I suppose I’ll copy/paste my comments on the PR here, too for visibility
I generally like the magic command approach and I see why it is appealing.
One thing that might give everyone some comfort is fastpages versions are pinned to specific versions of nbdev. So if this is eventually merged, it will not break fastpages unless people upgrade to a new version . In that case, I suppose we could make a conversion script that automatically executes upon an upgrade ( we can trigger this automatically if it is detected that someone is upgrading from version < 2.x to version > 3.x). That way we could mitigate the effect of any breaking changes.
TLDR; If we want to continue working on this, I think a conversion script to convert all notebooks to use magic commands is necessary to automatically mitigate breaking changes.
Let me know if anyone has any thoughts about this, in theory, a conversion script doesn’t seem like it would be that complicated.