mirror of https://github.com/astral-sh/ruff.git synced 2025-09-28 21:05:08 +00:00

[red-knot] Decorators and properties (#17017 )

## Summary

Add support for decorators on function as well as support
for properties by adding special handling for `@property` and `@<name of
property>.setter`/`.getter` decorators.

closes https://github.com/astral-sh/ruff/issues/16987

## Ecosystem results

- ✔️ A lot of false positives are fixed by our new
understanding of properties
- 🔴 A bunch of new false positives (typically
`possibly-unbound-attribute` or `invalid-argument-type`) occur because
we currently do not perform type narrowing on attributes. And with the
new understanding of properties, this becomes even more relevant. In
many cases, the narrowing occurs through an assertion, so this is also
something that we need to implement to get rid of these false positives.
- 🔴 A few new false positives occur because we do not
understand generics, and therefore some calls to custom setters fail.
- 🔴 Similarly, some false positives occur because we do not
understand protocols yet.
- ✔️ Seems like a true positive to me. [The
setter](e624d8edfa/src/packaging/specifiers.py (L752-L754))
only accepts `bools`, but `None` is assigned in [this
line](e624d8edfa/tests/test_specifiers.py (L688)).
  ```
+ error[lint:invalid-assignment]
/tmp/mypy_primer/projects/packaging/tests/test_specifiers.py:688:9:
Invalid assignment to data descriptor attribute `prereleases` on type
`SpecifierSet` with custom `__set__` method
  ```
- ✔️ This is arguable also a true positive. The setter
[here](0c6c75644f/rich/table.py (L359-L363))
returns `Table`, but typeshed wants [setters to return
`None`](bf8d2a9912/stdlib/builtins.pyi (L1298)).
  ```
+ error[lint:invalid-argument-type]
/tmp/mypy_primer/projects/rich/rich/table.py:359:5: Object of type
`Literal[padding]` cannot be assigned to parameter 2 (`fset`) of bound
method `setter`; expected type `(Any, Any, /) -> None`
  ```  

## Follow ups

- Fix the `@no_type_check` regression
- Implement class decorators

## Test Plan

New Markdown test suites for decorators and properties.

2025-04-02 09:27:46 +02:00

3.3 KiB

Raw Blame History

String subscripts

Indexing

s = "abcde"

reveal_type(s[0])  # revealed: Literal["a"]
reveal_type(s[1])  # revealed: Literal["b"]
reveal_type(s[-1])  # revealed: Literal["e"]
reveal_type(s[-2])  # revealed: Literal["d"]

reveal_type(s[False])  # revealed: Literal["a"]
reveal_type(s[True])  # revealed: Literal["b"]

a = s[8]  # error: [index-out-of-bounds] "Index 8 is out of bounds for string `Literal["abcde"]` with length 5"
reveal_type(a)  # revealed: Unknown

b = s[-8]  # error: [index-out-of-bounds] "Index -8 is out of bounds for string `Literal["abcde"]` with length 5"
reveal_type(b)  # revealed: Unknown

def _(n: int):
    a = "abcde"[n]
    # TODO: Support overloads... Should be `str`
    reveal_type(a)  # revealed: @Todo(return type of overloaded function)

Slices

def _(m: int, n: int, s2: str):
    s = "abcde"

    reveal_type(s[0:0])  # revealed: Literal[""]
    reveal_type(s[0:1])  # revealed: Literal["a"]
    reveal_type(s[0:2])  # revealed: Literal["ab"]
    reveal_type(s[0:5])  # revealed: Literal["abcde"]
    reveal_type(s[0:6])  # revealed: Literal["abcde"]
    reveal_type(s[1:3])  # revealed: Literal["bc"]

    reveal_type(s[-3:5])  # revealed: Literal["cde"]
    reveal_type(s[-4:-2])  # revealed: Literal["bc"]
    reveal_type(s[-10:10])  # revealed: Literal["abcde"]

    reveal_type(s[0:])  # revealed: Literal["abcde"]
    reveal_type(s[2:])  # revealed: Literal["cde"]
    reveal_type(s[5:])  # revealed: Literal[""]
    reveal_type(s[:2])  # revealed: Literal["ab"]
    reveal_type(s[:0])  # revealed: Literal[""]
    reveal_type(s[:2])  # revealed: Literal["ab"]
    reveal_type(s[:10])  # revealed: Literal["abcde"]
    reveal_type(s[:])  # revealed: Literal["abcde"]

    reveal_type(s[::-1])  # revealed: Literal["edcba"]
    reveal_type(s[::2])  # revealed: Literal["ace"]
    reveal_type(s[-2:-5:-1])  # revealed: Literal["dcb"]
    reveal_type(s[::-2])  # revealed: Literal["eca"]
    reveal_type(s[-1::-3])  # revealed: Literal["eb"]

    reveal_type(s[None:2:None])  # revealed: Literal["ab"]
    reveal_type(s[1:None:1])  # revealed: Literal["bcde"]
    reveal_type(s[None:None:None])  # revealed: Literal["abcde"]

    start = 1
    stop = None
    step = 2
    reveal_type(s[start:stop:step])  # revealed: Literal["bd"]

    reveal_type(s[False:True])  # revealed: Literal["a"]
    reveal_type(s[True:3])  # revealed: Literal["bc"]

    s[0:4:0]  # error: [zero-stepsize-in-slice]
    s[:4:0]  # error: [zero-stepsize-in-slice]
    s[0::0]  # error: [zero-stepsize-in-slice]
    s[::0]  # error: [zero-stepsize-in-slice]

    substring1 = s[m:n]
    # TODO: Support overloads... Should be `LiteralString`
    reveal_type(substring1)  # revealed: @Todo(return type of overloaded function)

    substring2 = s2[0:5]
    # TODO: Support overloads... Should be `str`
    reveal_type(substring2)  # revealed: @Todo(return type of overloaded function)

Unsupported slice types

# TODO: It would be great if we raised an error here. This can be done once
# we have support for overloads and generics, and once typeshed has a more
# precise annotation for `str.__getitem__`, that makes use of the generic
# `slice[..]` type. We could then infer `slice[str, str]` here and see that
# it doesn't match the signature of `str.__getitem__`.
"foo"["bar":"baz"]

3.3 KiB Raw Blame History

String subscripts

Indexing

Slices

Unsupported slice types

3.3 KiB

Raw Blame History