Fix hover tooltip not updated after character deletions

[yamaton]

References

Fixes #866

Code changes

Changed EditorAdapter to emit update signals when nontrivial change.removed exists.

User-facing changes

None.

Backwards-incompatible changes

My concern is that the original behavior might have been intentional as was in the comment.

// deletion - ignore

If so, this PR may affect other signal receivers.

Chores

• linted
• tested
• documented
• changelog entry

[github-actions]

👈 Launch a binder notebook on branch yamaton/jupyterlab-lsp/fix-uncleared-hover-cache

[yamaton]

FYI: I could reproduce the CI error about jupyter serverextension list in the following minimum environment.

mamba create -c conda-forge -n py37-minimum-test python=3.7 jupyterlab=3.3 jupyter_server
conda activate py37-minimum-test 
jupyter serverextension list

[krassowski]

My concern is that the original behavior might have been intentional as was in the comment.

I think that the original intent was to avoid triggering completer on deletion, but indeed this is not where this should be handled. I think it is fine to change it - let's give it a try.