Make accesses to Error.stack property lazy
This significantly improves the performance on browsers
that does lazy stack evaluation (e.g. Chrome).
Change-Id: I7cf41abf3078e71f549198ebcc9e3fe1a66e533d
diff --git a/user/src/com/google/gwt/core/client/impl/StackTraceCreator.java b/user/src/com/google/gwt/core/client/impl/StackTraceCreator.java
index 02a0a2c..f755e9a 100644
--- a/user/src/com/google/gwt/core/client/impl/StackTraceCreator.java
+++ b/user/src/com/google/gwt/core/client/impl/StackTraceCreator.java
@@ -170,9 +170,17 @@
@Override
public native void collect(Object t, Object jsThrown) /*-{
- // TODO(goktug): optimize for Chrome by not evaluating stack (use Error.captureStackTrace)
- t.stack = (jsThrown && jsThrown.stack) || @StackTraceCreator::makeException()().stack;
- }-*/;
+ // Carefully crafted to delay the 'stack' property until stack trace construction as it is
+ // very costly in some browsers (e.g. Chrome).
+
+ var referenceThrown = jsThrown instanceof Object && "stack" in jsThrown
+ ? jsThrown
+ : @StackTraceCreator::makeException()();
+
+ @StackTraceCreator::addLazyProperty(*)(t, "stack", function() {
+ return referenceThrown.stack;
+ });
+ }-*/;
@Override
public StackTraceElement[] getStackTrace(Object t) {
@@ -378,6 +386,36 @@
return e.stack ? e.stack.split('\n') : [];
}-*/;
+ private static native void addLazyProperty(JavaScriptObject obj, String name,
+ JavaScriptObject getterFn) /*-{
+ if (Object.defineProperty) {
+ try {
+ Object.defineProperty(obj, name, {
+ configurable: true,
+ get: getterFn,
+ set: function(value) {
+ Object.defineProperty(this, name, {
+ value: value,
+ configurable: true,
+ writable: true,
+ });
+ },
+ });
+ } catch(defPropException) {
+ // This might happen because some old browsers like Safari5, IE8, have Object.defineProperty
+ // method which doesn't work on all objects.
+ };
+
+ // At this point we need to be sure that the property added, if not should fallback to eager.
+ if (name in obj) {
+ return;
+ }
+ }
+
+ // Fallback to eager property
+ obj[name] = getterFn();
+ }-*/;
+
private static native <T> T splice(T arr, int length) /*-{
(arr.length >= length) && arr.splice(0, length);
return arr;
