1251757 - Unable to break via source maps

Status: RESOLVED FIXED

(DevTools :: Debugger, defect, P2)

Description

[Yury Delendik (:yury)]

STR:
1. open devtools debugger tab (check "Show Original Sources" option)
2. open http://people.mozilla.org/~ydelendik/tmp/dbgwast/t.html
3. select "labels.wast" source code
4. set breakpoint at line 12
5. refresh

Actual result:
Debugger stops but it does not show where is stops, no locals are visible

Expected result:
Debugger stops and let code to be stepped

Comment 1

[Eddy Bruel [:ejpbruel]]

It looks like the breakpoint you're setting is in top-level code that is executed immediately on refresh.

This is a difficult problem. We need to load the source map before we set any breakpoints, or the breakpoints won't end up where you expect. We need to set the breakpoints before the script starts executing, or control will have already passed through the point where the breakpoint was supposed to be set. However, we also don't really want to wait for the source map to be loaded before the script starts executing, since that will hang the UI.

I'd like for this to be fixed, but fixing it properly will require us to rethink some parts of the design of the debugger. That makes this a medium term project, so I'm going to flag this as P2.

Comment 2

[Tom Tromey :tromey]

This seems to work for me now.
Yury, would you mind giving it a try as well?

Comment 3

[Bryan Clark (DevTools PM) [:clarkbw]]

Attachment: Screen Shot 2017-05-19 at 8.37.11 AM.png

Seems to work for me.  However the __locals object is empty and I'm not sure if that's correct.

Comment 4

[Yury Delendik (:yury)]

The test case at people.mozilla.org is lost, I'm unable to confirm the fix. Closing based on comment 2 and comment 3.