Build the call tree of a function

call_stack() takes the name of a function, optionally namespaced (e.g. "dplyr::select"), statically parses its body, and recursively resolves every function it calls, building a tree of those calls, the calls those functions make, and so on.

Resolution is static (read from the function's source code), not a runtime trace: the function is never called. UseMethod() dispatch is resolved by looking up the generic's registered S3 methods and following each one. Other dynamic calls (NextMethod(), S4 and R6 dispatch, non-standard evaluation) show as leaves rather than being followed further.

Usage

call_stack(fn, max_depth = Inf)

Arguments

fn

Character string naming a function, e.g. "dplyr::select", "pkg:::internal_fun", or "mean".

max_depth

Maximum recursion depth. Default Inf, which follows every call down to a primitive or a cycle already visited.

Value

An object of class call_stack: a named list with name (the function name) and calls (a list of child nodes with the same shape).

See also

print.call_stack() for how the tree is drawn.

Examples

call_stack("mean.default", max_depth = 1)
#> █─mean.default
#> ├─.Internal
#> ├─anyNA
#> ├─c
#> ├─floor
#> ├─is.complex
#> ├─is.logical
#> ├─is.na
#> ├─is.numeric
#> ├─isTRUE
#> ├─length
#> ├─return
#> ├─sort.int
#> ├─stop
#> ├─unique
#> └─warning

# a generic: UseMethod() is replaced by the methods it dispatches to
call_stack("mean", max_depth = 1)
#> █─mean
#> ├─mean.Date
#> ├─mean.POSIXct
#> ├─mean.POSIXlt
#> ├─mean.default
#> ├─mean.difftime
#> ├─mean.quosure
#> └─mean.vctrs_vctr