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perf(treesitter): use child_containing_descendant() in is_ancestor()

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**Problem:** `is_ancestor()` uses a slow, bottom-up parent lookup which
has performance pitfalls detailed in #28512.

**Solution:** Take `is_ancestor()` from $O(n^2)$ to $O(n)$ by
incorporating the use of the `child_containing_descendant()` function
This commit is contained in:
Riley Bruins 2024-09-25 11:33:14 -07:00 committed by Christian Clason
parent 921dc22fc0
commit 64847fbdc9
2 changed files with 8 additions and 12 deletions
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12
runtime/lua/vim/treesitter.lua
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@ -159,16 +159,8 @@ function M.is_ancestor(dest, source)
return false return false
end end
local current = source ---@type TSNode? -- child_containing_descendant returns nil if dest is a direct parent
while current ~= nil do return source:parent() == dest or dest:child_containing_descendant(source) ~= nil
if current == dest then
return true
end
current = current:parent()
end
return false
end end
--- Returns the node's range or an unpacked range table --- Returns the node's range or an unpacked range table

8
test/functional/treesitter/utils_spec.lua
View File

@ -21,12 +21,16 @@ describe('treesitter utils', function()
local parser = vim.treesitter.get_parser(0, 'c') local parser = vim.treesitter.get_parser(0, 'c')
local tree = parser:parse()[1] local tree = parser:parse()[1]
local root = tree:root() local root = tree:root()
_G.ancestor = root:child(0) _G.ancestor = assert(root:child(0))
_G.child = _G.ancestor:child(0) _G.child = assert(_G.ancestor:named_child(1))
_G.child_sibling = assert(_G.ancestor:named_child(2))
_G.grandchild = assert(_G.child:named_child(0))
end) end)
eq(true, exec_lua('return vim.treesitter.is_ancestor(_G.ancestor, _G.child)')) eq(true, exec_lua('return vim.treesitter.is_ancestor(_G.ancestor, _G.child)'))
eq(true, exec_lua('return vim.treesitter.is_ancestor(_G.ancestor, _G.grandchild)'))
eq(false, exec_lua('return vim.treesitter.is_ancestor(_G.child, _G.ancestor)')) eq(false, exec_lua('return vim.treesitter.is_ancestor(_G.child, _G.ancestor)'))
eq(false, exec_lua('return vim.treesitter.is_ancestor(_G.child, _G.child_sibling)'))
end) end)
it('can detect if a position is contained in a node', function() it('can detect if a position is contained in a node', function()