util: optimize promise introspection

bnoordhuis · rvagg · commit d8ab4e185dc9 · 2015-10-02T13:39:24.000+10:00
Use V8's builtin ObjectIsPromise() to check that the value is a promise before creating the promise mirror. Reduces garbage collector strain in the (common) non-promise case, which is beneficial when inspecting deep object graphs. PR-URL: #3130 Reviewed-By: Evan Lucas <evanlucas@me.com> Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
diff --git a/lib/util.js b/lib/util.js
@@ -3,7 +3,9 @@
 const uv = process.binding('uv');
 const Buffer = require('buffer').Buffer;
 const internalUtil = require('internal/util');
+
 var Debug;
+var ObjectIsPromise;
 
 const formatRegExp = /%[sdj%]/g;
 exports.format = function(f) {
@@ -183,11 +185,21 @@ function getConstructorOf(obj) {
 }
 
 
+function ensureDebugIsInitialized() {
+ if (Debug === undefined) {
+ const runInDebugContext = require('vm').runInDebugContext;
+ const result = runInDebugContext('[Debug, ObjectIsPromise]');
+ Debug = result[0];
+ ObjectIsPromise = result[1];
+ }
+}
+
+
 function inspectPromise(p) {
- Debug = Debug || require('vm').runInDebugContext('Debug');
- var mirror = Debug.MakeMirror(p, true);
- if (!mirror.isPromise())
+ ensureDebugIsInitialized();
+ if (!ObjectIsPromise(p))
 return null;
+ const mirror = Debug.MakeMirror(p, true);
 return {status: mirror.status(), value: mirror.promiseValue().value_};
 }
 

-Original file line number
+Diff line change
 constuv=process.binding('uv');
 constBuffer=require('buffer').Buffer;
 constinternalUtil=require('internal/util');
++
 varDebug;
 +varObjectIsPromise;
 constformatRegExp=/%[sdj%]/g;
 exports.format=function(f){
+}
 +functionensureDebugIsInitialized(){
 +if(Debug===undefined){
 +construnInDebugContext=require('vm').runInDebugContext;
 +constresult=runInDebugContext('[Debug, ObjectIsPromise]');
 +Debug=result[0];
 +ObjectIsPromise=result[1];
 +}
 +}
++
++
 functioninspectPromise(p){
 -Debug=Debug||require('vm').runInDebugContext('Debug');
 -varmirror=Debug.MakeMirror(p,true);
 -if(!mirror.isPromise())
 +ensureDebugIsInitialized();
 +if(!ObjectIsPromise(p))
 returnnull;
 +constmirror=Debug.MakeMirror(p,true);
 return{status: mirror.status(),value: mirror.promiseValue().value_};
+}