Fix multithreading to work in Deno and Bun (#25947)

Projects using Emscripten with pthreads don't work in Deno or Bun
because those runtimes implement Web Worker APIs that Node doesn't, and
Emscripten attempts to re-implement those APIs when running in
Node/Deno/Bun in a way that conflicts with Deno and Bun's own
implementations. This PR feature-detects Deno and Bun's `postMessage`
implementation and avoids setting up its own conflicting implementation
in that case.

Fixes: denoland/deno#17171

---------

Co-authored-by: Alon Zakai <[email protected]>

Author: Macil

.circleci/config.yml

@@ -873,6 +873,8 @@ jobs:
       - upload-test-results
   test-bun:
     executor: linux-python
+    environment:
+      OVERRIDE_NODE_JS_TEST_VERSION: "v24.0.0"
     steps:
       - checkout
       - pip-install
@@ -881,10 +883,14 @@ jobs:
           name: install bun
           command: |
             curl -fsSL https://bun.com/install | bash
-            echo "BUN_ENGINE = os.path.expanduser('~/.bun/bin/bun')" >> ~/emsdk/.emscripten
-            echo "JS_ENGINES = [BUN_ENGINE]" >> ~/emsdk/.emscripten
+            echo "NODE_JS_TEST = os.path.expanduser('~/.bun/bin/bun')" >> ~/emsdk/.emscripten
+            echo "JS_ENGINES = [NODE_JS_TEST]" >> ~/emsdk/.emscripten
       - run-tests:
-          test_targets: "core0.test_hello_world"
+          test_targets: "
+            core0.test_hello_world
+            core0.test_hello_argc_pthreads
+            core2.test_pthread_create
+            "
   test-jsc:
     executor: linux-python
     steps:

src/pthread_esm_startup.mjs

@@ -16,14 +16,17 @@ console.log("Running pthread_esm_startup");
 #if ENVIRONMENT_MAY_BE_NODE
 if ({{{ nodeDetectionCode() }}}) {
   // Create as web-worker-like an environment as we can.
+  globalThis.self = globalThis;
   var worker_threads = await import('worker_threads');
-  global.Worker = worker_threads.Worker;
+  globalThis.Worker = worker_threads.Worker;
   var parentPort = worker_threads['parentPort'];
-  parentPort.on('message', (msg) => global.onmessage?.({ data: msg }));
-  Object.assign(globalThis, {
-    self: global,
-    postMessage: (msg) => parentPort['postMessage'](msg),
-  });
+  // 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);
+  }
 }
 #endif
 

src/runtime_common.js

@@ -38,12 +38,15 @@ var readyPromiseResolve, readyPromiseReject;
 #if (PTHREADS || WASM_WORKERS) && (ENVIRONMENT_MAY_BE_NODE && !WASM_ESM_INTEGRATION)
 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'];
-  parentPort.on('message', (msg) => global.onmessage?.({ data: msg }));
-  Object.assign(globalThis, {
-    self: global,
-    postMessage: (msg) => parentPort['postMessage'](msg),
-  });
+  // 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);
+  }
   // 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

test/codesize/test_codesize_minimal_pthreads.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 7694,
-  "a.out.js.gz": 3815,
+  "a.out.js": 7722,
+  "a.out.js.gz": 3812,
   "a.out.nodebug.wasm": 19604,
   "a.out.nodebug.wasm.gz": 9079,
-  "total": 27298,
-  "total_gz": 12894,
+  "total": 27326,
+  "total_gz": 12891,
   "sent": [
     "a (memory)",
     "b (emscripten_get_now)",

test/codesize/test_codesize_minimal_pthreads_memgrowth.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 8116,
-  "a.out.js.gz": 4015,
+  "a.out.js": 8145,
+  "a.out.js.gz": 4011,
   "a.out.nodebug.wasm": 19605,
   "a.out.nodebug.wasm.gz": 9080,
-  "total": 27721,
-  "total_gz": 13095,
+  "total": 27750,
+  "total_gz": 13091,
   "sent": [
     "a (memory)",
     "b (emscripten_get_now)",

test/common.py

@@ -390,6 +390,15 @@ def require_node(self):
     self.require_engine(nodejs)
     return nodejs
 
+  def get_node_test_version(self, nodejs):
+    override = os.environ.get('OVERRIDE_NODE_JS_TEST_VERSION')
+    if override:
+      override = override.removeprefix('v')
+      override = override.split('-')[0].split('.')
+      override = tuple(int(v) for v in override)
+      return override
+    return shared.get_node_version(nodejs)
+
   def node_is_canary(self, nodejs):
     return nodejs and nodejs[0] and ('canary' in nodejs[0] or 'nightly' in nodejs[0])
 
@@ -432,7 +441,7 @@ def try_require_node_version(self, major, minor = 0, revision = 0):
     nodejs = self.get_nodejs()
     if not nodejs:
       self.skipTest('Test requires nodejs to run')
-    version = shared.get_node_version(nodejs)
+    version = self.get_node_test_version(nodejs)
     if version < (major, minor, revision):
       return False
 
@@ -617,7 +626,7 @@ def setUp(self):
 
     nodejs = self.get_nodejs()
     if nodejs:
-      node_version = shared.get_node_version(nodejs)
+      node_version = self.get_node_test_version(nodejs)
       if node_version < (13, 0, 0):
         self.node_args.append('--unhandled-rejections=strict')
       elif node_version < (15, 0, 0):

test/test_other.py

@@ -12360,7 +12360,7 @@ def test_gen_struct_info(self):
     self.assertFileContents(path_from_root('src/struct_info_generated.json'), read_file('out.json'))
 
     # Same again for wasm64
-    node_version = shared.get_node_version(self.get_nodejs())
+    node_version = self.get_node_test_version(self.get_nodejs())
     if node_version and node_version >= (14, 0, 0):
       self.run_process([PYTHON, path_from_root('tools/gen_struct_info.py'), '--wasm64', '-o', 'out.json'])
       self.assertFileContents(path_from_root('src/struct_info_generated_wasm64.json'), read_file('out.json'))
@@ -12873,7 +12873,7 @@ def test_node_unhandled_rejection(self):
     self.build('main.c', cflags=['--pre-js=pre.js', '-sNODEJS_CATCH_REJECTION=0'])
     self.assertNotContained('unhandledRejection', read_file('main.js'))
 
-    if shared.get_node_version(self.get_nodejs())[0] >= 15:
+    if self.get_node_test_version(self.get_nodejs())[0] >= 15:
       self.skipTest('old behaviour of node JS cannot be tested on node v15 or above')
 
     output = self.run_js('main.js')
@@ -13952,7 +13952,7 @@ def test_parseTools_legacy(self):
 
   @requires_node
   def test_min_node_version(self):
-    node_version = shared.get_node_version(self.get_nodejs())
+    node_version = self.get_node_test_version(self.get_nodejs())
     node_version = '.'.join(str(x) for x in node_version)
     self.set_setting('MIN_NODE_VERSION', 300000)
     expected = 'This emscripten-generated code requires node v30.0.0 (detected v%s' % node_version