[Bug] Desynchronization after delete cell

[jim-portegies]

What happened?

If a code cell is deleted in an input area and this is reverted with Ctrl + Z, in the underlying text document, the text is not reinserted, while in the editor it is, leading to desynchronization.

How can we reproduce this issue?

Example:

1. Open the Waterproof tutorial.
2. Write We conclude that (3 = 3). in the first exercise.
3. Open the text version of the waterproof tutorial to the side.
4. While the cursor is in the input area, select "Parent" and hit "Delete".
5. Undo the deletion using ctrl-z.
6. Observe that the input area does have content in the editor, but does not have content in the underlying text file
7. For instance selecting the text We conclude that (3 = 3). and then hitting backspace will result in a skull.

What was supposed to happen?

The text should also reappear in the underlying file.

[DikieDick]

Edited to include step 5.

[DikieDick]

This seems to be an error in the way we handle ProseMirror's ReplaceStep.

The ReplaceStep that is generated by ProseMirror after the undo does contain the text inside of the code cell. However, in the mapping we don't generate a correct change for this, that we eventually send to VSCode.

The ReplaceStep in question is nested, i.e., it contains content for:

1. Input area
2. Coq block
3. Code cell
4. Text

[DikieDick]

@XyntaxCS is it possible to add support for steps with 'nested' content in the new mapping?

[DikieDick]

Will be addressed in #30