node-find: Find node(s) matching a pattern

In astgrepr: Parse and Manipulate R Code

Find node(s) matching a pattern

Description

Those functions find one or several nodes based on some rule:

• node_find() returns the first node that is found;

• node_find_all() returns a list of all nodes found.

Some arguments (such as kind) require some knowledge of the tree-sitter grammar of R. This grammar can be found here: https://github.com/r-lib/tree-sitter-r/blob/main/src/grammar.json.

Usage

node_find(x, ..., files = NULL)

node_find_all(x, ..., files = NULL)

Arguments

x	A node, either from tree_root() or from another ⁠node_*()⁠ function.
...	Any number of rules created with ast_rule().
files	A vector of filenames containing rules. Those must be .yaml files.

Value

node_find() returns a single SgNode.

node_find_all() returns a list of SgNodes.

Examples

src <- "x <- rnorm(100, mean = 2)
    any(duplicated(y))
    plot(mtcars)
    any(duplicated(x))"

root <- src |>
  tree_new() |>
  tree_root()

root |>
  node_find(ast_rule(pattern = "any(duplicated($A))"))

root |>
  node_find_all(ast_rule(pattern = "any(duplicated($A))"))

# using the 'kind' of the nodes to find elements
src <- "
  a <- 1
  while (TRUE) { print('a') }
"

root <- src |>
  tree_new() |>
  tree_root()

root |>
  node_find(ast_rule(kind = "while_statement"))

# one can pass several rules at once
src <- "x <- rnorm(100, mean = 2)
    any(duplicated(y))
    plot(mtcars)
    any(duplicated(x))
    while (TRUE) { print('a') }"
root <- src |>
  tree_new() |>
  tree_root()

root |>
  node_find(
    ast_rule(pattern = "any(duplicated($A))"),
    ast_rule(kind = "while_statement")
  )

root |>
  node_find_all(
    ast_rule(pattern = "any(duplicated($A))"),
    ast_rule(kind = "while_statement")
  )

astgrepr documentation built on June 8, 2025, 11:05 a.m.