Fix search highlights removal on clearing input box

[krassowski]

References

Fixes #15688

Code changes

• add integration test
• add unit test
• fix the problem by ending search when input query is empty

User-facing changes

Clearing search box clears active search.

Before	After

Backwards-incompatible changes

None

[jupyterlab-probot]

Thanks for making a pull request to jupyterlab!
To try out this branch on binder, follow this link:

[krassowski]

Note: the only failing test (Notebook scrolls to heading) is unrelated #15670.

[krassowski]

@JasonWeill would you be willing to review this PR and #15703 which we could include in a small 4.0.x release?

[JasonWeill]

@krassowski I checked out this branch and I ran the following commands in a fresh Conda environment with all Apple Silicon-related dependencies already installed:

pip install -e ".[dev,test]"
jlpm install
jlpm run build  # Build the dev mode assets (optional)

After running jupyter lab, I opened a notebook with one cell, a Markdown cell with "Now is the time for all good men to come to the aid of their country":

I then opened the search box and searched for Now, which worked as expected:

When I backspace to N, the search highlights are correct, case insensitively:

… but then when I backspace over N, the search continues to highlight all instances of N, until I dismiss the search box:

[krassowski]

After running jupyter lab, I opened a notebook with one cell,

Thank you for testing it @JasonWeill. Do you see the red strip dev mode indicator at the top of the page? If not it is likely that you are served production assets from older version - can you try shutting jupyterlab and starting again with jupyter lab --dev-mode?

[JasonWeill]

@krassowski Thank you! I relaunched in dev mode and things look good. Should be good to merge once UI tests are updated (if necessary).

[krassowski]

@meeseeksdev please backport to 4.0.x