Find calls made through a function's name

Finds do.call("system", ...) and its siblings: a call to a function named by a string literal, which no pattern rule's XPath can see because the target is not a call site.

Usage

find_indirect(tree, pattern_rules, file_context)

Arguments

tree

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

pattern_rules

Data frame of pattern rules (rules$patterns from load_rules()). Only the functions column decides what is found; the matched rule supplies the row's rule, message, and attck.

file_context

Package-root-relative path, carried through for joining.

Value

A list with two data frames, shaped exactly as find_patterns() returns them so the two can be combined:

patterns

The columns find_patterns() produces, plus indirect, which is TRUE on every row. Carries the matched nodes as a "nodes" attribute, aligned to the rows.

errors

Data frame with columns step, file_context, rule, message.

Details

A finding is reported under the rule that owns the name, not under a rule of its own, so filtering for rule == "system" returns every call to system however it was spelled, and the indirect column says which is which. The line and column point at the string literal rather than at do.call, since the literal is what a reviewer needs to look at.

Security considerations

A name is claimed by a rule only if calling it bare would have matched that rule's own XPath, which inst/scripts/build_db.R verifies when the database is built. An indirect finding therefore can never be attributed to a rule that would not have reported the direct call.

A name the rules do not declare is not reported, so this under-covers rather than guesses – as does a target assembled at runtime, such as do.call(paste0("sys", "tem"), ...), which carries no literal to read.