## Summary
Fix https://github.com/astral-sh/ty/issues/664
This PR adds support for storing attributes in comprehension scopes (any
eager scope.)
For example in the following code we infer type of `z` correctly:
```py
class C:
def __init__(self):
[None for self.z in range(1)]
reveal_type(C().z) # previously [unresolved-attribute] but now shows Unknown | int
```
The fix works by adjusting the following logics:
To identify if an attriute is an assignment to self or cls we need to
check the scope is a method. To allow comprehension scopes here we skip
any eager scope in the check.
Also at this stage the code checks if self or the first method argument
is shadowed by another binding that eager scope to prevent this:
```py
class D:
g: int
class C:
def __init__(self):
[[None for self.g in range(1)] for self in [D()]]
reveal_type(C().g) # [unresolved-attribute]
```
When determining scopes that attributes might be defined after
collecting all the methods of the class the code also returns any
decendant scope that is eager and only has eager parents until the
method scope.
When checking reachability of a attribute definition if the attribute is
defined in an eager scope we use the reachability of the first non eager
scope which must be a method. This allows attributes to be marked as
reachable and be seen.
There are also which I didn't add support for:
```py
class C:
def __init__(self):
def f():
[None for self.z in range(1)]
f()
reveal_type(C().z) # [unresolved-attribute]
```
In the above example we will not even return the comprehension scope as
an attribute scope because there is a non eager scope (`f` function)
between the comprehension and the `__init__` method
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
It looks like VS Code does this forcefully. As in, I don't think we can
override it. It also seems like a plausibly good idea. But by us doing
it too, it makes our completion evaluation framework match real world
conditions. (To the extent that "VS Code" and "real world conditions"
are the same. Which... they aren't. But it's close, since VS Code is so
popular.)
This should round out the rest of the set. I think I had hesitated doing
this before because some of these don't make sense in every context. But
I think identifying the correct context for every keyword could be quite
difficult. And at the very least, I think offering these at least as a
choice---even if they aren't always correct---is better than not doing
it at all.
## Summary
Fixes https://github.com/astral-sh/ty/issues/1409
This PR allows `Final` instance attributes to be initialized in
`__init__` methods, as mandated by the Python typing specification (PEP
591). Previously, ty incorrectly prevented this initialization, causing
false positive errors.
The fix checks if we're inside an `__init__` method before rejecting
Final attribute assignments, allowing assignments during
instance initialization while still preventing reassignment elsewhere.
## Test Plan
- Added new test coverage in `final.md` for the reported issue with
`Self` annotations
- Updated existing tests that were incorrectly expecting errors
- All 278 mdtest tests pass
- Manually tested with real-world code examples
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
Fixes https://github.com/astral-sh/ty/issues/1487
This one is a true extension of non-standard semantics, and is therefore
a certified Hot Take we might conclude is simply a Bad Take (let's see
what ecosystem tests say...).
By resolving `.` and the LHS of the from import during semantic
indexing, we can check if the LHS is a submodule of `.`, and handle
`from whatever.thispackage.x.y import z` exactly like we do `from .x.y
import z`.
Fixes https://github.com/astral-sh/ty/issues/1484
This manifested as an error when inferring the type of a PEP-695 generic
class via its constructor parameters:
```py
class D[T, U]:
@overload
def __init__(self: "D[str, U]", u: U) -> None: ...
@overload
def __init__(self, t: T, u: U) -> None: ...
def __init__(self, *args) -> None: ...
# revealed: D[Unknown, str]
# SHOULD BE: D[str, str]
reveal_type(D("string"))
```
This manifested because `D` is inferred to be bivariant in both `T` and
`U`. We weren't seeing this in the equivalent example for legacy
typevars, since those default to invariant. (This issue also showed up
for _covariant_ typevars, so this issue was not limited to bivariance.)
The underlying cause was because of a heuristic that we have in our
current constraint solver, which attempts to handle situations like
this:
```py
def f[T](t: T | None): ...
f(None)
```
Here, the `None` argument matches the non-typevar union element, so this
argument should not add any constraints on what `T` can specialize to.
Our previous heuristic would check for this by seeing if the argument
type is a subtype of the parameter annotation as a whole — even if it
isn't a union! That would cause us to erroneously ignore the `self`
parameter in our constructor call, since bivariant classes are
equivalent to each other, regardless of their specializations.
The quick fix is to move this heuristic "down a level", so that we only
apply it when the parameter annotation is a union. This heuristic should
go away completely 🤞 with the new constraint solver.
This loses any ability to have "per-function" implicit submodule
imports, to avoid the "ok but now we need per-scope imports" and "ok but
this should actually introduce a global that only exists during this
function" problems. A simple and clean implementation with no weird
corners.
Fixes https://github.com/astral-sh/ty/issues/1482
This rips out the previous implementation in favour of a new
implementation with 3 rules:
- **froms are locals**: a `from..import` can only define locals, it does
not have global
side-effects. Specifically any submodule attribute `a` that's implicitly
introduced by either
`from .a import b` or `from . import a as b` (in an `__init__.py(i)`) is
a local and not a
global. If you do such an import at the top of a file you won't notice
this. However if you do
such an import in a function, that means it will only be function-scoped
(so you'll need to do
it in every function that wants to access it, making your code less
sensitive to execution
order).
- **first from first serve**: only the *first* `from..import` in an
`__init__.py(i)` that imports a
particular direct submodule of the current package introduces that
submodule as a local.
Subsequent imports of the submodule will not introduce that local. This
reflects the fact that
in actual python only the first import of a submodule (in the entire
execution of the program)
introduces it as an attribute of the package. By "first" we mean "the
first time in this scope
(or any parent scope)". This pairs well with the fact that we are
specifically introducing a
local (as long as you don't accidentally shadow or overwrite the local).
- **dot re-exports**: `from . import a` in an `__init__.pyi` is
considered a re-export of `a`
(equivalent to `from . import a as a`). This is required to properly
handle many stubs in the
wild. Currently it must be *exactly* `from . import ...`.
This implementation is intentionally limited/conservative (notably,
often requiring a from import to be relative). I'm going to file a ton
of followups for improvements so that their impact can be evaluated
separately.
Fixes https://github.com/astral-sh/ty/issues/133
## Summary
Fixed RUF065 (`logging-eager-conversion`) to only flag `str()` calls
when they perform a simple conversion that can be safely removed. The
rule now ignores `str()` calls with no arguments, multiple arguments,
starred arguments, or keyword unpacking, preventing false positives.
Fixes#21315
## Problem Analysis
The RUF065 rule was incorrectly flagging all `str()` calls in logging
statements, even when `str()` was performing actual conversion work
beyond simple type coercion. Specifically, the rule flagged:
- `str()` with no arguments - which returns an empty string
- `str(b"data", "utf-8")` with multiple arguments - which performs
encoding conversion
- `str(*args)` with starred arguments - which unpacks arguments
- `str(**kwargs)` with keyword unpacking - which passes keyword
arguments
These cases cannot be safely removed because `str()` is doing meaningful
work (encoding conversion, argument unpacking, etc.), not just redundant
type conversion.
The root cause was that the rule only checked if the function was
`str()` without validating the call signature. It didn't distinguish
between simple `str(value)` conversions (which can be removed) and more
complex `str()` calls that perform actual work.
## Approach
The fix adds validation to the `str()` detection logic in
`logging_eager_conversion.rs`:
1. **Check argument count**: Only flag `str()` calls with exactly one
positional argument (`str_call_args.args.len() == 1`)
2. **Check for starred arguments**: Ensure the single argument is not
starred (`!str_call_args.args[0].is_starred_expr()`)
3. **Check for keyword arguments**: Ensure there are no keyword
arguments (`str_call_args.keywords.is_empty()`)
This ensures the rule only flags cases like `str(value)` where `str()`
is truly redundant and can be removed, while ignoring cases where
`str()` performs actual conversion work.
The fix maintains backward compatibility - all existing valid test cases
continue to be flagged correctly, while the new edge cases are properly
ignored.
---------
Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
It's everyone's favourite language corner case!
Also having kicked the tires on it, I'm pretty happy to call this (in
conjunction with #21367):
Fixes https://github.com/astral-sh/ty/issues/494
There's cases where you can make noisy Literal hints appear, so we can
always iterate on it, but this handles like, 98% of the cases in the
wild, which is great.
---------
Co-authored-by: David Peter <sharkdp@users.noreply.github.com>
I'm not 100% sold on this implementation, but it's a strict improvement
and it adds a ton of snapshot tests for future iteration.
Part of https://github.com/astral-sh/ty/issues/494
## Summary
Fixes FURB105 (`print-empty-string`) to detect empty f-strings in
addition to regular empty strings. Previously, the rule only flagged
`print("")` but missed `print(f"")`. This fix ensures both cases are
detected and can be automatically fixed.
Fixes#21346
## Problem Analysis
The FURB105 rule checks for unnecessary empty strings passed to
`print()` calls. The `is_empty_string` helper function was only checking
for `Expr::StringLiteral` with empty values, but did not handle
`Expr::FString` (f-strings). As a result, `print(f"")` was not being
flagged as a violation, even though it's semantically equivalent to
`print("")` and should be simplified to `print()`.
The issue occurred because the function used a `matches!` macro that
only checked for string literals:
```rust
fn is_empty_string(expr: &Expr) -> bool {
matches!(
expr,
Expr::StringLiteral(ast::ExprStringLiteral { value, .. }) if value.is_empty()
)
}
```
## Approach
1. **Import the helper function**: Added `is_empty_f_string` to the
imports from `ruff_python_ast::helpers`, which already provides logic to
detect empty f-strings.
2. **Update `is_empty_string` function**: Changed the implementation
from a `matches!` macro to a `match` expression that handles both string
literals and f-strings:
```rust
fn is_empty_string(expr: &Expr) -> bool {
match expr {
Expr::StringLiteral(ast::ExprStringLiteral { value, .. }) =>
value.is_empty(),
Expr::FString(f_string) => is_empty_f_string(f_string),
_ => false,
}
}
```
The fix leverages the existing `is_empty_f_string` helper function which
properly handles the complexity of f-strings, including nested f-strings
and interpolated expressions. This ensures the detection is accurate and
consistent with how empty strings are detected elsewhere in the
codebase.
<!--
Thank you for contributing to Ruff/ty! To help us out with reviewing,
please consider the following:
- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title? (Please prefix
with `[ty]` for ty pull
requests.)
- Does this pull request include references to any relevant issues?
-->
## Summary
Resolves https://github.com/astral-sh/ty/issues/1494
## Test Plan
Add a test showing if we are in `from <name> <name> ` we provide the
keyword completion "import"
This elides the following inlay hints:
```py
foo([x=]x)
foo([x=]y.x)
foo([x=]x[0])
foo([x=]x(...))
# composes to complex situations
foo([x=]y.x(..)[0])
```
Fixes https://github.com/astral-sh/ty/issues/1514
Summary
--
Fixes#21360 by using the union of names instead of overwriting them, as
Micha suggested originally on #21104.
This avoids overwriting the `n` name in the `Subscript` by the empty set
of names visited in the nested OR pattern before visiting the other arm
of the outer OR pattern.
Test Plan
--
A new inline test case taken from the issue
## Summary
Detect usages of implicit `self` in property getters, which allows us to
treat their signature as being generic.
closes https://github.com/astral-sh/ty/issues/1502
## Typing conformance
Two new type assertions that are succeeding.
## Ecosystem results
Mostly look good. There are a few new false positives related to a bug
with constrained typevars that is unrelated to the work here. I reported
this as https://github.com/astral-sh/ty/issues/1503.
## Test Plan
Added regression tests.
## Summary
Add support for `Optional` and `Annotated` in implicit type aliases
part of https://github.com/astral-sh/ty/issues/221
## Typing conformance changes
New expected diagnostics.
## Ecosystem
A lot of true positives, some known limitations unrelated to this PR.
## Test Plan
New Markdown tests
## Summary
This PR adds extra validation for `isinstance()` and `issubclass()`
calls that use `UnionType` instances for their second argument.
According to typeshed's annotations, any `UnionType` is accepted for the
second argument, but this isn't true at runtime: at runtime, all
elements in the `UnionType` must either be class objects or be `None` in
order for the `isinstance()` or `issubclass()` call to reliably succeed:
```pycon
% uvx python3.14
Python 3.14.0 (main, Oct 10 2025, 12:54:13) [Clang 20.1.4 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from typing import LiteralString
>>> import types
>>> type(LiteralString | int) is types.UnionType
True
>>> isinstance(42, LiteralString | int)
Traceback (most recent call last):
File "<python-input-5>", line 1, in <module>
isinstance(42, LiteralString | int)
~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/Library/Application Support/uv/python/cpython-3.14.0-macos-aarch64-none/lib/python3.14/typing.py", line 559, in __instancecheck__
raise TypeError(f"{self} cannot be used with isinstance()")
TypeError: typing.LiteralString cannot be used with isinstance()
```
## Test Plan
Added mdtests/snapshots
## Summary
Fixed FURB101 (`read-whole-file`) to handle annotated assignments.
Previously, the rule would detect violations in code like `contents: str
= f.read()` but fail to generate a fix. Now it correctly generates fixes
that preserve type annotations (e.g., `contents: str =
Path("file.txt").read_text(encoding="utf-8")`).
Fixes#21274
## Problem Analysis
The FURB101 rule was only checking for `Stmt::Assign` statements when
determining whether a fix could be applied. When encountering annotated
assignments (`Stmt::AnnAssign`) like `contents: str = f.read()`, the
rule would:
1. Correctly detect the violation (the diagnostic was reported)
2. Fail to generate a fix because:
- The `visit_expr` method only matched `Stmt::Assign`, not
`Stmt::AnnAssign`
- The `generate_fix` function only accepted `Stmt::Assign` in its body
validation
- The replacement code generation didn't account for type annotations
This occurred because Python's AST represents annotated assignments as a
different node type (`StmtAnnAssign`) with separate fields for the
target, annotation, and value, unlike regular assignments which use a
list of targets.
## Approach
The fix extends the rule to handle both assignment types:
1. **Updated `visit_expr` method**: Now matches both `Stmt::Assign` and
`Stmt::AnnAssign`, extracting:
- Variable name from the target expression
- Type annotation code (when present) using the code generator
2. **Updated `generate_fix` function**:
- Added `annotation: Option<String>` parameter to accept annotation code
- Updated body validation to accept both `Stmt::Assign` and
`Stmt::AnnAssign`
- Modified replacement code generation to preserve annotations: `{var}:
{annotation} = {binding}({filename_code}).{suggestion}`
3. **Added test case**: Added an annotated assignment test case to
verify the fix works correctly.
The implementation maintains backward compatibility with regular
assignments while adding support for annotated assignments, ensuring
type annotations are preserved in the generated fixes.
---------
Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
We have lots of `TypeVisitor`s that end up having very similar
`visit_type` implementations. This PR consolidates some of the code for
these so that there's less repetition and duplication.
When checking whether a constraint set is satisfied, if a typevar has a
non-fully-static upper bound or constraint, we are free to choose any
materialization that makes the check succeed.
In non-inferable positions, we have to show that the constraint set is
satisfied for all valid specializations, so it's best to choose the most
restrictive materialization, since that minimizes the set of valid
specializations that have to pass.
In inferable positions, we only have to show that the constraint set is
satisfied for _some_ valid specializations, so it's best to choose the
most permissive materialization, since that maximizes our chances of
finding a specialization that passes.
Summary
--
These rules are themselves in preview, so we don't need the additional
preview checks on the fixes or the separate preview tests. This has
confused me in a couple of reviews of changes to the fixes.
Test Plan
--
Existing tests, with the fixes previously only shown in the preview
tests now in the "non-preview" tests.
## Summary
Add support for `Literal` types in implicit type aliases.
part of https://github.com/astral-sh/ty/issues/221
## Ecosystem analysis
This looks good to me, true positives and known problems.
## Test Plan
New Markdown tests.
## Summary
This PR adds support for understanding the legacy definition and PEP 695
definition for `ParamSpec`.
This is still very initial and doesn't really implement any of the
semantics.
Part of https://github.com/astral-sh/ty/issues/157
## Test Plan
Add mdtest cases.
## Ecosystem analysis
Most of the diagnostics in `starlette` are due to the fact that ty now
understands `ParamSpec` is not a `Todo` type, so the assignability check
fails. The code looks something like:
```py
class _MiddlewareFactory(Protocol[P]):
def __call__(self, app: ASGIApp, /, *args: P.args, **kwargs: P.kwargs) -> ASGIApp: ... # pragma: no cover
class Middleware:
def __init__(
self,
cls: _MiddlewareFactory[P],
*args: P.args,
**kwargs: P.kwargs,
) -> None:
self.cls = cls
self.args = args
self.kwargs = kwargs
# ty complains that `ServerErrorMiddleware` is not assignable to `_MiddlewareFactory[P]`
Middleware(ServerErrorMiddleware, handler=error_handler, debug=debug)
```
There are multiple diagnostics where there's an attribute access on the
`Wrapped` object of `functools` which Pyright also raises:
```py
from functools import wraps
def my_decorator(f):
@wraps(f)
def wrapper(*args, **kwds):
return f(*args, **kwds)
# Pyright: Cannot access attribute "__signature__" for class "_Wrapped[..., Unknown, ..., Unknown]"
Attribute "__signature__" is unknown [reportAttributeAccessIssue]
# ty: Object of type `_Wrapped[Unknown, Unknown, Unknown, Unknown]` has no attribute `__signature__` [unresolved-attribute]
wrapper.__signature__
return wrapper
```
There are additional diagnostics that is due to the assignability checks
failing because ty now infers the `ParamSpec` instead of using the
`Todo` type which would always succeed. This results in a few
`no-matching-overload` diagnostics because the assignability checks
fail.
There are a few diagnostics related to
https://github.com/astral-sh/ty/issues/491 where there's a variable
which is either a bound method or a variable that's annotated with
`Callable` that doesn't contain the instance as the first parameter.
Another set of (valid) diagnostics are where the code hasn't provided
all the type variables. ty is now raising diagnostics for these because
we include `ParamSpec` type variable in the signature. For example,
`staticmethod[Any]` which contains two type variables.
<!--
Thank you for contributing to Ruff/ty! To help us out with reviewing,
please consider the following:
- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title? (Please prefix
with `[ty]` for ty pull
requests.)
- Does this pull request include references to any relevant issues?
-->
## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
Closes https://github.com/astral-sh/ty/issues/989
There are various situations where users expect the Python packages
installed in the same environment as ty itself to be considered during
type checking. A minimal example would look like:
```
uv venv my-env
uv pip install my-env ty httpx
echo "import httpx" > foo.py
./my-env/bin/ty check foo.py
```
or
```
uv tool install ty --with httpx
echo "import httpx" > foo.py
ty check foo.py
```
While these are a bit contrived, there are real-world situations where a
user would expect a similar behavior to work. Notably, all of the other
type checkers consider their own environment when determining search
paths (though I'll admit that I have not verified when they choose not
to do this).
One common situation where users are encountering this today is with
`uvx --with-requirements script.py ty check script.py` — which is
currently our "best" recommendation for type checking a PEP 723 script,
but it doesn't work.
Of the options discussed in
https://github.com/astral-sh/ty/issues/989#issuecomment-3307417985, I've
chosen (2) as our criteria for including ty's environment in the search
paths.
- If no virtual environment is discovered, we will always include ty's
environment.
- If a `.venv` is discovered in the working directory, we will _prepend_
ty's environment to the search paths. The dependencies in ty's
environment (e.g., from `uvx --with`) will take precedence.
- If a virtual environment is active, e.g., `VIRTUAL_ENV` (i.e.,
including conda prefixes) is set, we will not include ty's environment.
The reason we need to special case the `.venv` case is that we both
1. Recommend `uvx ty` today as a way to check your project
2. Want to enable `uvx --with <...> ty`
And I don't want (2) to break when you _happen_ to be in a project
(i.e., if we only included ty's environment when _no_ environment is
found) and don't want to remove support for (1).
I think long-term, I want to make `uvx <cmd>` layer the environment on
_top_ of the project environment (in uv), which would obviate the need
for this change when you're using uv. However, that change is breaking
and I think users will expect this behavior in contexts where they're
not using uv, so I think we should handle it in ty regardless.
I've opted not to include the environment if it's non-virtual (i.e., a
system environment) for now. It seems better to start by being more
restrictive. I left a comment in the code.
## Test Plan
I did some manual testing with the initial commit, then subsequently
added some unit tests.
```
❯ echo "import httpx" > example.py
❯ uvx --with httpx ty check example.py
Installed 8 packages in 19ms
error[unresolved-import]: Cannot resolve imported module `httpx`
--> foo/example.py:1:8
|
1 | import httpx
| ^^^^^
|
info: Searched in the following paths during module resolution:
info: 1. /Users/zb/workspace/ty/python (first-party code)
info: 2. /Users/zb/workspace/ty (first-party code)
info: 3. vendored://stdlib (stdlib typeshed stubs vendored by ty)
info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
info: rule `unresolved-import` is enabled by default
Found 1 diagnostic
❯ uvx --from . --with httpx ty check example.py
All checks passed!
```
```
❯ uv init --script foo.py
Initialized script at `foo.py`
❯ uv add --script foo.py httpx
warning: The Python request from `.python-version` resolved to Python 3.13.8, which is incompatible with the script's Python requirement: `>=3.14`
Updated `foo.py`
❯ echo "import httpx" >> foo.py
❯ uvx --with-requirements foo.py ty check foo.py
error[unresolved-import]: Cannot resolve imported module `httpx`
--> foo.py:15:8
|
13 | if __name__ == "__main__":
14 | main()
15 | import httpx
| ^^^^^
|
info: Searched in the following paths during module resolution:
info: 1. /Users/zb/workspace/ty/python (first-party code)
info: 2. /Users/zb/workspace/ty (first-party code)
info: 3. vendored://stdlib (stdlib typeshed stubs vendored by ty)
info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
info: rule `unresolved-import` is enabled by default
Found 1 diagnostic
❯ uvx --from . --with-requirements foo.py ty check foo.py
All checks passed!
```
Notice we do not include ty's environment if `VIRTUAL_ENV` is set
```
❯ VIRTUAL_ENV=.venv uvx --with httpx ty check foo/example.py
error[unresolved-import]: Cannot resolve imported module `httpx`
--> foo/example.py:1:8
|
1 | import httpx
| ^^^^^
|
info: Searched in the following paths during module resolution:
info: 1. /Users/zb/workspace/ty/python (first-party code)
info: 2. /Users/zb/workspace/ty (first-party code)
info: 3. vendored://stdlib (stdlib typeshed stubs vendored by ty)
info: 4. /Users/zb/workspace/ty/.venv/lib/python3.13/site-packages (site-packages)
info: make sure your Python environment is properly configured: https://docs.astral.sh/ty/modules/#python-environment
info: rule `unresolved-import` is enabled by default
Found 1 diagnostic
```
