## 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.
## 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>
## Summary
Fixes FURB157 false negative where `Decimal("_-1")` was not flagged as
verbose when underscores precede the sign character. This fixes#21186.
## Problem Analysis
The `verbose-decimal-constructor` (FURB157) rule failed to detect
verbose `Decimal` constructors when the sign character (`+` or `-`) was
preceded by underscores. For example, `Decimal("_-1")` was not flagged,
even though it can be simplified to `Decimal(-1)`.
The bug occurred because the rule checked for the sign character at the
start of the string before stripping leading underscores. According to
Python's `Decimal` parser behavior (as documented in CPython's
`_pydecimal.py`), underscores are removed before parsing the sign. The
rule's logic didn't match this behavior, causing a false negative for
cases like `"_-1"` where the underscore came before the sign.
This was a regression introduced in version 0.14.3, as these cases were
correctly flagged in version 0.14.2.
## Approach
The fix updates the sign extraction logic to:
1. Strip leading underscores first (matching Python's Decimal parser
behavior)
2. Extract the sign from the underscore-stripped string
3. Preserve the string after the sign for normalization purposes
This ensures that cases like `Decimal("_-1")`, `Decimal("_+1")`, and
`Decimal("_-1_000")` are correctly detected and flagged. The
normalization logic was also updated to use the string after the sign
(without underscores) to avoid double signs in the replacement output.
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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
Fixes#20255
Mark single-item-membership-test fixes as always unsafe
- Always set `Applicability::Unsafe` for FURB171 fixes
- Update “Fix safety” docs to reflect always-unsafe behavior
- Expand tests (not in, nested set/frozenset, commented args)
## Test Plan
<!-- How was it tested? -->
I have added new test cases to
`crates/ruff_linter/resources/test/fixtures/refurb/FURB171_0.py` and
`crates/ruff_linter/resources/test/fixtures/refurb/FURB171_1.py`.
---------
Co-authored-by: Brent Westbrook <36778786+ntBre@users.noreply.github.com>
## Summary
Fixes#19076
An attempt at fixing #19076 where the rule could change program behavior
by incorrectly converting from_float/from_decimal method calls to
constructor calls.
The fix implements argument validation using Ruff's existing type
inference system (`ResolvedPythonType`, `typing::is_int`,
`typing::is_float`) to determine when conversions are actually safe,
adds logic to detect invalid method calls (wrong argument counts,
incorrect keyword names) and suppress fixes for them, and changes the
default fix applicability from `Safe` to `Unsafe` with safe fixes only
offered when the argument type is known to be compatible and no
problematic keywords are used.
One uncertainty is whether the type inference catches all possible edge
cases in complex codebases, but the new approach is significantly more
conservative and safer than the previous implementation.
## Test Plan
I updated the existing test fixtures with edge cases from the issue and
manually verified behavior with temporary test files for
valid/unsafe/invalid scenarios.
---------
Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
This PR fixes#19047 / the [isinstance-type-none
(FURB168)](https://docs.astral.sh/ruff/rules/isinstance-type-none/#isinstance-type-none-furb168)
tuple false positive by adding a check if the tuple is empty to the
code. I also noticed there was another false positive with the other
tuple check in the same function, so I fixed it the same way.
`Union[()]` is invalid at runtime with `TypeError: Cannot take a Union
of no types.`, but it is accepted by `basedpyright`
[playground](https://basedpyright.com/?pythonVersion=3.8&typeCheckingMode=all&code=GYJw9gtgBALgngBwJYDsDmUkQWEMoCqKSYKAsAFAgCmAbtQIYA2A%2BvAtQBREkoDanAJQBdQUA)
and is equivalent to `Never`, so I fixed it anyways. I'm getting on a
side tangent here, but it looks like MyPy doesn't accept it, and ty
[playground](https://play.ty.dev/c2c468b6-38e4-4dd9-a9fa-0276e843e395)
gives `@Todo`.
## Test Plan
<!-- How was it tested? -->
Added two test cases for the two false positives.
[playground](https://play.ruff.rs/a53afc21-9a1d-4b9b-9346-abfbeabeb449)
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## Summary
/closes #18639
<!-- What's the purpose of the change? What does it do, and why? -->
## Test Plan
update snapshots
<!-- How was it tested? -->
---------
Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
Summary
--
Fixes#18590 by adding parentheses around lambdas and if expressions in
`for` loop iterators for FURB122 and FURB142. I also updated the docs on
the helper function to reflect the part actually being parenthesized and
the new checks.
The `lambda` case actually causes a `TypeError` at runtime, but I think
it's still worth handling to avoid causing a syntax error.
```pycon
>>> s = set()
... for x in (1,) if True else (2,):
... s.add(-x)
... for x in lambda: 0:
... s.discard(-x)
...
Traceback (most recent call last):
File "<python-input-0>", line 4, in <module>
for x in lambda: 0:
^^^^^^^^^
TypeError: 'function' object is not iterable
```
Test Plan
--
New test cases based on the bug report
---------
Co-authored-by: Dylan <dylwil3@gmail.com>
## Summary
Adds coverage of using set(...) in addition to `{...} in
SingleItemMembershipTest.
Fixes#15792
(and replaces the old PR #15793)
<!-- What's the purpose of the change? What does it do, and why? -->
## Test Plan
Updated unit test and snapshot.
Steps to reproduce are in the issue linked above.
<!-- How was it tested? -->
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## Summary
Fixes#18231
<!-- What's the purpose of the change? What does it do, and why? -->
## Test Plan
Snapshot tests
<!-- How was it tested? -->
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## Summary
We can only guarantee the safety of the autofix for number literals, all
other cases may change the runtime behaviour of the program or introduce
a syntax error. For the cases reported in the issue that would result in
a syntax error, I disabled the autofix.
Follow-up of #17661.
Fixes#16472.
<!-- What's the purpose of the change? What does it do, and why? -->
## Test Plan
Snapshot tests.
<!-- How was it tested? -->
This PR promotes the fix applicability of [readlines-in-for
(FURB129)](https://docs.astral.sh/ruff/rules/readlines-in-for/#readlines-in-for-furb129)
to always safe.
In the original PR (https://github.com/astral-sh/ruff/pull/9880), the
author marked the rule as unsafe because Ruff's type inference couldn't
quite guarantee that we had an `IOBase` object in hand. Some false
positives were recorded in the test fixture. However, before the PR was
merged, Charlie added the necessary type inference and the false
positives went away.
According to the [Python
documentation](https://docs.python.org/3/library/io.html#io.IOBase), I
believe this fix is safe for any proper implementation of `IOBase`:
>[IOBase](https://docs.python.org/3/library/io.html#io.IOBase) (and its
subclasses) supports the iterator protocol, meaning that an
[IOBase](https://docs.python.org/3/library/io.html#io.IOBase) object can
be iterated over yielding the lines in a stream. Lines are defined
slightly differently depending on whether the stream is a binary stream
(yielding bytes), or a text stream (yielding character strings). See
[readline()](https://docs.python.org/3/library/io.html#io.IOBase.readline)
below.
and then in the [documentation for
`readlines`](https://docs.python.org/3/library/io.html#io.IOBase.readlines):
>Read and return a list of lines from the stream. hint can be specified
to control the number of lines read: no more lines will be read if the
total size (in bytes/characters) of all lines so far exceeds hint. [...]
>Note that it’s already possible to iterate on file objects using for
line in file: ... without calling file.readlines().
I believe that a careful reading of our [versioning
policy](https://docs.astral.sh/ruff/versioning/#version-changes)
requires that this change be deferred to a minor release - but please
correct me if I'm wrong!
The PR fixes#16457 .
Specifically, `FURB161` is marked safe, but the rule generates safe
fixes only in specific cases. Therefore, we attempt to mark the fix as
unsafe when we are not in one of these cases.
For instances, the fix is marked as aunsafe just in case of strings (as
pointed out in the issue). Let me know if I should change something.
---------
Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
Fixes false negative when slice bound uses length of string literal.
We were meant to check the following, for example. Given:
```python
text[:bound] if text.endswith(suffix) else text
```
We want to know whether:
- `suffix` is a string literal and `bound` is a number literal
- `suffix` is an expression and `bound` is
exactly `-len(suffix)` (as AST nodes, prior to evaluation.)
The issue is that negative number literals like `-10` are stored as
unary operators applied to a number literal in the AST. So when `suffix`
was a string literal but `bound` was `-len(suffix)` we were getting
caught in the match arm where `bound` needed to be a number. This is now
fixed with a guard.
Closes#16231
## Summary
Added checks for subscript expressions on builtin classes as in FURB189.
The object is changed to use the collections objects and the types from
the subscript are kept.
Resolves#16130
> Note: Added some comments in the code explaining why
## Test Plan
- Added a subscript dict and list class to the test file.
- Tested locally to check that the symbols are changed and the types are
kept.
- No modifications changed on optional `str` values.
## Summary
Resolves#15936.
The fixes will now attempt to preserve the original iterable's format
and quote it if necessary. For `FURB142`, comments within the fix range
will make it unsafe as well.
## Test Plan
`cargo nextest run` and `cargo insta test`.
## Summary
Follow-up to #15779.
Prior to this change, non-name expressions are not reported at all:
```python
type(a.b) is type(None) # no error
```
This change enhances the rule so that such cases are also reported in
preview. Additionally:
* The fix will now be marked as unsafe if there are any comments within
its range.
* Error messages are slightly modified.
## Test Plan
`cargo nextest run` and `cargo insta test`.
---------
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
## Summary
Resolves#10063 and follow-up to #15521.
The fix is now marked as unsafe if there are any comments within its
range. Tests are adapted from that of #15521.
## Test Plan
`cargo nextest run` and `cargo insta test`.
This PR extends the Decimal parsing used in [verbose-decimal-constructor
(FURB157)](https://docs.astral.sh/ruff/rules/verbose-decimal-constructor/)
to better handle non-finite `Decimal` objects, avoiding some false
negatives.
Closes#14587
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
## Summary
It's only safe to enforce the `x in "1234567890"` case if `x` is exactly
one character, since the set on the right has been reordered as compared
to `string.digits`. We can't know if `x` is exactly one character unless
it's a literal. And if it's a literal, well, it's kind of silly code in
the first place?
Closes https://github.com/astral-sh/ruff/issues/13802.
This PR accounts for further subtleties in `Decimal` parsing:
- Strings which are empty modulo underscores and surrounding whitespace
are skipped
- `Decimal("-0")` is skipped
- `Decimal("{integer literal that is longer than 640 digits}")` are
skipped (see linked issue for explanation)
NB: The snapshot did not need to be updated since the new test cases are
"Ok" instances and added below the diff.
Closes#14204
## Summary
Implementation for one of the rules in
https://github.com/astral-sh/ruff/issues/1348
Refurb only deals only with classes with a single base, however the rule
is valid for any base.
(`str, Enum` is common prior to `StrEnum`)
## Test Plan
`cargo test`
---------
Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>
FURB157 suggests replacing expressions like `Decimal("123")` with
`Decimal(123)`. This PR extends the rule to cover cases where the input
string to `Decimal` can be easily transformed into an integer literal.
For example:
```python
Decimal("1__000") # fix: `Decimal(1000)`
```
Note: we do not implement the full decimal parsing logic from CPython on
the grounds that certain acceptable string inputs to the `Decimal`
constructor may be presumed purposeful on the part of the developer. For
example, as in the linked issue, `Decimal("١٢٣")` is valid and equal to
`Decimal(123)`, but we do not suggest a replacement in this case.
Closes#13807
chiri
Dan Parizher
Takayuki Maeda
GiGaGon
Robsdedude
Victor Hugo Gomes
Brent Westbrook
Charlie Marsh
Marcus Näslund
Dylan
Vasco Schiavo
InSync
Vlad Nedelcu
Aleksei Latyshev
Dylan
Alex Waygood
Simon Brugman
Zanie Blue