MulverineX]

What version of Bun is running?

1.2.3+8c4d3ff80

What platform is your computer?

Microsoft Windows NT 10.0.22631.0 x64

What steps can reproduce the bug?

• Run an external CLI with Bun Shell that takes several seconds to run and ultimately returns a process exit code of 1 or higher.
• Use lines() to consume the shell as an AsyncIterable
• Use async_iterable[Symbol.asyncIterator]().next().then((line) => console.log('This should run, but never does:\n', line.value)).catch((err) => console.log('This shouldn\'t run on the first .next call, but does and contains the entire output', err.stdout.toString())) to demonstrate how many lines are being processed at a time.

What is the expected behavior?

Receive the first line of the CLI immediately as it is printed, never receive the error.

What do you see instead?

The entire CLI output (multiple seconds of runtime) is consumed by the one and only next() call, throwing an error with the entire stdout.

Additional information

Example implementation: https://github.com/MulverineX/extension-typescript-template/blob/f0a4c0c69a4410c00aa35e85b389dc583e8bfa5d/scripts/test.ts#L61

Further Windows Install Information:

[MulverineX]

Basically the bug here is that the Bun Shell lines() utility awaits process exit before beginning to process and return lines.

If this needs to use something other than AsyncIterable or there needs to be an alternative to lines() that would be a sufficient solution as well.

[MulverineX]

For those curious, here's an implementation with Bun Spawn that actually works:

https://github.com/MulverineX/extension-typescript-template/blob/63627a74a55e19d2b96849d8f41f1483983b8981/scripts/test.ts#L64-L101

const moodriver = Bun.spawn({
    cmd: ['moodriver', verbose ? '-vv' : '-v', '-t', `./test/${test}`, './ext.wasm'],
    stdout: 'pipe',
    windowsHide: true,
    windowsVerbatimArguments: true,
})

const reader = moodriver.stdout.getReader()

const decoder = new TextDecoder()

class ShellLine {
    constructor(public rawLine: string, public i: number, public chunkI: number, public lines: number) {}

    get line() {
        return this.rawLine.replace(/\u001b\[.*?m/g, '')
    }
}

async function* shell() {
    let done = false

    let globalI = 0

    while (!done) {
        const chunk = await reader.read()

        if (chunk.done) {
            done = true
        } else {
            let lines = decoder.decode(chunk.value).split('\n')

            for (let i = 0; i < lines.length; i++) {
                yield new ShellLine(lines[i], globalI++, i, lines.length)
            }
        }
    }
}

for await (const { line, rawLine, i, chunkI, lines } of shell()) {
    // handle lines as they come in
}

if ((await moodriver.exited) > 0) {
    // handle process exit code of 1 or higher
}

Note: I might make a library that does this for you