apply topological sort to reorder cells in editor

[tmchartrand]

Description

In many cases, I add a cell out of its topological order simply for convenience when editing (ie working with a later portion of the notebook and realize a needed variable was not defined). In this case the work would be more polished for a reader if the cells were reordered to match the topological order (as is currently done when exporting).

Suggested solution

Add a UI command that reorders cells in their topological order.
Also consider a cell-level command that moves that cell only to immediately above the first dependent cell.

Alternative

This can currently be done manually.

Additional context

No response

[akshayka]

Sounds like a reasonable request. How would you handle things like mo.md(), which might float to the top or coalesce together?

[tmchartrand]

I guess I haven't looked in detail at how the current topological sort does it, but I would suggest looking for the minimal reordering compatible with the topological constraints (in some loose sense anyway, not sure if this is well-defined) , so cells not on the dependency tree just wouldn't move.

[tmchartrand]

Ah, I see ties are currently broken by registration order - seems reasonable, but for this application it would be preferable to use the current layout order for that I think.

[mscolnick]

I could be thinking about layout order wrong, but in my interpretation, that would for sure bubble up markdown to the top. Maybe there is some algorithm/ruleset that would be agreeable (like sorting between pure-markdown blocks, but i can still think of edge cases).

[tmchartrand]

Oh yes of course, they'll always be clumped if the use of existing order is just to break ties.
I guess it makes more sense in my initial framing, a minimal reordering compatible with the topological constraints (maybe just a simple insertion sort following the dependency tree). Then the markdown cells would remain in place.