This pull request fixes the bug described in issue
[#19153](https://github.com/astral-sh/ruff/issues/19153).
The issue occurred when `PERF403` incorrectly flagged cases involving
tuple unpacking in a for loop. For example:
```python
def f():
v = {}
for (o, p), x in [("op", "x")]:
v[x] = o, p
```
This code was wrongly suggested to be rewritten into a dictionary
comprehension, which changes the semantics.
Changes in this PR:
Updated the `PERF403` rule to correctly handle tuple unpacking in loop
targets.
Added regression tests to ensure this case (and similar ones) are no
longer flagged incorrectly.
Why:
This ensures that `PERF403` only triggers when a dictionary
comprehension is semantically equivalent to the original loop,
preventing false positives.
---------
Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>
## Summary
Resolves#19531
I've implemented a check to determine whether the for_stmt target is
declared as global or nonlocal. I believe we should skip the rule in all
such cases, since variables declared this way are intended for use
outside the loop scope, making value changes expected behavior.
## Test Plan
Added two test cases for global and nonlocal variable to snapshot.
## Summary
closes#19204
## Test Plan
1. test case is added in dedicated file
2. locally tested the code manually
---------
Co-authored-by: Brent Westbrook <36778786+ntBre@users.noreply.github.com>
Co-authored-by: CodeMan62 <sharmahimanshu150082007@gmail.com>
This is an implementation of the discussion from #16719.
This change will allow list function calls to be replaced with
comprehensions:
```python
result = list()
for i in range(3):
result.append(i + 1)
# becomes
result = [i + 1 for i in range(3)]
```
I added a new test to `PERF401.py` to verify that this fix will now work
for `list()`.
## Summary
This change adds an auto-fix for manual dict comprehensions. It also
copies many of the improvements from #13919 (and associated PRs fixing
issues with it), and moves some of the utility functions from
`manual_list_comprehension.rs` into a separate `helpers.rs` to be used
in both.
## Test Plan
I added a preview test case to showcase the new fix and added a test
case in `PERF403.py` to make sure lines with semicolons function. I
didn't yet make similar tests to the ones I added earlier to
`PERF401.py`, but the logic is the same, so it might be good to add
those to make sure they work.
Fixes#15012.
```python
def f():
# panics when the code can't find the loop variable
values = [1, 2, 3]
result = []
for i in values:
result.append(i + 1)
del i
```
I'm not sure exactly why this test case panics, but I suspect the `del
i` removes the binding from the semantic model's symbols.
I changed the code to search for the correct binding by directly
iterating through the bindings. Since we know exactly which binding we
want, this should find the loop variable without any complications.
Fixes#14969.
The issue was that this line:
```rust
let from_assign_to_loop = TextRange::new(binding_stmt.end(), for_stmt.start());
```
was not safe if the binding was after the target. The only way (at least
that I can think of) this can happen is if they are in different scopes,
so it now checks for that before checking if there are usages between
the two.
## Summary
This PR ensures that if a list `x` is modified within a `for` loop, we
avoid flagging `list(x)` as unnecessary. Previously, we only detected
calls to exactly `.append`, and they couldn't be nested within other
statements.
Closes https://github.com/astral-sh/ruff/issues/9925.
## Summary
Adds `find_assigned_value` a function which gets the `&Expr` assigned to
a given `id` if one exists in the semantic model.
Open TODOs:
- [ ] Handle `binding.kind.is_unpacked_assignment()`: I am bit confused
by this one. The snippet from its documentation does not appear to be
counted as an unpacked assignment and the only ones I could find for
which that was true were invalid Python like:
```python
x, y = 1
```
- [ ] How to handle AugAssign. Can we combine statements like:
```python
(a, b) = [(1, 2, 3), (4,)]
a += (6, 7)
```
to get the full value for a? Code currently just returns `None` for
these assign types
- [ ] Multi target assigns
```python
m_c = (m_d, m_e) = (0, 0)
trio.sleep(m_c) # OK
trio.sleep(m_d) # TRIO115
trio.sleep(m_e) # TRIO115
```
## Test Plan
Used the function in two rules:
- `TRIO115`
- `PERF101`
Expanded both their fixtures for explicit multi target check
Lior Weissman
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