stream: fix uncatchable error closing a half-open Duplex.toWeb()

[3zrv]

Fixes: #64120

What: Fix an uncatchable TypeError: Cannot read properties of undefined (reading 'error') thrown from internal/webstreams/adapters when closing the writable side of a half-open Duplex.toWeb() (e.g. a net socket whose peer sent FIN).

Why: The writable adapter's close() has an else-branch (taken when writableEnded is already true) that sets controller = undefined but does not detach the eos listener. When the underlying writable's finish/close fires afterward, the eos callback runs controller.error(new AbortError()) on the now-undefined controller and throws. Because the throw happens synchronously inside the finish event emit (not in the close() promise chain), user try/catch around writer.close() cannot catch it and the process crashes.

This was latent until v26.3.0. Commit cbee0de (align Readable.toWeb termination with eos) made the readable side's eos use writable: false, so reader.read() now resolves on the readable END before the writable FINISH. With allowHalfOpen: false, that lands writer.close() in the exact window where writableEnded === true but writableFinished === false, triggering the null-deref.

How: Guard both controller.error(...) calls in the eos callback with optional chaining (controller?.error(...)), completing the intent that the controller is inert once close() clears it. The eos listener is intentionally kept attached so its error-handling safety net still swallows any post-close error rather than letting that become uncaught. Adds a deterministic, network-free regression test (a Duplex with allowHalfOpen: false and a final() that defers finish to a macrotask).

[mcollina]

lgtm

[mcollina]

Can you add the DCO signoff?

[3zrv]

I think my commit already has it

Signed-off-by: Mohamed Sayed k@3zrv.com

Unless there's something I missed

[jazelly]

lgtm! Can you please amend your first commit message? The title needs to be less than 72 chars.

[mcollina]

lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74472/

[mcollina]

@nodejs/platform-windows @nodejs/build can you take a look at why this test is now failing on Windows (https://ci.nodejs.org/job/node-test-binary-windows-js-suites/41387/RUN_SUBSET=1,nodes=win10-COMPILED_BY-vs2022_clang/testReport/junit/(root)/parallel/test_path_win32_normalize_device_names/):

---
duration_ms: 222.997
exitcode: 1
severity: fail
stack: |-
  node:internal/assert/utils:146
    throw error;
    ^

  AssertionError [ERR_ASSERTION]: path.win32.normalize("COM9.") === ".\\COM9.", but got "COM9."
  + actual - expected

  + 'COM9.'
  - '.\\COM9.'

      at Object.<anonymous> (c:\workspace\node-test-binary-windows-js-suites\node\test\parallel\test-path-win32-normalize-device-names.js:114:10)
      at Module._compile (node:internal/modules/cjs/loader:1947:14)
      at Object..js (node:internal/modules/cjs/loader:2087:10)
      at Module.load (node:internal/modules/cjs/loader:1669:32)
      at Module._load (node:internal/modules/cjs/loader:1450:12)
      at wrapModuleLoad (node:internal/modules/cjs/loader:260:19)
      at Module.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:154:5)
      at node:internal/main/run_main_module:33:47 {
    generatedMessage: false,
    code: 'ERR_ASSERTION',
    actual: 'COM9.',
    expected: '.\\COM9.',
    operator: 'strictEqual',
    diff: 'simple'
  }

  Node.js v27.0.0-pre
...

This PR is absolutely not related.

[targos]

You need c4429c8 (rerunning a full CI should rebase and include it)

[3zrv]

should be good now

[mcollina]

lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74658/

[nodejs-github-bot]

Commit Queue failed

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----------------------------------- PR info ------------------------------------
Title      stream: fix uncatchable error closing a half-open Duplex.toWeb() (#64161)
   ⚠  Could not retrieve the email or name of the PR author's from user's GitHub profile!
Branch     3zrv:fix/half-open-duplex-error-catch -> nodejs:main
Labels     author ready, web streams
Commits    2
 - stream: fix uncatchable error closing half-open Duplex.toWeb() writable
 - Merge branch 'main' into fix/half-open-duplex-error-catch
Committers 1
 - Mohamed Sayed <k@3zrv.com>
PR-URL: https://github.com/nodejs/node/pull/64161
Fixes: https://github.com/nodejs/node/issues/64120
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Jason Zhang <xzha4350@gmail.com>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/64161
Fixes: https://github.com/nodejs/node/issues/64120
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Jason Zhang <xzha4350@gmail.com>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Sat, 27 Jun 2026 02:53:50 GMT
   ✔  Approvals: 2
   ✔  - Matteo Collina (@mcollina) (TSC): https://github.com/nodejs/node/pull/64161#pullrequestreview-4609329978
   ✔  - Jason Zhang (@jazelly): https://github.com/nodejs/node/pull/64161#pullrequestreview-4591853232
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error: commit 89be1dc513bc4fe548301d5e6c48920723c35755 is a merge but no -m option was given.
fatal: cherry-pick failed
[main d46f5d2e64] stream: fix uncatchable error closing half-open Duplex.toWeb() writable
 Author: Mohamed Sayed <k@3zrv.com>
 Date: Sat Jun 27 05:44:35 2026 +0300
 2 files changed, 27 insertions(+), 2 deletions(-)
   ✘  Failed to apply patches

https://github.com/nodejs/node/actions/runs/28949193825