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 <expr> node under which the corresponding <SYMBOL_FUNCTION_CALL> node is found directly. depth = 0L means expr is matched directly to the SYMBOL_FUNCTION_CALL; depth > 1L means depth total <expr> 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"