Allow multiple editors for same file

[colin-grant-work]

What it does

This PR fixes #3857 by allowing multiple editors to be opened for the same URI.

The basic principle is that all widget creation calls that go through the EditorManager add a counter field to the widget options so that the widget manager creates separate widgets for separate counter entries. The get calls use an existing counter value; getOrCreate an old if available, a new if necessary; and openToSide always creates a new value to ensure that a new widget is created.

How to test

1. I've added a set of commands to split the view in various directions. Open an editor and run them. Each new editor should look like its parent: same visible range and selection.

• In VSCode only one copy of an editor widget can exist on the same tabbar. If you create a new instance to the side and then move it to its parent's tabbar, one of them will be closed. I haven't tried to replicate that functionality here, but if it seems desirable, I can.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

Signed-off-by: Colin Grant colin.grant@ericsson.com

[vince-fugnitto]

I verified the changes and they look really good 👍 we now support splitting the same editor URI multiple times.

Do we plan on supporting different editors in the pull-request, or do we keep it for subsequent updates? (for example diff-editors):

split-diff.mp4

[colin-grant-work]

Do we plan on supporting different editors in the pull-request, or do we keep it for subsequent updates? (for example diff-editors):

Happy to take a look at how other editors are initialized and try to accommodate them. I'll see about diff editors today - any other editor types you're interested in?

[vince-fugnitto]

Happy to take a look at how other editors are initialized and try to accommodate them. I'll see about diff editors today - any other editor types you're interested in?

I'm thinking anything which makes sense and is handled by editor-manager. For example, I tried with rendered previews (markdown) and it does not split which is correct. The diff is one example I am aware of.

[colin-grant-work]

Turns out I was just using a bad strategy to get the URI. I've replaced editorWidget.editor.getResourceUri() with just editorWidget.editor.uri, and that handles normal and diff editor directly.

[vince-fugnitto]

I verified the changes under multiple use-cases and it works very well:

• confirmed that we can successfully split editors (standard editors, diff).
• editor state is preserved on split.
• confirmed that the 'split' commands work successfully.
• confirmed that the two keybindings work successfully.
• confirmed the following use-cases work for day-to-day use:
  • search and replace with multiple duplicate editors.
  • decorations for duplicate editors.
  • problem markers for duplicate editors.