1468603 - --jsdebugger does not halt on "debugger;" statements in content frame scripts

Status: NEW

(DevTools :: General, defect, P3)

Description

[Andreas Tolfsen ❲:ato❳]

The Browser Toolbox Debugger for chrome is opened and halts on "debugger;" statements when Firefox is launched with the --jsdebugger flag.  Having the ability to set breakpoints like this in your file is an immensely powerful debugging technique, as it is not always possible to coordinate adding breakpoints by hand when starting Firefox or when Firefox is under automation.

It is however not possible to make the debugger halt when setting breakpoints in content frame scripts.  Whilst it is my understanding that it _is_ possible to debug frame scripts by changing the debugger context by selecting the targetted document in the right-hand corner of the UI, the debugger does not _automatically_ open and break on "debugger;" statements in frame scripts.

Comment 1

[Jason Laster [:jlast]]

CC Honza, could you look into this?

Comment 2

[Jan Honza Odvarko [:Honza] (always need-info? me)]

(In reply to Andreas Tolfsen ⦗:ato⦘ from comment #0)

The Browser Toolbox Debugger for chrome is opened and halts on "debugger;"
statements when Firefox is launched with the --jsdebugger flag. Having the
ability to set breakpoints like this in your file is an immensely powerful
debugging technique, as it is not always possible to coordinate adding
breakpoints by hand when starting Firefox or when Firefox is under
automation.

Correct, this works well.

It is however not possible to make the debugger halt when setting
breakpoints in content frame scripts. Whilst it is my understanding that it
is possible to debug frame scripts by changing the debugger context by
selecting the targetted document in the right-hand corner of the UI, the
debugger does not automatically open and break on "debugger;" statements
in frame scripts.

I am not sure if I understand this part.

Is the following STR describing what you have in mind?

STR:

1. Open http://janodvarko.cz/tests/bugzilla/1468603/ (it should break in an content iframe when you reload the page with content debugger opened)
2. Close Firefox and change the settings so the page is opened on startup
3. Append --jsdebugger to your command line
4. Run Firefox again
5. The debugger doesn't break in the iframe

So, it only breaks with the content Toolbox.

Honza

Comment 3

[Andreas Tolfsen ❲:ato❳]

I think I may not have explained myself well enough in comment #0.

The concrete problem I have is that using a debugger; statement
in a frame script loaded by a system XPCOM component, does not
automatically break when you run it with the --jsdebugger flag.

An example:

1. Add debugger; somewhere in testing/marionette/listener.js,
   for example in registerSelf.

2. Run any Marionette test:

   % ./mach marionette-test --jsdebugger

3. Click the button in the dialogue that appears to have the tests
   run.

Perhaps there is something we’re not doing to instrument the
browser the right way for the content debugger to open?

Comment 4

[Henrik Skupin [:whimboo][⌚️UTC+2] (away July 24th - August 16th)]

Andreas, I can remember we discussed that with Mike Conley a long time ago during an all hands meeting. By that time he mentioned how to do that. But actually I cannot remember the/a bug where we documented that. :/

Maybe he can help again, and we finally document it.

Comment 5

[Mike Conley (:mconley) (:⚙️)]

The Browser Toolbox connects to and only notices scripts running in the parent process. Frame scripts running in the content process will not be noticed by it.

There's a secondary toolbox - the Browser Content Toolbox - which attaches to the currently selected tab's content process. This is what you want to open to see your breakpoint. You can find the Browser Content Toolbox menu item inside the Web Developer menu.

Unfortunately, I don't believe there's a command-line argument that allows you to open the Browser Content Toolbox - although that might be good to have (presumably connecting to the initial tab's content process).

Comment 6

[Andreas Tolfsen ❲:ato❳]

Right, I filed this bug after our conversation at an All Hands, and
I think it would be a powerful debugging technique to have
--jsdebugger also halt and open the correct debugger on debugger;
in content frame scripts. Do you agree that’s reasonable?

As I understand it, --jsdebugger sets these prefs:

• devtools.browsertoolbox.panel → jsdebugger
• devtools.debugger.remote-enabled → true
• devtools.chrome.enabled → true
• devtools.debugger.prompt-connection → false

So if I interpret your reply correctly, we’d need additional pref(s)
in DevTools to open the Browser Content Toolbox?

Comment 7

[Mike Conley (:mconley) (:⚙️)]

(In reply to Andreas Tolfsen ⦗:ato⦘ from comment #6)

So if I interpret your reply correctly, we’d need additional pref(s)
in DevTools to open the Browser Content Toolbox?

Yes, I think that's probably what you want here.

Comment 8

[Jason Laster [:jlast]]

Moving to devtools > general so that we can open the discussion to the larger devtools team.

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

The priority flag is not set for this bug.
:pbro, could you have a look please?

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