stream/iter: merge() treats valid object-like sources as options

[trivikr]

Version

26.1.0

Platform

macOS 26.5.0

Subsystem

stream

What steps will reproduce the bug?

import assert from 'node:assert/strict';
import { from, merge, text, toStreamable } from 'node:stream/iter';

const arrayBuffer = new TextEncoder().encode('abc').buffer;
const protocolObject = {
  [toStreamable]() {
    return 'abc';
  },
};

assert.deepStrictEqual({
  directArrayBuffer: await text(from(arrayBuffer)),
  mergedArrayBuffer: await text(merge(arrayBuffer)),
  directProtocol: await text(from(protocolObject)),
  mergedProtocol: await text(merge(protocolObject)),
}, {
  directArrayBuffer: 'abc',
  mergedArrayBuffer: 'abc',
  directProtocol: 'abc',
  mergedProtocol: 'abc',
});

Run with

node --experimental-stream-iter --no-warnings repro.mjs

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior? Why is that the expected behavior?

No assertion error.

merge(source) should accept the same valid object-like sources as from(source), including ArrayBuffer and Stream.toStreamable objects.

What do you see instead?

Assertion error

node:internal/modules/run_main:107
    triggerUncaughtException(
    ^

AssertionError [ERR_ASSERTION]: Expected values to be strictly deep-equal:
+ actual - expected

  {
    directArrayBuffer: 'abc',
    directProtocol: 'abc',
+   mergedArrayBuffer: '',
+   mergedProtocol: ''
-   mergedArrayBuffer: 'abc',
-   mergedProtocol: 'abc'
  }

    at file:///Users/trivikram/workspace/test-repro/repro.js:11:8
    at process.processTicksAndRejections (node:internal/process/task_queues:104:5) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: {
    directArrayBuffer: 'abc',
    mergedArrayBuffer: '',
    directProtocol: 'abc',
    mergedProtocol: ''
  },
  expected: {
    directArrayBuffer: 'abc',
    mergedArrayBuffer: 'abc',
    directProtocol: 'abc',
    mergedProtocol: 'abc'
  },
  operator: 'deepStrictEqual',
  diff: 'simple'
}

merge() classifies the final non-iterable object as options, drops it from sources, and returns '' for those cases.

Additional information

No response