Bug 117755 – Web Inspector: Infrequent uncaught exception with debugger popovers breaks inspector

• Status: RESOLVED
• Resolution: FIXED
• Component: Web Inspector

[Joseph Pecoraro]

I've been able to somewhat reliably reproduce an uncaught exception with debugger popovers:

    [Error] TypeError: 'undefined' is not a function (evaluating 'bestFrame.minX()')
	_update (Popover.js, line 228)
	present (Popover.js, line 117)
	_showPopover (SourceCodeTextEditor.js, line 982)
	_showPopoverForUndefined (SourceCodeTextEditor.js, line 1089)
	populate (SourceCodeTextEditor.js, line 952)
	populate
	dispatch (InspectorBackend.js, line 209)
	dispatchNextQueuedMessageFromBackend (Main.js, line 290)
	(anonymous function)

I threw in some logging and caught what was happening:

    // Logging: console.log("FRAME", JSON.stringify(bestFrame), typeof bestFrame.minX);
    [Log] FRAME {"origin":{"x":427,"y":235},"size":{"width":83,"height":51}} function (Popover.js, line 229, x3)
    [Log] FRAME {"origin":{"x":427,"y":67},"size":{"width":83,"height":51}} function (Popover.js, line 229, x10)
    [Log] FRAME {"origin":{"x":0,"y":0},"size":{"width":0,"height":0}} undefined (Popover.js, line 229)
    // ERROR

Because WebInspector.Rect.ZERO_RECT was constructed before we replace the WebInspector.Rect.prototype it didn't get the methods we expected it to have!

    js> WebInspector.Rect.ZERO_RECT instanceof WebInspector.Rect
    false

[Radar WebKit Bug Importer]

<rdar://problem/14194615>

[Joseph Pecoraro]

Doing a quick search through the code base, ZERO_SIZE and ZERO_RECT were the only 2 objects being initialized before we reassigned the prototype. There were only a few other objects, all safe.

    shell> ack '^WebInsp.*?= new'
    Geometry.js
    87:WebInspector.Size.ZERO_SIZE = new WebInspector.Size(0, 0);
    178:WebInspector.Rect.ZERO_RECT = new WebInspector.Rect(0, 0, 0, 0);

    Object.js
    235:WebInspector.notifications = new WebInspector.Object;

    Popover.js
    56:WebInspector.Popover.AnchorSize = new WebInspector.Size(22, 11);
    57:WebInspector.Popover.ShadowEdgeInsets = new WebInspector.EdgeInsets(WebInspector.Popover.ShadowPadding);

[Radar WebKit Bug Importer]

<rdar://problem/14194674>

[Joseph Pecoraro]

Also the only non-WebInspector namespaced object (InspectorBackend) was correct.

[Joseph Pecoraro]

Created attachment 204948 [details]
[PATCH] Proposed Fix

[WebKit Commit Bot]

Comment on attachment 204948 [details]
[PATCH] Proposed Fix

Clearing flags on attachment: 204948

Committed r151704: <http://trac.webkit.org/changeset/151704>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.