Multi-client remote debugging support

[4eveRS]

Describe the solution you'd like
Since version 63, Chrome supports multi-client remote debugging, which means it can handle multiple debugger clients (such as webContents.debugger and devTools) at the same time.

In Electron current version, v3.0 Beta, this functionality is not working properly. Once the user set the debbuger in a webContent, if the same webContent request to open the devTools, the previous debugger attached to the webContent is detached and all configurations are lost.

I think many Electron users will find this functionality very useful, since it can give the full support of chrome devTool in app background while the app users can access the devTools of the same webContent.

My application for example, which is a browser, really needs that functionality in order to analyze the page and it's content, while it can't / shouldn't block the user to access the devTools of that same page.

Additional context

https://developers.google.com/web/updates/2017/10/devtools-release-notes#multi-client
https://crbug.com/129539

[MarshallOfSound]

We actually have a test to ensure this works, see

electron/spec/node-spec.js

Line 244 in 39c5c20

assert.equal(secondSessionOpened, true)

Can you fill out the Bug Report issue template in a comment below, in particular a minimal repro and version information would be very useful

[4eveRS]

Electron version: v3.0.0-beta.5
Operating System: macOS Sierra 10.12.6

Expected Behavior
Multi-client remote debugging should be supported by Electron.

Actual Behavior
Multi-client remote debugging is not actually supported.

Example of actual behavior
Create a webview and attach a debugger to its webContents.
Send commands to test if its working.
Enable webview devTools.
webContents debugger is detached and lose all commands sent before the devTools was opened.

To Reproduce

https://gist.github.com/4eveRS/b80a836c313864d394191e7347efa580

$ git clone git@gist.github.com:b80a836c313864d394191e7347efa580.git
$ npm install
$ npm start || electron .

[4eveRS]

One thing that I just noticed is that, if we use commands that use debugger/devTools interface, for example, setting a viewport in a webview through webContents.enableDeviceEmulation(), if later we set a debugger to that same webContents, that device emulation is disabled.

So there's a issue when running debuggers, devTools and commands in webContents that utilize the devTools protocol.

[deepak1556]

@4eveRS Thanks for the test case, i have fixed the multi client problem while doing a cleanup in #14522, will backport the specific fix to 3-0-x branch soon.

[deepak1556]

Fixed in #14566

[praneetrohida]

I'm having the exact same issue in Electron 8.x

To elaborate, if I have the devtools open for a webview and if I call webContents.debugger.attach() for that webview, the devtools lose connection with the page.