Bug 28665 – Inspector: Throws an Error on "null"

• Component: Web Inspector (Deprecated)
• Status: RESOLVED FIXED

[Joseph Pecoraro]

The Console is throwing an error on "null".  This seems to happen because after the result of an eval goes to InspectorController.wrapObject(), which doesn't handle null very well.

Current Behavior:

> null
TypeError: Result of expression 'wrapper' [null] is not an object.
> [null, null]
[]
> var o = { a: null }
Object
  a: null
> o.a
TypeError: Result of expression 'wrapper' [null] is not an object.


Expected Behavior (from Safari 4.0.3):

> null
null
> [null, null]
[null, null]
> var o = { a:null }
undefined
> o
Object
  a: null
> o.a
null

[Joseph Pecoraro]

Created attachment 38447 [details]
[PATCH] One Possible Solution

No other falsey value causes wrapObject() to return a null value (NaN, undefined, 0, '').  This solution tackles null before calling wrapObject.  Another solution could be checking the result of wrapObject (wrapper).  And yet another solution could handle null differently inside InspectorController.wrapObject().  This approach seemed simplest.

Pavel, would there be a more appropriate solution?

[Joseph Pecoraro]

Actually that "exception: false" part isn't necessary, because thats the implicit default if its left out.  So I can remove that if this is an okay way to go.

[Pavel Feldman]

> +            return { value: InjectedScript.createProxyObject(null, null), exception: false };

We don't wrap primitive values with proxy objects at the moment, why wrapping null. I would just do

    return { value: null };

However, that would require fixing ConsoleView's proxy detection:

    var isProxy = typeof output === "object";

should be replaced with

    var isProxy = output !== null && typeof output === "object";

[Pavel Feldman]

Additional note: fixing InspectorController.wrapObject would be nicer, but you would need to do that in both bindings (comparing to null are returning argument). It will still require mentioned fix in the console though.

[Joseph Pecoraro]

Created attachment 38453 [details]
[PATCH] Pavel's JavaScript Approach

[Joseph Pecoraro]

(In reply to comment #4)
> Additional note: fixing InspectorController.wrapObject would be nicer, but you
> would need to do that in both bindings (comparing to null are returning
> argument). It will still require mentioned fix in the console though.

What I said earlier was not accurate.  wrapObject doesn't have trouble with null, it just ends up returning the value passed in, which was null, and a null value isn't handled well afterwards.  I like this approach.

[Eric Seidel (no email)]

Comment on attachment 38453 [details]
[PATCH] Pavel's JavaScript Approach

Clearing flags on attachment: 38453

Committed r47696: <http://trac.webkit.org/changeset/47696>

[Eric Seidel (no email)]

All reviewed patches have been landed.  Closing bug.