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XPath Predicate: Not Guarded by a Sibling Call

Source: R/ast.R
not_under_fn_with_call_xpath.Rd

Returns an XPath predicate that restricts matches to nodes whose innermost enclosing function body does not also contain a call to any of funs. This is how a check enforces a guard, for instance that an options() call is paired with an on.exit() in the same function.

Usage

not_under_fn_with_call_xpath(funs)

Arguments

funs

Character vector of guard function names (e.g. "on.exit").

Value

A single character string: an XPath predicate to splice into a query after a node test.

Details

The predicate anchors on ancestor::expr[FUNCTION][1], the nearest function definition, and searches its whole subtree. Anchoring on the innermost function keeps it correct where the guard belongs to an inner function rather than an outer one, and covers a call sitting in a default argument as well as one in the body.

See also

xpath_lints().

Examples

predicate <- not_under_fn_with_call_xpath(c("on.exit", "local_options"))
paste0("//SYMBOL_FUNCTION_CALL[text() = 'options'][", predicate, "]")
#> [1] "//SYMBOL_FUNCTION_CALL[text() = 'options'][not(ancestor::expr[FUNCTION][1]//SYMBOL_FUNCTION_CALL[text() = 'on.exit' or text() = 'local_options'])]"