perf(treesitter): use child_containing_descendant() in has-ancestor? (#28512)

Problem: `has-ancestor?` is O(n²) for the depth of the tree since it iterates over each of the node's ancestors (bottom-up), and each ancestor takes O(n) time.
This happens because tree-sitter's nodes don't store their parent nodes, and the tree is searched (top-down) each time a new parent is requested.

Solution: Make use of new `ts_node_child_containing_descendant()` in tree-sitter v0.22.6 (which is now the minimum required version) to rewrite the `has-ancestor?` predicate in C to become O(n).

For a sample file, decreases the time taken by `has-ancestor?` from 360ms to 6ms.
This commit is contained in:
vanaigr
2024-05-16 09:57:58 -05:00
committed by GitHub
parent 31dc627969
commit 4b02916334
7 changed files with 129 additions and 27 deletions

View File

@@ -143,4 +143,30 @@ describe('treesitter node API', function()
eq(28, lua_eval('root:byte_length()'))
eq(3, lua_eval('child:byte_length()'))
end)
it('child_containing_descendant() works', function()
insert([[
int main() {
int x = 3;
}]])
exec_lua([[
tree = vim.treesitter.get_parser(0, "c"):parse()[1]
root = tree:root()
main = root:child(0)
body = main:child(2)
statement = body:child(1)
declarator = statement:child(1)
value = declarator:child(1)
]])
eq(lua_eval('main:type()'), lua_eval('root:child_containing_descendant(value):type()'))
eq(lua_eval('body:type()'), lua_eval('main:child_containing_descendant(value):type()'))
eq(lua_eval('statement:type()'), lua_eval('body:child_containing_descendant(value):type()'))
eq(
lua_eval('declarator:type()'),
lua_eval('statement:child_containing_descendant(value):type()')
)
eq(vim.NIL, lua_eval('declarator:child_containing_descendant(value)'))
end)
end)