ToC Run Cells doesn't run nested cells after non-header markdown cells

[andrewfulton9]

Description

If I try to run code cells under a ToC header with the run cells command, the cells below a non-header markdown cell will not be run.

Notice in the above screen shot that when I use run cells on the "Text" header, the code cell below the header, defining and printing text is not run. This is because of the markdown cell immediately before it. However when I use run cells on the "HTML" header, the cells below do run because there are no non-header markdown cells between them and their section header.

Reproduce

create a notebook with three cells. The first cell make a markdown header, the second cell make a markdown cell and fill with text without any markdown headers. the 3rd cell, fill with python code.

1. From the ToC, right click on header
2. click "Run Cell(s)"
3. notice the third code cell is not run

Expected behavior

I would expect any code cells nested under a header to be run when I use the Run Cells command

Context

• Operating System and version: Linux Ubuntu 18.04
• Browser and version: Chrome 97.0.4692.99
• JupyterLab version: master

[andrewfulton9]

@meeseeksdev tag "pkg:toc"