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isPaused returned m_paused, which pause() sets even when it returns false and which nothing clears when the connection goes away. On a closed, terminated, or failed socket, pause() returned false and isPaused became true. A pause latched while CONNECTING stayed true after the connection failed. isPaused now also requires a socket the pause applies to: a connected one, or a CONNECTING one that applies the latch when it opens.
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Status: the fix is in this PR. How I reproduced it. On 1.4.3-canary.1 (Linux x64), open a client The 12 new tests in |
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ChangesWebSocket pause lifecycle
Priority: ⬇️ Low Merge Risk: ⚪ Minimal · up to The pause state remains effective while a connection is opening or open and is inactive after connection loss. No merge-blocking issue was identified. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@test/js/web/websocket/websocket-pause.test.ts`:
- Line 447: Replace the parameterized lifecycle tests using it.each() with a
single describe.each(cases) block, containing nested it() tests for the “never
paused” and corresponding second lifecycle assertions. Keep each case’s
assertions grouped together and preserve the existing test behavior.
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src/jsc/bindings/webcore/WebSocket.htest/js/web/websocket/websocket-pause.test.ts
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Updated 2:28 PM PT - Sep 16th, 2026
✅ @robobun, your commit b2519c23d44e7bc326c5d906585d0f9353de3c18 passed in 🧪 To try this PR locally: bunx bun-pr 42978That installs a local version of the PR into your bun-42978 --bun |
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline test nit, I also checked whether masking m_paused at the getter (instead of clearing it on teardown) can leak a stale latch into a later connection: the only consumer of the raw flag is didConnect() (WebSocket.cpp:1523), which runs at most once per WebSocket instance since the client never reconnects, and both teardown paths (didClose, didFailWithErrorCode) reset m_connectedWebSocketKind to None before any state the tests observe.
Extended reasoning...
The change is a one-line C++ getter plus a parameterized test block. The design question the PR raises (mask at the getter vs. clear on each disconnect path) was traced through WebSocket.cpp: m_paused is read raw only in didConnect() for the CONNECTING latch and in applyPauseToConnectedClient(), and a WebSocket instance connects at most once, so a stale m_paused after teardown has no consumer that could re-apply it. didClose (line 1469) and didFailWithErrorCode (line 1542) both set m_connectedWebSocketKind = None before firing events, and m_state leaves CONNECTING on the failed-handshake and close-before-open paths, so the new getter reports false in every case the tests exercise. Nothing beyond the inline finding warranted a further comment.
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LGTM — the one-line getter change makes isPaused agree with what pause() returns, and b2519c2 addresses the earlier note about the open promise never rejecting.
What was reviewed:
- Traced
m_connectedWebSocketKind/m_statethroughclose(),terminate(),failConnectingWebSocket(),didClose(),didFailWithErrorCode(),cancelConnectedClient()andstop():isPausedis now false exactly in the states whereapplyPauseToConnectedClient()returns false (kindNoneand notCONNECTING), sopause() === falseimpliesisPaused === falseon every path. - The CLOSING window after
close()on an OPEN socket keeps the kind set, soisPausedcan still be true there — consistent withpause()still reaching the native client in that window. - Checked
src/js/thirdparty/ws.js: the shim reads its own#pausedflag, not the native getter, so npmwssemantics are unchanged;bun.d.tsanddocs/runtime/http/websockets.mdxalready describeisPausedas the current state. - Test block: each of the 12 cases would fail on main (either the latched
m_pausedor thepause()write leaks intoisPaused), and every wait is event-driven withusingdisposal of the server.
Extended reasoning...
Overview
The PR changes a single inline getter in /home/claude/bun/src/jsc/bindings/webcore/WebSocket.h so isPaused() returns m_paused && (m_connectedWebSocketKind != None || m_state == CONNECTING) instead of the raw m_paused flag, and adds a describe.each block of 12 tests to /home/claude/bun/test/js/web/websocket/websocket-pause.test.ts covering six ways a socket loses its connection, each run with and without a prior pause(). pause()/resume() and all state-transition code in WebSocket.cpp are untouched.
Security risks
None. The change is a read-only predicate over two existing member fields; it does not touch memory ownership, threading, user-controlled input parsing, or any network-facing code path. No new allocations, no new JS entry points, no exception-scope implications.
Level of scrutiny
Low-to-moderate. The code change is trivially small, but its correctness depends on the invariant that m_connectedWebSocketKind is cleared on every path where the native client goes away. I read close(), terminate(), failConnectingWebSocket(), cancelConnectedClient(), didClose(), didFailWithErrorCode() and stop() in WebSocket.cpp and confirmed the new predicate is exactly the negation of the false branch of applyPauseToConnectedClient(), so the stated rule (pause() === false implies isPaused === false) holds structurally rather than by case-by-case clearing. The one deliberate window where the kind is not cleared (CLOSING after close() on an OPEN socket, per the comment at WebSocket.cpp:864-867) keeps isPaused true only while pause() still acts on the native client, which is consistent. The behavior change for a socket paused while OPEN and then closed (now reports false) diverges from npm ws, but the in-tree ws shim keeps its own #paused flag and does not read the native getter, and the existing .d.ts/docs describe isPaused as the current state, so no doc or type update is needed.
Other factors
The prior inline note from the earlier review (open promise never rejected on a failed upgrade in the OPEN cases) was addressed in b2519c2 by rejecting from onclose before open. The CodeRabbit inline thread was resolved by a non-author. The changed files are not covered by CODEOWNERS. I was unable to execute the test file in this environment, so the claim that all 12 tests fail on main is verified by reasoning only: on main, pause() unconditionally sets m_paused = true and the getter returns it, so isPausedAfterPause would be true in every "never paused" case and isPaused would be true in every "paused first" case. The test block is serial rather than describe.concurrent, but each case is a single local Bun.serve plus one client and should be well within the file budget. The one added header comment is a single line explaining why the getter is not simply m_paused, which is information a reader would otherwise need to reconstruct from WebSocket.cpp.
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Heads-up from #42974 (the |
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Problem
WebSocket,pause()returnsfalseon a socket with no connection, butisPausedbecomestrue. This happens afterclose(),terminate(), and a failed connection.pause()made while the socket connects leavesisPaused === trueafter the connection fails, although it never stopped a read.isPaused()(src/jsc/bindings/webcore/WebSocket.h:193) returnsm_paused.pause()setsm_pausedeven when it returnsfalse, and nothing clears it when the connection goes away.Fix
isPaused()returnsm_pausedonly while a socket exists that the pause applies to: a connected socket, or aCONNECTINGsocket that pauses when it opens.pause()returnsfalsein exactly the other states (WebSocket.cpp:900), sopause() === falsenow impliesisPaused === false.OPENreportsfalseafter it closes. Thewsshim keeps its own flag, so it is not affected.test/js/web/websocket/websocket-pause.test.ts(the 12 new tests fail without the fix), plus eight related suites (see Notes).Background
pause(),resume(), andisPausedare Bun extensions on the clientWebSocket(WebSocket client: pause()/resume(), working bufferedAmount, and a ServerWebSocket drain stall fix #40566).pause()stops socket reads, so the peer sees TCP backpressure.m_connectedWebSocketKindnames the native client that owns the socket. It isNonebefore the open and after the connection is gone.pause()on aCONNECTINGsocket setsm_paused.didConnect()readsm_pausedand pauses the new socket.Notes
Repro (1.4.3-canary.1, Linux x64):
With this change the last value is
false.History. #40566 added the three members. The review bot reported this defect on that PR (
WebSocket.cpp:896) after it merged, and the comment got no reply. The existing test "a latched pause is dropped when the connection fails" asserts the return values only, notisPaused.Why the getter. The rule "paused implies a socket" spans two pieces of state:
m_paused, and whether a socket exists. The connection can go away in four places (didClose,didFailWithErrorCode,failConnectingWebSocket,cancelConnectedClient). A clear ofm_pausedin each of them is easy to miss in a new path. The getter is the one place that sees both facts.m_pausedstays the last request, anddidConnect()still reads it for the latch.Why
pause()andresume()are unchanged. With the new getter a script cannot see the write thatpause()makes on a socket with no connection. On main the native client does not refuse apause()while C++ holds it:pause_stream()(src/uws_sys/socket.rs:500) returnstruefor the adopted socket. So a guard inpause()has no reachable case and no test can cover it.resume()on a socket with no connection returnsfalse, andisPausedisfalsebefore and after the call.The
wspackage. npmwskeepsisPaused === trueafter a socket that was paused closes, and ignorespause()while it connects. Bun'swsshim (src/js/thirdparty/ws.js) tracks its own#pausedflag with those rules and does not read the nativeisPaused, so its behavior does not change.Relation to #42974. That PR makes
close()resume a paused socket, and makes the nativepause()returnfalsewhile a Close frame waits behind unsent data. In that window C++ still holds the native client. If #42974 merges first, I will rebase this PR so thatisPaused()keys onm_state(OPENorCONNECTING) there, with a test for that window. On main today a socket in that window can still be paused, so the check on the native client is the correct one.Tests. The new block runs six ways to lose the connection (close, terminate before and after the close event, a 403,
close()andterminate()before open). Each runs twice: never paused, and paused first (whileOPEN, or latched whileCONNECTING). Each test asserts thereadyStateit expects, thenisPaused,pause(),isPaused,resume(),isPaused. All 12 fail on 1.4.3-canary.1 and on a debug build of main, and pass with the fix. The block is at the end of the file and touches no existing test, so it does not overlap the hunks of #41109.Suites run on a debug (ASAN) build, all pass:
websocket-pause,websocket-close-connecting,websocket-close-async-dispatch,websocket-buffered-amount,websocket-client,websocket-proxy,error-event,websocket-upgrade, andtest/js/first_party/ws/ws.test.ts(184 pass, 4 skip, 0 fail).Self-review. A first version guarded
pause(), dropped the latch in two places, keptisPaused === truefor a socket that was paused and then closed, and added docs text. The review raised 6 concerns:pause() === falsewithisPaused === true. Addressed: the getter makes the rule hold in every state.resume()returnedfalsebut changed the flag, which is the opposite of npmws, and a test pinned it. Addressed:isPausedis alreadyfalsethere, and that test is gone..d.tstext froze corner rules that no maintainer chose. Addressed: this PR changes no docs.[human-review] gate passed · iteration 0 · 2 files touched
fails on main (without fix)
passes on PR (with fix)
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