[Precondition]
Make sure "devtools.netmonitor.features.serverSentEvents" is set to 'true'

[Affected Platforms]
All

[Affected Versions]
Firefox Nightly 82.0a1
Firefox Beta 81.0b8
Firefox Release 80.0.1

[Steps To Reproduce]

1. Open Firefox
2. Navigate to: https://farooqar.github.io/sse-echo/
3. Open the Devtools Panel
4. Select the "Network" tab (reload page if prompted)
5. Click "Connect!" on the page from Step 2
6. Select the new request from sse-echo.herokuapp.com and select the "Response" tab on the right side of the panel
7. Right-Click on the gray bar under "Filter Messages" and select a few columns which show different information about the messages (Size/Event Name)
8. Select another request from the Netmonitor and then select the request from sse-echo.herokuapp.com once again

[Expected Results]
The columns that were added to the information bar in Step 7 are not reset

[Actual Results]
The columns that were added to the information bar previously are reset

[Note]
This issue was introduced back when the Netmonitor still had a "Messages" tab and then it was transferred to the "Response" tab

Mozregression points to:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=dce1235761197e2ecf7ed03a42bb1e873e8c6261&tochange=eb67a3b38a01e30d90010c4b77e7e7cf48b5c8ac

Thanks for reporting!
I can reproduce the issue.

Thanks for reporting! Seems to be happening in case of websockets as well.

Hi Farooq! Yes, it's broken for both SSE an WS.
Do you know what could be wrong here?

Honza

Yes, the columns state is being reset to default here:
https://searchfox.org/mozilla-central/source/devtools/client/netmonitor/src/reducers/messages.js#105

I think we'll need to maintain two different states: sseColumns and wsColumns and update them here accordingly (Additionally, switch to correct columns state ['ws' or 'sse'] on channel change) :
https://searchfox.org/mozilla-central/source/devtools/client/netmonitor/src/reducers/messages.js#221

Thanks for the analysis Farooq! Any chance you could provide a patch for this? ;-)
Honza

I'll try to work on it by this weekend as soon as I get a little free (hopefully) :)

Farooq, this is almost done, just the test is missing. It would be great to land it.
Do you need any help?

Honza

Sorry Honza, I was just a little caught up in other stuff. I've updated the revision with the test.

https://hg.mozilla.org/mozilla-central/rev/ed0beb71ebca

Verified fixed on Nightly 83.0a1 (20201005215809)

Comment on attachment 9176825 [details]
Bug 1664185 - Persist selected columns for SSE / Websocket Events in the Response panel. r=honza

Beta/Release Uplift Approval Request

• User impact if declined: Columns customization (for WebSocket and ServerSideEvents inspection) not properly persisted.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Only affects web developers and only those who use the Network panel to inspect WS and/or SSE. Also rather smaller patch including automated test.
• String changes made/needed:

Comment on attachment 9176825 [details]
Bug 1664185 - Persist selected columns for SSE / Websocket Events in the Response panel. r=honza

sorry, we're on the last beta for 82 and this has been around for a while, so I'd rather let it ride the trains.