Get the name of the function matched by an XPath

Often, it is more helpful to tailor the message of a lint to record which function was matched by the lint logic. This function encapsulates the logic to pull out the matched call in common situations.

Usage

xp_call_name(expr, depth = 1L, condition = NULL)

Arguments

expr: An xml_node or xml_nodeset, e.g. from xml2::xml_find_all().
depth: Integer, default 1L. How deep in the AST represented by expr should we look to find the call? By default, we assume expr is matched to an node under which the corresponding node is found directly. depth = 0L means expr is matched directly to the SYMBOL_FUNCTION_CALL; depth > 1L means depth total nodes must be traversed before finding the call.
condition: An additional (XPath condition on the SYMBOL_FUNCTION_CALL required for a match. The default (NULL) is no condition. See examples.

Examples

xml_from_code <- function(str) {
  xml2::read_xml(xmlparsedata::xml_parse_data(parse(text = str, keep.source = TRUE)))
}
xml <- xml_from_code("sum(1:10)")
xp_call_name(xml, depth = 2L)
#> [1] "sum"

xp_call_name(xml2::xml_find_first(xml, "expr"))
#> [1] "sum"

xml <- xml_from_code(c("sum(1:10)", "sd(1:10)"))
xp_call_name(xml, depth = 2L, condition = "text() = 'sum'")
#> [1] "sum"