Ignore `ERR_STREAM_PREMATURE_CLOSE` in CLI server by JanJakes · Pull Request #3304 · WordPress/wordpress-playground

JanJakes · 2026-02-25T10:35:26Z

Motivation for the change, related issues

The streaming response refactor in #3222 replaced buffered responses with pipeline(Readable.fromWeb(stdout), res). When the browser disconnects before the response stream finishes — e.g. during a redirect or when the user clicks a link mid-load — Node.js throws ERR_STREAM_PREMATURE_CLOSE. This results in noisy error logs on every navigation in wp-admin:

Error [ERR_STREAM_PREMATURE_CLOSE]: Premature close
    at onclose (node:internal/streams/end-of-stream:171:30)
    at process.processTicksAndRejections (node:internal/process/task_queues:85:11)

Implementation details

Wrap the pipeline() call in handleStreamedResponse with a try/catch that silently ignores ERR_STREAM_PREMATURE_CLOSE and re-throws any other error.

Testing Instructions (or ideally a Blueprint)

Run npx nx test-playground-cli playground-cli --testFile=start-server.spec.ts
For manual verification:
- npx nx dev playground-cli start --login
- Click around in wp-admin — the ERR_STREAM_PREMATURE_CLOSE errors should no longer appear in the terminal

Node.js stream.pipeline throws ERR_STREAM_PREMATURE_CLOSE when the client disconnects before the response finishes streaming. This is normal during browser navigation — e.g. when following a redirect or clicking a link while a page is still loading. The error was introduced by the streaming response refactor in #3222 which replaced buffered responses with pipeline(Readable.fromWeb(), res). Catch and silently ignore this specific error code, re-throwing anything else.

Copilot

Pull request overview

This PR fixes noisy error logging caused by ERR_STREAM_PREMATURE_CLOSE exceptions when clients disconnect from the CLI server before response streams complete, which commonly occurs during navigation in wp-admin.

Changes:

Added error handling to suppress ERR_STREAM_PREMATURE_CLOSE errors in handleStreamedResponse
Added test coverage to verify client disconnects don't trigger error logs

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/playground/cli/src/start-server.ts	Wrapped `pipeline()` call in try-catch to filter out premature close errors
packages/playground/cli/tests/start-server.spec.ts	Added test that simulates client disconnect and verifies no errors are logged

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Copilot · 2026-02-25T10:36:01Z

packages/playground/cli/src/start-server.ts

+			'code' in error &&
+			error.code === 'ERR_STREAM_PREMATURE_CLOSE'


The type guard checking 'code' in error followed by accessing error.code is redundant. Since Node.js errors with a code property are typed as NodeJS.ErrnoException, you can streamline this by checking (error as NodeJS.ErrnoException).code === 'ERR_STREAM_PREMATURE_CLOSE' or using optional chaining with error.code === 'ERR_STREAM_PREMATURE_CLOSE' after the instanceof Error check.

Suggested change

'code' in error &&

error.code === 'ERR_STREAM_PREMATURE_CLOSE'

(error as NodeJS.ErrnoException).code === 'ERR_STREAM_PREMATURE_CLOSE'

The in check is a runtime type narrowing that lets TypeScript know error.code exists without an unsafe cast. (error as NodeJS.ErrnoException).code skips the runtime check and trusts the cast. Keeping as-is.

Copilot · 2026-02-25T10:36:02Z

packages/playground/cli/tests/start-server.spec.ts

+			}),
+			new ReadableStream({
+				start(controller) {
+					controller.enqueue(new TextEncoder().encode('hello'));


The stdout stream (lines 24-28) never closes its controller, which may cause the pipeline to hang indefinitely or behave unpredictably during cleanup. The test works because the client disconnects early, but this represents incomplete stream behavior. Call controller.close() after enqueueing data to properly terminate the stream.

Suggested change

controller.enqueue(new TextEncoder().encode('hello'));

controller.enqueue(new TextEncoder().encode('hello'));

controller.close();

Intentional — the test needs the stream to still be open when the client disconnects, otherwise pipeline completes normally and there is no premature close to test.

brandonpayton

Thanks for fixing this, @JanJakes! This issue is really annoying and kind of embarrassing to have littered in our output.

I left one note. Please do what you want with that and feel free to merge.

JanJakes · 2026-03-03T07:46:40Z

Thanks, @brandonpayton!

I left one note. Please do what you want with that and feel free to merge.

This may have been lost somehow. I can't find the note, unfortunately.

brandonpayton · 2026-03-03T14:54:29Z

packages/playground/cli/tests/start-server.spec.ts

+			});
+
+			await new Promise((r) => setTimeout(r, 200));
+			expect(logger.error).not.toHaveBeenCalled();


If error logging is broken completely, this test would also pass. Maybe it would be good to prove error logging is working at all so we can at least note the absence of the error in the context of working error logging.

@brandonpayton Good point! Fixed in 3d5f46b.

brandonpayton · 2026-03-03T14:55:21Z

This may have been lost somehow. I can't find the note, unfortunately.

@JanJakes apparently I forgot to submit the comment. It is now here.

Also trigger a real error through the same server to prove the logging pipeline is functional, so the prior not.toHaveBeenCalled() assertion is meaningful and not just a consequence of broken logging.

… not logged The test was only checking that logger.error was not called, but didn't verify that the ERR_STREAM_PREMATURE_CLOSE error actually occurred. This means the test could pass vacuously if the error stopped being produced. Spy on pipeline from stream/promises and assert that it rejected with ERR_STREAM_PREMATURE_CLOSE before checking logger.error was not called.

brandonpayton · 2026-03-06T22:15:10Z

I made another tweak to the test to more explicitly confirm the presence of the ignored error. It looks like we're good to go!

JanJakes requested review from Copilot and fellyph February 25, 2026 10:35

Copilot AI reviewed Feb 25, 2026

View reviewed changes

JanJakes changed the title ~~Ignore ERR_STREAM_PREMATURE_CLOSE in CLI server~~ Ignore ERR_STREAM_PREMATURE_CLOSE in CLI server Feb 25, 2026

brandonpayton approved these changes Mar 3, 2026

View reviewed changes

brandonpayton reviewed Mar 3, 2026

View reviewed changes

Verify error logging works in client disconnect test

3d5f46b

Also trigger a real error through the same server to prove the logging pipeline is functional, so the prior not.toHaveBeenCalled() assertion is meaningful and not just a consequence of broken logging.

JanJakes force-pushed the fix/cli-stream-premature-close branch from 65bd9bd to 3d5f46b Compare March 5, 2026 16:22

JanJakes requested a review from brandonpayton March 5, 2026 16:35

brandonpayton merged commit 171dfd2 into trunk Mar 6, 2026
42 checks passed

brandonpayton deleted the fix/cli-stream-premature-close branch March 6, 2026 22:15

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Ignore `ERR_STREAM_PREMATURE_CLOSE` in CLI server#3304

Ignore `ERR_STREAM_PREMATURE_CLOSE` in CLI server#3304
brandonpayton merged 3 commits intotrunkfrom
fix/cli-stream-premature-close

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		'code' in error &&
		error.code === 'ERR_STREAM_PREMATURE_CLOSE'

	'code' in error &&
	error.code === 'ERR_STREAM_PREMATURE_CLOSE'
	(error as NodeJS.ErrnoException).code === 'ERR_STREAM_PREMATURE_CLOSE'

	controller.enqueue(new TextEncoder().encode('hello'));
	controller.enqueue(new TextEncoder().encode('hello'));
	controller.close();

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JanJakes commented Feb 25, 2026

Motivation for the change, related issues

Implementation details

Testing Instructions (or ideally a Blueprint)

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Pull request overview

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