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[pylint] Recurse into subscript subexpressions when searching for list/dict lookups (PLR1733, PLR1736) (#13186)

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## Summary

The `SequenceIndexVisitor` currently does not recurse into
subexpressions of subscripts when searching for subscript accesses that
would trigger this rule. That means that we don't currently detect
violations of the rule on snippets like this:

```py
data = {"a": 1, "b": 2}
column_names = ["a", "b"]
for index, column_name in enumerate(column_names):
    _ = data[column_names[index]]
```

Fixes #13183

## Test Plan

`cargo test -p ruff_linter`
This commit is contained in:
Alex Waygood 2024-09-01 17:22:45 +01:00 • committed by GitHub
parent 2014cba87f
commit 3abd5c08a5
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5 changed files with 90 additions and 16 deletions
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13
crates/ruff_linter/resources/test/fixtures/pylint/unnecessary_dict_index_lookup.py vendored
View file

@ -38,3 +38,16 @@ def value_intentionally_unused():
print(FRUITS[fruit_name]) # OK
blah = FRUITS[fruit_name] # OK
assert FRUITS[fruit_name] == "pear" # OK
def rewrite_client_arrays(value_arrays: dict[str, list[int]]) -> dict[str, list[int]]:
"""Function from https://github.com/zulip/zulip/blob/3da91e951cd03cfa0b9c67378224e348353f36a6/analytics/views/stats.py#L617C1-L626C25"""
mapped_arrays: dict[str, list[int]] = {}
for label, array in value_arrays.items():
mapped_label = client_label_map(label)
if mapped_label in mapped_arrays:
for i in range(len(array)):
mapped_arrays[mapped_label][i] += value_arrays[label][i] # PLR1733
else:
mapped_arrays[mapped_label] = [value_arrays[label][i] for i in range(len(array))] # PLR1733
return mapped_arrays

7
crates/ruff_linter/resources/test/fixtures/pylint/unnecessary_list_index_lookup.py vendored
View file

@ -76,3 +76,10 @@ def start():
# PLR1736
for index, list_item in enumerate(some_list):
print(some_list[index])
def nested_index_lookup():
data = {"a": 1, "b": 2}
column_names = ["a", "b"]
for index, column_name in enumerate(column_names):
_ = data[column_names[index]] # PLR1736

30
crates/ruff_linter/src/rules/pylint/helpers.rs
View file

@ -144,27 +144,25 @@ impl<'a> Visitor<'_> for SequenceIndexVisitor<'a> {
if self.modified {
return;
}
match expr {
Expr::Subscript(ast::ExprSubscript {
value,
slice,
range,
..
}) => {
let Expr::Name(ast::ExprName { id, .. }) = value.as_ref() else {
return;
};
if let Expr::Subscript(ast::ExprSubscript {
value,
slice,
range,
..
}) = expr
{
if let Expr::Name(ast::ExprName { id, .. }) = &**value {
if id == self.sequence_name {
let Expr::Name(ast::ExprName { id, .. }) = slice.as_ref() else {
return;
};
if id == self.index_name {
self.accesses.push(*range);
if let Expr::Name(ast::ExprName { id, .. }) = &**slice {
if id == self.index_name {
self.accesses.push(*range);
}
}
}
}
_ => visitor::walk_expr(self, expr),
}
visitor::walk_expr(self, expr);
}
}

37
crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLR1733_unnecessary_dict_index_lookup.py.snap
View file

@ -121,4 +121,41 @@ unnecessary_dict_index_lookup.py:11:16: PLR1733 [*] Unnecessary lookup of dictio
13 13 |
14 14 | def dont_fix_these():
unnecessary_dict_index_lookup.py:50:51: PLR1733 [*] Unnecessary lookup of dictionary value by key
|
48 | if mapped_label in mapped_arrays:
49 | for i in range(len(array)):
50 | mapped_arrays[mapped_label][i] += value_arrays[label][i] # PLR1733
| ^^^^^^^^^^^^^^^^^^^ PLR1733
51 | else:
52 | mapped_arrays[mapped_label] = [value_arrays[label][i] for i in range(len(array))] # PLR1733
|
= help: Use existing variable
ℹ Safe fix
47 47 | mapped_label = client_label_map(label)
48 48 | if mapped_label in mapped_arrays:
49 49 | for i in range(len(array)):
50 |- mapped_arrays[mapped_label][i] += value_arrays[label][i] # PLR1733
50 |+ mapped_arrays[mapped_label][i] += array[i] # PLR1733
51 51 | else:
52 52 | mapped_arrays[mapped_label] = [value_arrays[label][i] for i in range(len(array))] # PLR1733
53 53 | return mapped_arrays
unnecessary_dict_index_lookup.py:52:44: PLR1733 [*] Unnecessary lookup of dictionary value by key
|
50 | mapped_arrays[mapped_label][i] += value_arrays[label][i] # PLR1733
51 | else:
52 | mapped_arrays[mapped_label] = [value_arrays[label][i] for i in range(len(array))] # PLR1733
| ^^^^^^^^^^^^^^^^^^^ PLR1733
53 | return mapped_arrays
|
= help: Use existing variable
ℹ Safe fix
49 49 | for i in range(len(array)):
50 50 | mapped_arrays[mapped_label][i] += value_arrays[label][i] # PLR1733
51 51 | else:
52 |- mapped_arrays[mapped_label] = [value_arrays[label][i] for i in range(len(array))] # PLR1733
52 |+ mapped_arrays[mapped_label] = [array[i] for i in range(len(array))] # PLR1733
53 53 | return mapped_arrays

19
crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLR1736_unnecessary_list_index_lookup.py.snap
View file

@ -218,3 +218,22 @@ unnecessary_list_index_lookup.py:78:15: PLR1736 [*] List index lookup in `enumer
77 77 | for index, list_item in enumerate(some_list):
78 |- print(some_list[index])
78 |+ print(list_item)
79 79 |
80 80 |
81 81 | def nested_index_lookup():
unnecessary_list_index_lookup.py:85:18: PLR1736 [*] List index lookup in `enumerate()` loop
|
83 | column_names = ["a", "b"]
84 | for index, column_name in enumerate(column_names):
85 | _ = data[column_names[index]] # PLR1736
| ^^^^^^^^^^^^^^^^^^^ PLR1736
|
= help: Use the loop variable directly
ℹ Safe fix
82 82 | data = {"a": 1, "b": 2}
83 83 | column_names = ["a", "b"]
84 84 | for index, column_name in enumerate(column_names):
85 |- _ = data[column_names[index]] # PLR1736
85 |+ _ = data[column_name] # PLR1736