Because tables are matrices and not really trees, the tree differ can show odd results for more complex operations, for example cell 'A' merged with 'E' below:
Description
Description
Details
Details
Related Changes in Gerrit:
| Subject | Author | Repo | Branch | Lines +/- | |
|---|---|---|---|---|---|
| Daff table diffing | Tchanders | VisualEditor/VisualEditor | master | +11 K -139 |
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Open | None | T211897 Visual Diffs: Improve table diffing | |||
| Open | None | T149851 Handle visual diffing of table cell merges |
Event Timeline
Comment Actions
In general though this problem seems like potentially a lot of work for an uncommon edge case.
Comment Actions
Another example is a row/col deletion that results a colspan/rowspan change:
Here 7,8,10 is deleted which makes 9 shorter:
The output is still more legible than wikitext though.
Comment Actions
-> 
We also need to decide how we'd like table (un)merges to appear.
Unmergres can simple be shown as the insertion of all but the top left cell:
Going the other way is a little more complex, to be discussed?
Comment Actions
Agree on un-merges. Not sure what you're showing in "the other way" – is that adding things to an already merged cell?
Comment Actions
It shows merging 4 cells (in red) into 1 cell (green). The easier solution is just to not show the removed content.
Comment Actions
Change 455321 had a related patch set uploaded (by Esanders; author: Tchanders):
[VisualEditor/VisualEditor@master] Daff table diffing
Comment Actions
| Before patch | After patch | Comments | |
| A+E merge |  |  | Layout less broken visually, but the removed content is not shown |
| Merge |  |  | As above |
| Unmerge |  |  | Almost no change |
| Row removal |  |  | Both quite broken. Displaying removed cells will always cause problems when colspan/rowspan is involved |
I think not showing the remove content in cell merges is better than breaking the layout, and we can iterate towards the design shown above: