1639648 - Support eagerly evaluating getters

Status: NEW

(DevTools :: Console, enhancement)

Description

[Jason Laster [:jlast]]

We currently show a button next to getters to evaluate them. It would be nice if we could first try to eagerly evaluate them so that we don't hide the value unnecessarily.

Comment 1

[Oriol Brufau [:Oriol]]

Something like Element.prototype.children can be eagerly evaluated, but if I inspect Element.prototype in the console, showing

TypeError: "'get children' called on an object that does not implement interface Element.

for every single getter will just be distracting IMO.

Comment 2

[Jason Laster [:jlast]]

diff --git a/devtools/server/actors/webconsole/eval-with-debugger.js b/devtools/server/actors/webconsole/eval-with-debugger.js
index 9d24ec2be8ef1..61a71d17451fb 100644
--- a/devtools/server/actors/webconsole/eval-with-debugger.js
+++ b/devtools/server/actors/webconsole/eval-with-debugger.js
@@ -53,6 +53,27 @@ function isObject(value) {
   return Object(value) === value;
 }

+exports.eagerlyEvaluateGetter = function({ value, frame, dbgWindow }) {
+  const noSideEffectDebugger = makeSideeffectFreeDebugger();
+
+  let result;
+  try {
+    const global = Cu.getGlobalForObject(value);
+    const dbgGlobal = noSideEffectDebugger.makeGlobalObjectReference(global);
+    const dbgObject = dbgGlobal.makeDebuggeeValue(value);
+    result = dbgObject.apply(frame);
+  } finally {
+    // We need to be absolutely sure that the sideeffect-free debugger's
+    // debuggees are removed because otherwise we risk them terminating
+    // execution of later code in the case of unexpected exceptions.
+    if (noSideEffectDebugger) {
+      noSideEffectDebugger.removeAllDebuggees();
+    }
+  }
+
+  return result;
+};
+

Comment 3

[Jason Laster [:jlast]]

I agree. we should not show errors.

Comment 4

[mattheww]

Attachment: Bug 1639648 - Eagerly evaluate getters

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee is inactive on Bugzilla, so the assignee is being reset.

Comment 6

[Suhaib Mujahid [:suhaib]]

Sorry, there was a problem with the detection of inactive users. I'm reverting the change.