## 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.
Previously an error was emitted any time the configuration required both
an import of a module and an alias for that module. However, required
imports could themselves contain an alias, which may or may not agree
with the required alias.
To wit: requiring `import pandas as pd` does not conflict with the
`flake8-import-conventions.alias` config `{"pandas":"pd"}`.
This PR refines the check before throwing an error.
Closes#15911
## Summary
This fixes the infinite loop reported in #14389 by raising an error to
the user about conflicting ICN001 (`unconventional-import-alias`) and
I002 (`missing-required-import`) configuration options.
## Test Plan
Added a CLI integration test reproducing the old behavior and then
confirming the fix.
Closes#14389
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
## Summary
If an import is marked as "required", we should never flag it as unused.
In practice, this is rare, since required imports are typically used for
`__future__` annotations, which are always considered "used".
Closes https://github.com/astral-sh/ruff/issues/12458.
