`ts_node_parent` can still return wrong parent for a zero-width node

[vanaigr]

Problem

Related to #3185.

Sorry if I misunderstood something in how tree-sitter works, but it looks like ts_node_parent() sometimes returns the previous sibling (or its descendant) of a zero-width node instead of its parent. This can happen when the previous sibling has children, since currently ts_node_parent() descends into the first node that has child nodes and can contain the given node:

https://github.com/tree-sitter/tree-sitter/blob/4d8b031bcc218977187575e22181106d48f82b86/lib/src/node.c#L523

I made a modified version of python grammar that could produce such a scenario (python.patch). It allows function definitions without ":" at the end, so that parameters node could be a sibling of a zero-width body.

Steps to reproduce

test.patch

```diff diff --git a/cli/src/tests/node_test.rs b/cli/src/tests/node_test.rs index 193b4562..d4c987db 100644 --- a/cli/src/tests/node_test.rs +++ b/cli/src/tests/node_test.rs @@ -250,7 +250,7 @@ fn test_node_parent_of_child_by_field_name() { #[test] fn test_parent_of_zero_width_node() { - let code = "def dupa(foo):"; + let code = "def dupa(foo)"; let mut parser = Parser::new(); parser.set_language(&get_language("python")).unwrap(); @@ -258,12 +258,13 @@ fn test_parent_of_zero_width_node() { let tree = parser.parse(code, None).unwrap(); let root = tree.root_node(); let function_definition = root.child(0).unwrap(); - let block = function_definition.child(4).unwrap(); + let block = function_definition.child(3).unwrap(); let block_parent = block.parent().unwrap(); assert_eq!(block.to_string(), "(block)"); - assert_eq!(block_parent.kind(), "function_definition"); - assert_eq!(block_parent.to_string(), "(function_definition name: (identifier) parameters: (parameters (identifier)) body: (block))"); + assert_eq!(block_parent.kind(), "parameters"); + assert_eq!(block_parent.to_string(), "(parameters (identifier))"); + assert_eq!(function_definition.to_string(), "(function_definition name: (identifier) parameters: (parameters (identifier)) body: (block))"); } #[test] ```

python.patch

```diff diff --git a/src/grammar.json b/src/grammar.json index 56fdf8e..dac95ec 100644 --- a/src/grammar.json +++ b/src/grammar.json @@ -1647,18 +1647,22 @@ "type": "SYMBOL", "name": "type" } + }, + { + "type": "STRING", + "value": ":" } ] }, + { + "type": "STRING", + "value": ":" + }, { "type": "BLANK" } ] }, - { - "type": "STRING", - "value": ":" - }, { "type": "FIELD", "name": "body", ```

Put both files into the home directory and run this:

git clone https://github.com/tree-sitter/tree-sitter
cd tree-sitter
git reset --hard cbcb51b857
git apply ~/test.patch
script/fetch-fixtures
git -C test/fixtures/grammars/python/ reset --hard a22761025cdac
git -C test/fixtures/grammars/python/ apply ~/python.patch
script/generate-fixtures
script/test

All tests pass.

Expected behavior

(modified) test_parent_of_zero_width_node() should fail since parameters node is not body's immediate parent.

Tree-sitter version (tree-sitter --version)

tree-sitter 0.22.2 (cbcb51b8575ca58f8bfde4f5e78cd08d562faa81)

Operating system/version

Ubuntu 22.04.3 LTS (WSL 2)

[amaanq]

doesn't seem to pass anymore after your reverse iteration pr it seems like, correct me if I'm wrong though

[vanaigr]

I added child_containing_descendant() calls to the end of test_parent_of_zero_width_node() in my pr (#3214), so the original 'test.patch' no longer has all the necessary changes to pass on c19f23f.

https://github.com/tree-sitter/tree-sitter/blob/c19f23f42046d68801c6a99fca34308e4985337e/cli/src/tests/node_test.rs#L287-L291

Updated test.patch:

test.patch

```diff diff --git a/cli/src/tests/node_test.rs b/cli/src/tests/node_test.rs index f226a890..895868ca 100644 --- a/cli/src/tests/node_test.rs +++ b/cli/src/tests/node_test.rs @@ -269,7 +269,7 @@ fn test_node_parent_of_child_by_field_name() { #[test] fn test_parent_of_zero_width_node() { - let code = "def dupa(foo):"; + let code = "def dupa(foo)"; let mut parser = Parser::new(); parser.set_language(&get_language("python")).unwrap(); @@ -277,18 +277,20 @@ fn test_parent_of_zero_width_node() { let tree = parser.parse(code, None).unwrap(); let root = tree.root_node(); let function_definition = root.child(0).unwrap(); - let block = function_definition.child(4).unwrap(); + let parameters = function_definition.child(2).unwrap(); + let block = function_definition.child(3).unwrap(); let block_parent = block.parent().unwrap(); assert_eq!(block.to_string(), "(block)"); - assert_eq!(block_parent.kind(), "function_definition"); - assert_eq!(block_parent.to_string(), "(function_definition name: (identifier) parameters: (parameters (identifier)) body: (block))"); + assert_eq!(block_parent.kind(), "parameters"); + assert_eq!(block_parent.to_string(), "(parameters (identifier))"); + assert_eq!(function_definition.to_string(), "(function_definition name: (identifier) parameters: (parameters (identifier)) body: (block))"); assert_eq!( root.child_containing_descendant(block).unwrap(), function_definition ); - assert_eq!(function_definition.child_containing_descendant(block), None); + assert_eq!(function_definition.child_containing_descendant(block).unwrap(), parameters); } #[test] ```

[amaanq]

thanks for updating