Data loss: Custom editors do not properly deal with extension host restarts

[bpasero]

Steps to Reproduce:

1. install an extension that leverages custom editors (non-text based, like Luna paint or Hex editor)
2. open a folder
3. open a file in hex editor or luna paint
4. make the editor dirty
5. add a folder to the workspace
6. the extension host restarts
7. click on another editor
8. click back into the custom editor

=> the custom editor is gone and so is the data

[bpasero]

Unfortunately this can result in data loss as you can see from the video below:

[lramos15]

I can't reproduce this using luna paint.

[bpasero]

Here is how it reproduces for me with Luna paint running out of sources (auto save disabled):

[lramos15]

Hmm. Seems like a race condition, I follow those exact steps and still can't repro. I would be willing to investigate with you.

[bpasero]

The more I think about it, the more I feel we really should stop restarting extension hosts: #69335

[sbatten]

We must restart the extension host in the event the workspace is no longer trusted, so perhaps custom editors need to participate in that transition to avoid data loss