ruff/crates/ruff_python_parser/tests/snapshots/valid_syntax@walrus_py38.py.snap
Ibraheem Ahmed c9dff5c7d5
[ty] AST garbage collection (#18482)
## Summary

Garbage collect ASTs once we are done checking a given file. Queries
with a cross-file dependency on the AST will reparse the file on demand.
This reduces ty's peak memory usage by ~20-30%.

The primary change of this PR is adding a `node_index` field to every
AST node, that is assigned by the parser. `ParsedModule` can use this to
create a flat index of AST nodes any time the file is parsed (or
reparsed). This allows `AstNodeRef` to simply index into the current
instance of the `ParsedModule`, instead of storing a pointer directly.

The indices are somewhat hackily (using an atomic integer) assigned by
the `parsed_module` query instead of by the parser directly. Assigning
the indices in source-order in the (recursive) parser turns out to be
difficult, and collecting the nodes during semantic indexing is
impossible as `SemanticIndex` does not hold onto a specific
`ParsedModuleRef`, which the pointers in the flat AST are tied to. This
means that we have to do an extra AST traversal to assign and collect
the nodes into a flat index, but the small performance impact (~3% on
cold runs) seems worth it for the memory savings.

Part of https://github.com/astral-sh/ty/issues/214.
2025-06-13 08:40:11 -04:00

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1.4 KiB
Text

---
source: crates/ruff_python_parser/tests/fixtures.rs
input_file: crates/ruff_python_parser/resources/inline/ok/walrus_py38.py
---
## AST
```
Module(
ModModule {
node_index: AtomicNodeIndex(..),
range: 0..54,
body: [
Expr(
StmtExpr {
node_index: AtomicNodeIndex(..),
range: 45..53,
value: Named(
ExprNamed {
node_index: AtomicNodeIndex(..),
range: 46..52,
target: Name(
ExprName {
node_index: AtomicNodeIndex(..),
range: 46..47,
id: Name("x"),
ctx: Store,
},
),
value: NumberLiteral(
ExprNumberLiteral {
node_index: AtomicNodeIndex(..),
range: 51..52,
value: Int(
1,
),
},
),
},
),
},
),
],
},
)
```