1360605 - csscoverage report tool doesn't seem to work anymore

Status: RESOLVED WONTFIX

(DevTools :: Style Editor, enhancement)

Description

[Jeff Muizelaar [:jrmuizel]]

I'm not able to get this tool to work on any pages.

Comment 1

[Patrick Brosset <:pbro>]

I think csscoverage bugs should belong to the style editor component. That's where its UI is displayed and that's where it makes sense.

Comment 2

[Patrick Brosset <:pbro>]

In triage meeting today, we decided to close this bug as WONTFIX. Unfortunately we don't have the capacity to work on this tool now, and when code coverage tooling will become a priority for us again, it will most probably be done differently.
I don't think we should keep it open and accept patches either because the Style Editor's future is to be rewritten, so this would be a loss of time.

Comment 3

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

If it doesn't work, should it be removed then?  Isn't a broken but available thing worse than nothing at all?

Comment 4

[Patrick Brosset <:pbro>]

(In reply to J. Ryan Stinnett [:jryans] (use ni?) from comment #3)
> If it doesn't work, should it be removed then?  Isn't a broken but available
> thing worse than nothing at all?
That's true, although the nature of csscoverage made that a really minor problem so far: it's a GCLI command plus it's hidden by default.
But keeping it is probably useless nevertheless.
The only reason I'm hesitant for removing this command is that we've discussed about removing GCLI as a whole, and removing single commands might actually be more work if we're going to do this anyway. But we haven't taken this decision since we're waiting on more telemetry data.

Comment 5

[Markus Stange [:mstange]]

This feature is extremely useful for creating reduced testcases, which helps with fixing other bugs. I would really appreciate having it work again.
Fixing this might be considered a loss of time, but not being able to create reduced testcases is a loss of time as well.

Comment 6

[Patrick Brosset <:pbro>]

(In reply to Markus Stange [:mstange] from comment #5)
> This feature is extremely useful for creating reduced testcases, which helps
> with fixing other bugs. I would really appreciate having it work again.
> Fixing this might be considered a loss of time, but not being able to create
> reduced testcases is a loss of time as well.

Hey Markus, do you mind describing a little bit how you use the csscoverage tool to create reduced test cases? I definitely agree that easily being able to create these test cases is a big boost in productivity, but I'd just like to know how the csscoverage tool made that possible for you.
Maybe there's a tool that would be even better suited for this?

Comment 7

[Markus Stange [:mstange]]

Sure!

The bugs that I usually look into don't require JavaScript to appear, only HTML and CSS. They're usually some kind of painting bug, or an invalidation bug where we repaint too much during scrolling, for example.

Here's how I usually reduce websites to testcases:
 1. Save the website that shows the bug using File -> Save Page As... [Web Page, complete].
 2. Open the locally saved page in the browser and verify the problem still appears.
 3. In my editor, remove all <script> elements, if possible.
 4. Remove as many HTML elements as I can while the problem still appears. I usually try to do some kind of bisection, but sometimes it's a bit tricky because you need to preserve correct HTML element nesting.
 5. Once the HTML is as small as I can make it, I try to reduce the amount of CSS. At this point the page usually has many <link> elements and a few <style> elements that pull in CSS in some form or another.
For this, I run "csscoverage start", "csscoverage stop", and "csscoverage report".
This gives me a <style> element that only contains CSS code that is actually used by the HTML elements that are left over.
Now I put that <style> element into my page and remove all other stylesheets.
 6. Now I do another pass to trim down the CSS as much as possible.
 7. At the end I might do some more cleanup.
 8. Now I have a nice reduced testcase.

Steps 5 and 6 would take much longer if I wasn't able to let "csscoverage report" do most of the work.