deleting a dependency of a cell causes 'Failed to load URL'

[jaked]

instead it should cause an error about an undefined variable (when you delete the cell defining the variable).

I think maybe we aren't cleaning up the mapping of exported variables to cells?

[jaked]

I can't reproduce this as described.

If I delete a depended-on cell, I get a ReferenceError (correct behavior).

If I delete the contents of the depended-on cell, or rename the depended-on variable, I don't get a ReferenceError, but the variable value is undefined. If I manually reexecute the depending cell then I get a ReferenceError.

[jaked]

I think what's happening here is that we rewrite cells to import their dependencies, so e.g. if I have cells

const x = 7

and

x + x

then the second one is rewritten to

import { x } from [the first cell]

x + x

Now if you change the first cell (delete its contents or rename x), the second doesn't get rewritten, but importing the now-nonexistent variable returns undefined instead of throwing ReferenceError.

I think the right fix is to rewrite cells in light of current bindings when they are invalidated.