Support formatting of all cells in notebook

[DonJayamanne]

Currently we have support for formatting individual cells
However formatting entire document does not seem to work (VSC Has a specific command for this)

Note: black supports ipynb out of the box

See #1187 (comment)

[nickeubank]

For what it's worth, I'm not actually sure this is feasible -- notebook cells are often run and written out of sequence, and I'm not sure if a formatter like black would be able to parse out-of-execution-order cells effectively, could it? I think a better solutions might be #7058

[MarcoGorelli]

For what it's worth, I'm not actually sure this is feasible -- notebook cells are often run and written out of sequence, and I'm not sure if a formatter like black would be able to parse out-of-execution-order cells effectively, could it? I think a better solutions might be #7058

Not sure I see what the issue is, but black's current way of running Jupyter Notebooks doesn't require cells to have been executed in order

[nickeubank]

Oh great! Right, I guess black doesn't care about syntax stuff like running undefined vars. Nevermind!

[jucor]

@DonJayamanne as workaround, since two months ago black supports formating .ipynb files :)