HTML report filter not working properly

[RichardsonWTR]

Describe the bug The filter on the coverage resets its state when I go to the previous page.

To Reproduce Python 3.8.10
coverage.py v7.0.1 in my code, and the live example as linked below in the v7.4.0

1. Go to the example page, as indicated here:
2. See the number of lines, 10 lines (counting the "total").
3. Type something in the filter on the top right end of the page, e.g., utils. The results will be filtered and there are now only 4 lines (counting the "total").
4. Click in a file, e.g., cogapp/utils.py
5. Go back to the previous page (click ALT + left)
6. See that the text is still on the filter, on the top right of the page, but the results is not filtered.

Expected behavior When I go back to the previous page, the results must be filtered.

Additional context

When the code below runs, the filter text is still empty.

    // Trigger change event on setup, to force filter on page refresh
    // (filter value may still be present).
    document.getElementById("filter").dispatchEvent(new Event("input"));

Location

Hotfix

Whithout thinking too much, this is a solution that I came up with: appending a new keyboard event after a timeout period. It's not the ideal, but it's working.

This is my script to see the coverage results:

coverage html  && \
    echo 'window.addEventListener("load",(function(){setTimeout((function(){const t=document.getElementById("filter");t&&t.dispatchEvent(new Event("input"))}),5)}));' >> htmlcov/coverage_html.js && \
    xdg-open 'http://localhost:8000' && \
    python -m http.server -d htmlcov

[nedbat]

I so what you mean in Chrome. Firefox works as you expect. I'm sure there's something that can fix it well. Also, returning to the index page by clicking the ^ index link on the file page brings you to the index page with the filter empty and nothing filtered. It should also keep the filter I think.

[RichardsonWTR]

Well noted. In Firefox it works as expected. When I go to the previous page the results flash just like my hotfix solution, but it works. And yes, I detected this bug in Chrome.
Besides, I agree that clicking on ^ index should keep the filter.