Determine the code context of each pattern occurrence

Assigns every pattern found by find_patterns() the code context it would execute in.

Usage

determine_code_contexts(tree, patterns, rules)

Arguments

tree

The xml_document parse tree for one script (from parse_code()).

patterns

Data frame from find_patterns(), carrying its matched nodes in the "nodes" attribute aligned to the rows.

rules

Loaded rules; only rules$code_contexts (columns name, xpath) is used.

Value

patterns with an added code_context column – a named context, "top_level" or "in_function", never NA. The "nodes" attribute is dropped from the result.

Details

A pattern occurs in a named context iff its node is a descendant of that context's node; where it sits inside more than one, the innermost wins. Containment is tested by exact XML path identity, never by path-prefix comparison, since sibling paths such as expr[1] and expr[12] would false-match.

"top_level" and "in_function" are not rule-matched. They are computed here for a pattern in no named context: "in_function" when it has a function-definition ancestor, "top_level" when it does not.