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Hamza
ab7b584811
A form past the pass's depth limit is removed rather than walked. That
is the fail-safe choice for a redaction -- marked content inside a form
we cannot read would otherwise survive -- but it also removes whatever
else that form drew, marked or not. At a limit of 12, a page with a
13-deep chain lost the text of its innermost form with nothing in it
marked.
Measured on a page that draws HEAD, a chain of forms whose innermost
draws DEEP, then TAIL, with only HEAD marked:
chain before after (12) after (50)
1 HEAD DEEP TAIL DEEP TAIL DEEP TAIL
12 HEAD DEEP TAIL DEEP TAIL DEEP TAIL
13 HEAD DEEP TAIL TAIL DEEP TAIL
14 HEAD DEEP TAIL TAIL DEEP TAIL
50 HEAD DEEP TAIL TAIL DEEP TAIL
51 HEAD TAIL TAIL TAIL
The limit is now 50, which is what the renderer follows
(MAX_NESTED_INTERPRETATION_DEPTH) and what Edit text's reader follows
(text::MAX_FORM_DEPTH). So anything a reader can see, this pass can
walk. The last row is why 50 and not more: at 51 the renderer does not
draw DEEP either, so removing that form costs nothing visible and the
fail-safe still holds.
Fixes #3645's data loss. The other half of that report -- that nothing
tells the user when a form is removed -- is untouched: Report.forms_removed
is counted but the engine's edit pipeline does not carry it out, and the
one channel that reaches the result (doc.edit_notices) is typed
TextNotice, for text that could not be drawn. Widening that type or
adding a channel is a design choice for the maintainers rather than
something to slip into this fix.