## Summary
Removes the `module_ptr` field from `AstNodeRef` in release mode, and
change `NodeIndex` to a `NonZeroU32` to reduce the size of
`Option<AstNodeRef<_>>` fields.
I believe CI runs in debug mode, so this won't show up in the memory
report, but this reduces memory by ~2% in release mode.
Parsing the (invalid) expression `f"{\t"i}"` caused a panic because the
`TStringMiddle` character was "unreachable" due the way the parser
recovered from the line continuation (it ate the t-string start).
The cause of the issue is as follows:
The parser begins parsing the f-string and expects to see a list of
objects, essentially alternating between _interpolated elements_ and
ordinary strings. It is happy to see the first left brace, but then
there is a lexical error caused by the line-continuation character. So
instead of the parser seeing a list of elements with just one member, it
sees a list that starts like this:
- Interpolated element with an invalid token, stored as a `Name`
- Something else built from tokens beginning with `TStringStart` and
`TStringMiddle`
When it sees the `TStringStart` error recovery says "that's a list
element I don't know what to do with, let's skip it". When it sees
`TStringMiddle` it says "oh, that looks like the middle of _some
interpolated string_ so let's try to parse it as one of the literal
elements of my `FString`". Unfortunately, the function being used to
parse individual list elements thinks (arguably correctly) that it's not
possible to have a `TStringMiddle` sitting in your `FString`, and hits
`unreachable`.
Two potential ways (among many) to solve this issue are:
1. Allow a `TStringMiddle` as a valid "literal" part of an f-string
during parsing (with the hope/understanding that this would only occur
in an invalid context)
2. Skip the `TStringMiddle` as an "unexpected/invalid list item" in the
same way that we skipped `TStringStart`.
I have opted for the second approach since it seems somehow more morally
correct, even though it loses more information. To implement this, the
recovery context needs to know whether we are in an f-string or t-string
- hence the changes to that enum. As a bonus we get slightly more
specific error messages in some cases.
Closes#18860
## 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.
(Supersedes #9152, authored by @LaBatata101)
## Summary
This PR replaces the current parser generated from LALRPOP to a
hand-written recursive descent parser.
It also updates the grammar for [PEP
646](https://peps.python.org/pep-0646/) so that the parser outputs the
correct AST. For example, in `data[*x]`, the index expression is now a
tuple with a single starred expression instead of just a starred
expression.
Beyond the performance improvements, the parser is also error resilient
and can provide better error messages. The behavior as seen by any
downstream tools isn't changed. That is, the linter and formatter can
still assume that the parser will _stop_ at the first syntax error. This
will be updated in the following months.
For more details about the change here, refer to the PR corresponding to
the individual commits and the release blog post.
## Test Plan
Write _lots_ and _lots_ of tests for both valid and invalid syntax and
verify the output.
## Acknowledgements
- @MichaReiser for reviewing 100+ parser PRs and continuously providing
guidance throughout the project
- @LaBatata101 for initiating the transition to a hand-written parser in
#9152
- @addisoncrump for implementing the fuzzer which helped
[catch](https://github.com/astral-sh/ruff/pull/10903)
[a](https://github.com/astral-sh/ruff/pull/10910)
[lot](https://github.com/astral-sh/ruff/pull/10966)
[of](https://github.com/astral-sh/ruff/pull/10896)
[bugs](https://github.com/astral-sh/ruff/pull/10877)
---------
Co-authored-by: Victor Hugo Gomes <labatata101@linuxmail.org>
Co-authored-by: Micha Reiser <micha@reiser.io>
