DevTools/Features/Debugger

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Status

Debugger
Stage	Development
Status	In progress
Release target	`
Health	OK
Status note	JSD2 backend interface has landed, work ongoing on the remote debugging server and the user interface

{{#set:Feature name=Debugger

|Feature stage=Development |Feature status=In progress |Feature version=` |Feature health=OK |Feature status note=JSD2 backend interface has landed, work ongoing on the remote debugging server and the user interface }}

Team

Product manager	Kevin Dangoor
Directly Responsible Individual	Dave Camp
Lead engineer	Panos Astithas
Security lead	`
Privacy lead	`
Localization lead	`
Accessibility lead	`
QA lead	`
UX lead	`
Product marketing lead	`
Operations lead	`
Additional members	Jason Orendorff, Jim Blandy, Victor Porof

{{#set:Feature product manager=Kevin Dangoor

|Feature feature manager=Dave Camp |Feature lead engineer=Panos Astithas |Feature security lead=` |Feature privacy lead=` |Feature localization lead=` |Feature accessibility lead=` |Feature qa lead=` |Feature ux lead=` |Feature product marketing lead=` |Feature operations lead=` |Feature additional members=Jason Orendorff, Jim Blandy, Victor Porof }}

Open issues/risks

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Stage 1: Definition

1. Feature overview

New JavaScript debugger.

2. Users & use cases

JavaScript developers

3. Dependencies

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4. Requirements

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Non-goals

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Stage 2: Design

5. Functional specification

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6. User experience design

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Stage 3: Planning

7. Implementation plan

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8. Reviews

Security review

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Privacy review

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Localization review

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Accessibility

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Quality Assurance review

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Operations review

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Stage 4: Development

9. Implementation

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Stage 5: Release

10. Landing criteria

` {{#set:Feature open issues and risks=` |Feature overview=New JavaScript debugger. |Feature users and use cases=JavaScript developers |Feature dependencies=` |Feature requirements=` |Feature non-goals=` |Feature functional spec=` |Feature ux design=` |Feature implementation plan=` |Feature security review=` |Feature privacy review=` |Feature localization review=` |Feature accessibility review=` |Feature qa review=` |Feature operations review=` |Feature implementation notes=` |Feature landing criteria=` }}

Feature details

Priority	P2
Rank	2
Theme / Goal	`
Roadmap	Developer Tools
Secondary roadmap	`
Feature list	Desktop
Project	`
Engineering team	DevTools

{{#set:Feature priority=P2

|Feature rank=2 |Feature theme=` |Feature roadmap=Developer Tools |Feature secondary roadmap=` |Feature list=Desktop |Feature project=` |Feature engineering team=DevTools }}

Team status notes

	status	notes
Products	`	`
Engineering	`	`
Security	sec-review-needed	`
Privacy	`	`
Localization	`	`
Accessibility	`	`
Quality assurance	`	`
User experience	`	`
Product marketing	`	`
Operations	`	`

{{#set:Feature products status=`

|Feature products notes=` |Feature engineering status=` |Feature engineering notes=` |Feature security status=sec-review-needed |Feature security health=` |Feature security notes=` |Feature privacy status=` |Feature privacy notes=` |Feature localization status=` |Feature localization notes=` |Feature accessibility status=` |Feature accessibility notes=` |Feature qa status=` |Feature qa notes=` |Feature ux status=` |Feature ux notes=` |Feature product marketing status=` |Feature product marketing notes=` |Feature operations status=` |Feature operations notes=` }}

Designs

• JSInspector
• Remote_Debugging_Protocol
• DevTools/Features/Debugger/Notes has further implementation notes.

Planning

What follows is some plan-related sketching, please update appropriately. List of milestones/sprints is roughly in order.

Bootstrapping/Stack Traces

• Working remote protocol, exposing stack frames with JSD2.
• Relying on debugger statement, no breakpoints.
• Only "continue" after stopping in debugger.
• UI shell in firefox
• UI for stack traces (without arguments)
• No iframe support just yet.

Description	Area	Bug	Owner	Best	Likely	Worst	Status
Debugging global/Root actor registration/Socket Listener	Remote Proto		dcamp	2d	3d	5d	In remote-debug.
Browser root actor/tab actors (not as thread-like actors)	Browser Proto		dcamp	2d	2d	4d	In remote-debug.
Protocol handler thread (socket transport)	Remote Proto		dcamp	?	?	?	Put off for now.
Debug Object creation and debuggerHook	JSD2		jorendorff	1d	1d	2d	In jsdb2
Debug Object loader	JSD2ish		dcamp				In remote-debug
Debug Object support for frame inspection	JSD2		jorendorff				type, this, older, live, callee, generator, arguments complete.
Debug Object support for the toplevel globals in tab actor - debuggerHook spawning a nested event loop.	Browser Proto		dcamp	2d	2d	4d	In remote-debug
New execution model specification in the remote protocol	Remote Proto		jimb				Complete
debuggerHook and "continue" exposed over remote protocol as specified.	Remote Proto		dcamp	3d	3d	5d	In remote-debug.
Client JS API (socket transport)	UI Shell		dcamp	1d	2d	3d	In remote-debug.
HTML UI shell per tab, in its own window	UI Shell		dcamp	2d	2d	5d	In remote-debug
UI responding to pauses (from debugger keyword)	Execution Handling		dcamp	2d	2d	4d	In remote-debug
HTML Stack frame viewer (no locals/environment yet, just	Execution Handling		dcamp	2d	3d	5d	In patch queue

Property Viewer

• A simple property viewer, limited to viewing frame arguments for now.

Description	Area	Bug	Owner	Best	Likely	Worst	Status
Debug.Object.prototype.{proto, class, isFunction, name, getOwnPropertyDescriptor, getOwnPropertyNames}	JSD2		jorendorff/jimb
Primitive data grips for frame arguments	Remote Proto		dcamp	1d	1d	2d	In remote-debug
Pause-lifetime object grips	Remote Proto		dcamp	1d	1d	2d	In remote-debug
Thread-lifetime grip promotion	Remote Proto		dcamp	1d	2d	4d	In remote-debug
Object grip enumeration	Remote Proto		dcamp	1d	2d	4d	Waiting on jsd2
Property UI design	UI		past/dcamp	1d	1d	2d
Property Inspector UI	UI		past	?	?	?	Split up as needed.

Source Viewer

• Enough to visualize current line/stack frames/etc.
  • Debug.Script.prototype.{url,startLine,length,getAllOffsets,getLineOffsets,getOffsetLine} - jorendorff
  • Debug.Frame.prototype.{callee,script,offset} - jorendorff
• No source list yet, will only reflect sources handed to it in pause states.
• Can use normal view source/firebug method (loading from necko preferring the cache) for getting static script sources (in-document <script> etc).
• Needs the engine to provide sources for exotic script sources (eval/appendNode/etc.)
• Very simple source viewer, improving the source viewer can happen outside the critical path.

Execution

• throw hook (Debug.hooks.throw) - jorendorff - Done.
• error hook (Debug.hooks.error) - jorendorff
• resume (resumption values) - jorendorff - Done.
• work out low-level stepping support with the JM team - jorendorff/jimb
• implement Debug object stepping support (Debug.hooks.interrupt, Debug.Script.prototype.singleStepMode, etc.) - jorendorff
• step into/step out/finish - dcamp

In this timeframe, we also want to be able to:

• Show native calls on the stack - jorendorff, luke
• Show debugger frames on the stack - jorendorff

Frame Tree Support

• Debug.prototype.{add,remove}Debuggee() - jorendorff
• Frame tree support in the tab actors.

Environment/Property Viewer

• JSD2 support
  • Debug.Frame.prototype.environment - jorendorff
  • Debug.Environment.prototype.{type,outerEnvironment,object, boundIdentifiers,getVariableDescriptor,findBinding} - jorendorff

By the time this milestone is complete, we'll have a somewhat competent debugger if you're willing to use debugger; statements instead of breakpoints.

Source Selector

• JSD2 support
  • newScript hook
  • enumerate scripts? Maybe not - since we need currently need to reload anyway to recompile scripts for debugging, might be ok to always just watch the newScript hook.
• Protocol support
  • new script notification.

• UI support: dropdown of available scripts, triggering loads in the source viewer.

Breakpoints

• JSD2 support.
• Protocol-side breakpoints will set physical breakpoints at each script (including newly-added scripts)
• Need to work out breakpoint persistence across reloads (needs to be done early enough to catch scripts run during the load).
• Set breakpoints in the source gutter
• Set breakpoints from a command line (?)
• Disable/Enable/Delete breakpoints

More Milestones

In no particular order...

• Web Worker debugging (might not be needed for an initial release, but would be really nice)
• Chrome debugging (probably not be needed for an initial release)

Floating Tasks

Here are a few tasks that I haven't slotted into any specific milestone, and could be tackled separately alongside the other milestones. At least some of these would block a final release of a capable debugger.

Description	Area	Bug	Owner	Best	Likely	Worst	Status
E10S content process support	Remote Proto		dcamp?	1w	3w	2w
Improved script origin information	JSD2	bug 637572	jimb
Waive slow script dialog (jorendorff was seeing them after resuming)	JSD2
Improve source viewer (after basic source viewer is added)	Firefox UI		No Owner