Get a child's field name by index

These functions return the field name for the ith child of x.

• node_field_name_for_child() considers both named and anonymous children.

• node_field_name_for_named_child() considers only named children.

Nodes themselves don't know their own field names, because they don't know if they are fields or not. You must have access to their parents to query their field names.

Usage

node_field_name_for_child(x, i)

node_field_name_for_named_child(x, i)

Arguments

x

[tree_sitter_node]

A node.

i

[integer(1)]

The index of the child to get the field name for.

Value

The field name for the ith child of x, or NA_character_ if that child doesn't exist.

Examples

language <- treesitter.r::language()
parser <- parser(language)

text <- "fn <- function() { 1 + 1 }"
tree <- parser_parse(parser, text)
node <- tree_root_node(tree)

# Navigate to first child
node <- node_child(node, 1)
node
#> <tree_sitter_node>
#> 
#> ── Text ───────────────────────────────────────────────────────────────
#> fn <- function() { 1 + 1 }
#> 
#> ── S-Expression ───────────────────────────────────────────────────────
#> (binary_operator [(0, 0), (0, 26)]
#>   lhs: (identifier [(0, 0), (0, 2)])
#>   operator: "<-" [(0, 3), (0, 5)]
#>   rhs: (function_definition [(0, 6), (0, 26)]
#>     name: "function" [(0, 6), (0, 14)]
#>     parameters: (parameters [(0, 14), (0, 16)]
#>       open: "(" [(0, 14), (0, 15)]
#>       close: ")" [(0, 15), (0, 16)]
#>     )
#>     body: (braced_expression [(0, 17), (0, 26)]
#>       open: "{" [(0, 17), (0, 18)]
#>       body: (binary_operator [(0, 19), (0, 24)]
#>         lhs: (float [(0, 19), (0, 20)])
#>         operator: "+" [(0, 21), (0, 22)]
#>         rhs: (float [(0, 23), (0, 24)])
#>       )
#>       close: "}" [(0, 25), (0, 26)]
#>     )
#>   )
#> )

# Get the field name of the first few children (note that anonymous children
# are considered)
node_field_name_for_child(node, 1)
#> [1] "lhs"
node_field_name_for_child(node, 2)
#> [1] "operator"

# Get the field name of the first few named children (note that anonymous
# children are not considered)
node_field_name_for_named_child(node, 1)
#> [1] "lhs"
node_field_name_for_named_child(node, 2)
#> [1] "rhs"

# 10th child doesn't exist, this returns `NA_character_`
node_field_name_for_child(node, 10)
#> [1] NA