module: fix leak of vm.SyntheticModule

Previously we maintain a strong persistent reference to the
ModuleWrap to retrieve the ID-to-ModuleWrap mapping from
the HostImportModuleDynamicallyCallback using the number ID
stored in the host-defined options. As a result the ModuleWrap
would be kept alive until the Environment is shut down, which
would be a leak for user code. With the new symbol-based
host-defined option we can just get the ModuleWrap from the
JS-land WeakMap so there's now no need to maintain this
strong reference. This would at least fix the leak for
vm.SyntheticModule. vm.SourceTextModule is still leaking
due to the strong persistent reference to the v8::Module.

src/module_wrap.cc

@@ -58,6 +58,7 @@ ModuleWrap::ModuleWrap(Environment* env,
   object->SetInternalField(kURLSlot, url);
   object->SetInternalField(kSyntheticEvaluationStepsSlot, undefined);
   object->SetInternalField(kContextObjectSlot, undefined);
+  MakeWeak();
 }
 
 ModuleWrap::~ModuleWrap() {

test/es-module/test-vm-synthetic-module-leak.js

@@ -0,0 +1,24 @@
+'use strict';
+
+// Flags: --experimental-vm-modules --max-heap-size=20
+// This tests that vm.SyntheticModule does not leak.
+// See https://github.com/nodejs/node/issues/44211
+
+require('../common');
+const vm = require('vm');
+
+let count = 0;
+async function createModule() {
+  const m = new vm.SyntheticModule(['bar'], () => {
+    m.setExport('bar', new Date().toISOString().repeat(1e6));
+  });
+  await m.link(() => {});
+  await m.evaluate();
+  count++;
+  if (count < 30000) {
+    setImmediate(createModule);
+  }
+  return m;
+}
+
+createModule();

test/known_issues/test-vm-source-text-module-leak.js

@@ -0,0 +1,37 @@
+'use strict';
+
+// This leaks because of the strong persistent v8::Module references
+// from ModuleWrap. We need replace that with a GC-aware ModuleWrap ->
+// v8::Module reference to fix this.
+// See: https://github.com/nodejs/node/issues/33439
+
+require('../common');
+const assert = require('assert');
+
+// We use a child process here because known_issues doesn't work with
+// hard crashes. We could just test this block with the flags when
+// it's fixed.
+if (process.argv[2] === 'child') {
+  const vm = require('vm');
+  let count = 0;
+  async function createModule() {
+    const m = new vm.SourceTextModule('export default "hello".repeat(1e5)');
+    await m.link(() => {});
+    await m.evaluate();
+    count++;
+    if (count < 30000) {
+      setImmediate(createModule);
+    }
+    return m;
+  }
+  createModule();
+} else {
+  const { spawnSync } = require('child_process');
+  const child = spawnSync(`${process.execPath}`, [
+    '--experimental-vm-modules',
+    '--max-heap-size=20',
+    __filename,
+    'child']
+  );
+  assert.strictEqual(child.status, null);
+}