Bug 159696 – Uncaught Exception: TypeError: null is not an object (evaluating 'this._contentViewContainer.currentContentView.showsFilterBar')

• Component: Web Inspector
• Status: RESOLVED FIXED

[Joseph Pecoraro]

Summary:
Uncaught exception closing Timeline Tab while viewing Script & Events Timeline.

Steps to Reproduce:
1. Inspect this page
2. Show timeline tab
3. Enable Scripts + Events timeline
4. Reload => populate timeline data
5. Select Script + Events timeline
6. Close Timeline Tab
  => Uncaught exception

Uncaught Exceptions:
 - TypeError: null is not an object (evaluating 'this._contentViewContainer.currentContentView.showsFilterBar') (at ScriptClusterTimelineView.js:65:80)
    showsFilterBar @ ScriptClusterTimelineView.js:65:80
    _updateFilterBar @ TimelineRecordingContentView.js:800:102
    _contentViewSelectionPathComponentDidChange @ TimelineRecordingContentView.js:325:30
    dispatch @ Object.js:162:30
    dispatchEventToListeners @ Object.js:177:21
    _currentContentViewDidChange @ ClusterContentView.js:225:38
    dispatch @ Object.js:162:30
    dispatchEventToListeners @ Object.js:169:17
    closeAllContentViews @ ContentViewContainer.js:345:38
    closed @ ClusterContentView.js:75:56
    _disassociateFromContentView @ ContentViewContainer.js:476:27
    closeAllContentViews @ ContentViewContainer.js:339:46
    closed @ TimelineRecordingContentView.js:198:79
    _disassociateFromContentView @ ContentViewContainer.js:476:27
    closeAllContentViews @ ContentViewContainer.js:339:46
    closed @ ContentBrowserTabContentView.js:121:71
    closed @ TimelineTabContentView.js:298:21
    _disassociateFromContentView @ ContentViewContainer.js:476:27
    closeContentView @ ContentViewContainer.js:309:46
    _tabBarItemRemoved @ TabBrowser.js:238:52
    dispatch @ Object.js:162:30
    dispatchEventToListeners @ Object.js:169:17
    removeTabBarItem @ TabBar.js:298:38
    _handleClick @ TabBar.js:607:34
    _handleClick @ [native code]

[Radar WebKit Bug Importer]

<rdar://problem/27312356>

[Matt Baker]

By the time ScriptClusterTimelineView showFilterBar is called, currentContentView has been destroyed. Simply adding a null check fixes this, but just kicks the can down the road:

[Error] Assertion Failed: Record selected in hidden overview graph – null
	selectRecord (TimelineOverview.js:399)
	_contentViewSelectionPathComponentDidChange (TimelineRecordingContentView.js:338)
	dispatch (Object.js:162)
	dispatchEventToListeners (Object.js:177)
	_currentContentViewDidChange (ClusterContentView.js:225)
	dispatch (Object.js:162)
	dispatchEventToListeners (Object.js:169)
	closeAllContentViews (ContentViewContainer.js:345)
	closed (ClusterContentView.js:75)
	_disassociateFromContentView (ContentViewContainer.js:476)
	closeAllContentViews (ContentViewContainer.js:339)
	closed (TimelineRecordingContentView.js:198)
	_disassociateFromContentView (ContentViewContainer.js:476)
	closeAllContentViews (ContentViewContainer.js:339)
	closed (ContentBrowserTabContentView.js:121)
	closed (TimelineTabContentView.js:298)
	_disassociateFromContentView (ContentViewContainer.js:476)
	closeContentView (ContentViewContainer.js:309)
	_tabBarItemRemoved (TabBrowser.js:238)
	dispatch (Object.js:162)
	dispatchEventToListeners (Object.js:169)
	removeTabBarItem (TabBar.js:234)
	_handleClick (TabBar.js:607)
	_handleClick

Working on a solution which addresses both.

[Joseph Pecoraro]

Well, probably _all_ of these forwarding messages should be resilient.

[Matt Baker]

(In reply to comment #3)
> Well, probably _all_ of these forwarding messages should be resilient.

This is a separate but related issue. Both problems stem from TimelineRecordingContentView handling SelectedPathComponentsDidChange, which is emitted by ContentViewContainer.closeAllContentViews().

If ContentView had a "closed" property we could early return from the SelectedPathComponentsDidChange handle. Luckily we can use the "visible" property in the same way. Skipping these updates when the tab is hidden should be safe, since TimelineRecordingContentView.shown() triggers a CurrentContentViewDidChange -> SelectedPathComponentsDidChange.

[Matt Baker]

Created attachment 283579 [details]
[Patch] Proposed Fix

[Joseph Pecoraro]

Comment on attachment 283579 [details]
[Patch] Proposed Fix

View in context: https://bugs.webkit.org/attachment.cgi?id=283579&action=review

r=me

> Source/WebInspectorUI/UserInterface/Views/TimelineRecordingContentView.js:322
> -        if (event.target !== this._timelineContentBrowser.currentContentView)
> +        if (!this.visible || event.target !== this._timelineContentBrowser.currentContentView)

Style: This would read better as a separate if + bail. These are two very different conditions.

[Matt Baker]

Created attachment 283581 [details]
[Patch] For Landing

[WebKit Commit Bot]

Comment on attachment 283581 [details]
[Patch] For Landing

Clearing flags on attachment: 283581

Committed r203198: <http://trac.webkit.org/changeset/203198>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.