Cached expressions don't need to be transformed with transformers in
parse_transform_serialize_r_block(), we simply return text for the
top-level token.
shallowify(pd)Expressions that are cached are already styled correctly. We can make the
parse table shallow at these locations, fully relying on the text column:
remove all children, as they are not needed anymore.
mark the expression as a terminal.
Note that we do not cache top-level comments. Because package code has a lot
of roxygen comments and each of them is a top-level expression, checking is
very expensive. More expensive than styling, because comments are always
terminals. This will also yield large speed improvements in
compute_parse_data_nested() because nesting is expensive and will not be
done for cached expressions.
Because the structure of the parse table is not always "top-level expression first, then children", this function creates a temporary parse table that has this property and then extract the ids and subset the original parse table so it is shallow in the right places.