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Fix Bun 1.4 + pthreads by always bridging parentPort in worker threads #27582

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Fix Bun 1.4 + pthreads by always bridging parentPort in worker threads #27582

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5 changes: 1 addition & 4 deletions .circleci/config.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -805,10 +805,7 @@ jobs:
- run:
name: install bun
command: |
# Temporally pin to 1.3.14 (the last non-rust version) until we
# can investigate the breakages:
# https://github.com/emscripten-core/emscripten/issues/27580
curl -fsSL https://bun.com/install | bash -s "bun-v1.3.14"
curl -fsSL https://bun.com/install | bash
echo "BUN = '~/.bun/bin/bun'" >> ~/emsdk/.emscripten
echo "JS_ENGINES = [BUN]" >> ~/emsdk/.emscripten
- run-tests:
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9 changes: 2 additions & 7 deletions src/pthread_esm_startup.mjs
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Expand Up @@ -20,13 +20,8 @@ if ({{{ nodeDetectionCode() }}}) {
var worker_threads = await import('node:worker_threads');
globalThis.Worker = worker_threads.Worker;
var parentPort = worker_threads.parentPort;
// Deno and Bun already have `postMessage` defined on the global scope and

@dschuff dschuff Aug 21, 2026

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so this isn't a problem for deno?

@sbc100 sbc100 Aug 21, 2026

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It seems not no.

Sadly this change does beak bun < 1.4 (since it ends up delivering messages twice).. but I'm not sure we care about back compat at this point.

@guybedford guybedford Aug 21, 2026

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It seems like the original reason for the guard was fixed in denoland/deno#32596.

// deliver messages to `globalThis.onmessage`, so we must not duplicate that
// behavior here if `postMessage` is already present.
if (!globalThis.postMessage) {
parentPort.on('message', (msg) => globalThis.onmessage?.({ data: msg }));
globalThis.postMessage = (msg) => parentPort.postMessage(msg);
}
parentPort.on('message', (msg) => globalThis.onmessage?.({ data: msg }));
globalThis.postMessage = (msg) => parentPort.postMessage(msg);
}
#endif

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9 changes: 2 additions & 7 deletions src/runtime_common.js
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Original file line number Diff line number Diff line change
Expand Up @@ -39,13 +39,8 @@ if (ENVIRONMENT_IS_NODE && {{{ ENVIRONMENT_IS_WORKER_THREAD() }}}) {
// Create as web-worker-like an environment as we can.
globalThis.self = globalThis;
var parentPort = worker_threads.parentPort;
// Deno and Bun already have `postMessage` defined on the global scope and
// deliver messages to `globalThis.onmessage`, so we must not duplicate that
// behavior here if `postMessage` is already present.
if (!globalThis.postMessage) {
parentPort.on('message', (msg) => globalThis.onmessage?.({ data: msg }));
globalThis.postMessage = (msg) => parentPort.postMessage(msg);
}
parentPort.on('message', (msg) => globalThis.onmessage?.({ data: msg }));
globalThis.postMessage = (msg) => parentPort.postMessage(msg);
// Node.js Workers do not pass postMessage()s and uncaught exception events to the parent
// thread necessarily in the same order where they were generated in sequential program order.
// See https://github.com/nodejs/node/issues/59617
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8 changes: 4 additions & 4 deletions test/codesize/test_codesize_minimal_pthreads.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 6883,
"a.out.js.gz": 3422,
"a.out.js": 6857,
"a.out.js.gz": 3416,
"a.out.nodebug.wasm": 19132,
"a.out.nodebug.wasm.gz": 8845,
"total": 26015,
"total_gz": 12267,
"total": 25989,
"total_gz": 12261,
"sent": [
"a (memory)",
"b (exit)",
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8 changes: 4 additions & 4 deletions test/codesize/test_codesize_minimal_pthreads_memgrowth.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 7341,
"a.out.js.gz": 3639,
"a.out.js": 7315,
"a.out.js.gz": 3633,
"a.out.nodebug.wasm": 19133,
"a.out.nodebug.wasm.gz": 8846,
"total": 26474,
"total_gz": 12485,
"total": 26448,
"total_gz": 12479,
"sent": [
"a (memory)",
"b (exit)",
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