Improvements for integration with track changes

[scofalik]

Suggested merge commit message (convention)

Feature: TableWalker will now return cell value also for spanned cells when traversing a table with includeSpanned option set to true. Additionally, isSpanned property was introduced in returned values.
Internal: Improvements in table plugin allowing for integration with track changes.

BREAKING CHANGE: TableWalker will not return undefined as cell value for spanned cells anymore. Use isSpanned instead.

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Additional information

Requires ckeditor/ckeditor5-engine#1781

[jodator]

I'm not happy with the change of yielding spanned cells. We loose the information when using includeSpanned: true that currently yielded value is spanned by other cell.

So the idea before inlcudeSpanned: true was to yield every table cell location (not a table cell). So if table should be 3x3 cells and have some cells merged (spanned over others) then it would have for instance 6 child table cells instead of 9.

Iterating over table in normal mode would yield 6 values while using includeSpanned: true should yield all 9 locations from which 3 would be not have a table cell but will be spanned by others.

It's not ideal API and probably confusing one. We can rename the options to make it clearer. Also I would keep the information about the "spanned" cell. Previously it was cell: undefiend but we can make this explicit as isSpanned: true or cell: undefined, spannedBy: cell. There is a possibility that the logic of other command would simplify by that.

[scofalik]

As far as includeSpanned and cell value. (I think) I understand the intention behind includeSpanned and it worked fine but in my case, I needed to get to the cell that is spanning over given table location. For example, when I was iterating over all locations in a column, I wanted to get both cells that "starts" in that column (those were added to a suggestion for sure) but also I wanted to store spanned cells because they might need to be added to a suggestion too (upon further processing).

I've checked if changing cell from undefined breaks anything and it didn't (so no scripts depended on undefined value). So, for me, not passing a value there is wasting an information that we have for free. I am fine for adding isSpanned though, for theoretical future needs.

[jodator]

I am fine for adding isSpanned though, for theoretical future needs.

So let's do this - we shouldn't loose that information. Also update the commit message regarding this change.

[jodator]

Just one question we're OK.

[scofalik]

Okay, I updated docs and fixed what we agreed on fixing.

[jodator]

Waits for: ckeditor/ckeditor5-engine#1781.