async_hooks: use scope for defaultTriggerAsyncId

Previously the getter would mutate the kDefaultTriggerAsncId value. This
refactor changes the setter to bind the current kDefaultTriggerAsncId to
a scope, such that the getter doesn't have to mutate its own value.

PR-URL: https://github.com/nodejs/node/pull/17273
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 12 insertions, 9 deletions

diff --git a/lib/internal/async_hooks.js b/lib/internal/async_hooks.js
index 2cd4137fd08..4bd5f3191b6 100644
--- a/lib/internal/async_hooks.js
+++ b/lib/internal/async_hooks.js
@@ -250,9 +250,6 @@ function newUid() {
 // constructor is complete.
 function getDefaultTriggerAsyncId() {
   var defaultTriggerAsyncId = async_id_fields[kDefaultTriggerAsyncId];
-  // Reset value after it's been called so the next constructor doesn't
-  // inherit it by accident.
-  async_id_fields[kDefaultTriggerAsyncId] = -1;
   // If defaultTriggerAsyncId isn't set, use the executionAsyncId
   if (defaultTriggerAsyncId < 0)
     defaultTriggerAsyncId = async_id_fields[kExecutionAsyncId];
@@ -260,10 +257,20 @@ function getDefaultTriggerAsyncId() {
 }
 
 
-function setDefaultTriggerAsyncId(triggerAsyncId) {
+function defaultTriggerAsyncIdScope(triggerAsyncId, opaque, block) {
   // CHECK(Number.isSafeInteger(triggerAsyncId))
   // CHECK(triggerAsyncId > 0)
+  const oldDefaultTriggerAsyncId = async_id_fields[kDefaultTriggerAsyncId];
   async_id_fields[kDefaultTriggerAsyncId] = triggerAsyncId;
+
+  var ret;
+  try {
+    ret = Reflect.apply(block, null, opaque);
+  } finally {
+    async_id_fields[kDefaultTriggerAsyncId] = oldDefaultTriggerAsyncId;
+  }
+
+  return ret;
 }
 
 
@@ -285,10 +292,6 @@ function emitInitScript(asyncId, type, triggerAsyncId, resource) {
   // manually means that the embedder must have used getDefaultTriggerAsyncId().
   if (triggerAsyncId === null) {
     triggerAsyncId = getDefaultTriggerAsyncId();
-  } else {
-    // If a triggerAsyncId was passed, any kDefaultTriggerAsyncId still must be
-    // null'd.
-    async_id_fields[kDefaultTriggerAsyncId] = -1;
   }
 
   emitInitNative(asyncId, type, triggerAsyncId, resource);
@@ -341,7 +344,7 @@ module.exports = {
   // Internal Embedder API
   newUid,
   getDefaultTriggerAsyncId,
-  setDefaultTriggerAsyncId,
+  defaultTriggerAsyncIdScope,
   emitInit: emitInitScript,
   emitBefore: emitBeforeScript,
   emitAfter: emitAfterScript,