Allow EditorManager to Open with Selection before Attachment

[colin-grant-work]

Signed-off-by: Colin Grant [email protected]

What it does

This PR fixes #8955 by interposing EditorManager.revealSelection between the creation of an editor widget and its attachment / opening. Previously, an editor would be attached, either independently or as part of an EditorPreviewWidget, and then revealSelection would be called. As a consequence, EditorManager.onCurrentEditorChangedEmitter was fired when the editor was picked up by the shell, before revealSelection had been called, and the top of the file would always be added to the navigation stack. With this PR, revealSelection can be called before the widget is picked up by the shell.

Alternative solutions to the problem include:

1. Rigging an event to fire when revealSelection is run and making the navigation system respond by removing the top of the relevant file from the top of the navigation stack. (Works pretty well)
2. Preventing the EditorManager from firing the onCurrentEditorChanged event for a widget that hasn't been opened yet. (Haven't tried, EditorPreviews - the most problematic case - do eventually call open.)
3. Any others you think would be cleaner than this modification of the get(OrCreate)ByUri mechanism.

How to test

1. Open a workspace with files in a language that provides definitions (e.g. TS files in the Theia repository)
2. Find reference to something defined in another file.
3. ctrl/cmd+click through to the definition.
4. Activate the command palette and select Go back
5. Observe that you navigate back the first file, without an intermediate stop at the start of the second file.

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

[vince-fugnitto]

There is some syntax errors (missing semicolon) which failed the build.
We may want to rebase the pull-request on master to resolve the issue with downloading the builtin extensions.

[vince-fugnitto]

@colin-grant-work looks like there is two different Colin authors :)

[colin-grant-work]

@colin-grant-work looks like there is two different Colin authors :)

I keep trying to expunge the other one from the git history, but he's quite persistent! I'll make another attempt...

[colin-grant-work]

I believe the ghost has been banished, and the code seems to be up to date, despite a slow pipeline between my fork and this PR.

[vince-fugnitto]

@colin-grant-work the changes look good to me, and they fix the described issue 👍