[flake8-pytest-style] Allow for loops with empty bodies (PT012, PT031) (#16678)

## Summary

This PR stabilizes the behavior change introduced in
https://github.com/astral-sh/ruff/pull/15542 to allow
for statements with an empty body in `pytest.raises` and `pytest.warns`
with statements.

This raised an error before but is now allowed:

```py
with pytest.raises(KeyError, match='unknown'):
    async for _ in gpt.generate(gpt_request):
        pass
```

The same applies to 

```py
with pytest.raises(KeyError, match='unknown'):
    async for _ in gpt.generate(gpt_request):
        ...
```


There have been now new issues or PRs related to PT012 or PT031 since
this behavior change was introduced in ruff 0.9.3 (January 23rd).

crates/ruff_linter/src/rules/flake8_pytest_style/mod.rs

@@ -11,7 +11,7 @@ mod tests {
     use test_case::test_case;
 
     use crate::registry::Rule;
-    use crate::settings::types::{IdentifierPattern, PreviewMode};
+    use crate::settings::types::IdentifierPattern;
     use crate::test::test_path;
     use crate::{assert_messages, settings};
 
@@ -358,36 +358,6 @@ mod tests {
         Ok(())
     }
 
-    #[test_case(
-        Rule::PytestRaisesWithMultipleStatements,
-        Path::new("PT012.py"),
-        Settings::default(),
-        "PT012_preview"
-    )]
-    #[test_case(
-        Rule::PytestWarnsWithMultipleStatements,
-        Path::new("PT031.py"),
-        Settings::default(),
-        "PT031_preview"
-    )]
-    fn test_pytest_style_preview(
-        rule_code: Rule,
-        path: &Path,
-        plugin_settings: Settings,
-        name: &str,
-    ) -> Result<()> {
-        let diagnostics = test_path(
-            Path::new("flake8_pytest_style").join(path).as_path(),
-            &settings::LinterSettings {
-                preview: PreviewMode::Enabled,
-                flake8_pytest_style: plugin_settings,
-                ..settings::LinterSettings::for_rule(rule_code)
-            },
-        )?;
-        assert_messages!(name, diagnostics);
-        Ok(())
-    }
-
     /// This test ensure that PT006 and PT007 don't conflict when both of them suggest a fix that
     /// edits `argvalues` for `pytest.mark.parametrize`.
     #[test]

crates/ruff_linter/src/rules/flake8_pytest_style/rules/raises.rs

@@ -13,6 +13,10 @@ use super::helpers::is_empty_or_null_string;
 /// ## What it does
 /// Checks for `pytest.raises` context managers with multiple statements.
 ///
+/// This rule allows `pytest.raises` bodies to contain `for`
+/// loops with empty bodies (e.g., `pass` or `...` statements), to test
+/// iterator behavior.
+///
 /// ## Why is this bad?
 /// When a `pytest.raises` is used as a context manager and contains multiple
 /// statements, it can lead to the test passing when it actually should fail.
@@ -20,10 +24,6 @@ use super::helpers::is_empty_or_null_string;
 /// A `pytest.raises` context manager should only contain a single simple
 /// statement that raises the expected exception.
 ///
-/// In [preview], this rule allows `pytest.raises` bodies to contain `for`
-/// loops with empty bodies (e.g., `pass` or `...` statements), to test
-/// iterator behavior.
-///
 /// ## Example
 /// ```python
 /// import pytest
@@ -50,8 +50,6 @@ use super::helpers::is_empty_or_null_string;
 ///
 /// ## References
 /// - [`pytest` documentation: `pytest.raises`](https://docs.pytest.org/en/latest/reference/reference.html#pytest-raises)
-///
-/// [preview]: https://docs.astral.sh/ruff/preview/
 #[derive(ViolationMetadata)]
 pub(crate) struct PytestRaisesWithMultipleStatements;
 
@@ -206,14 +204,12 @@ pub(crate) fn complex_raises(checker: &Checker, stmt: &Stmt, items: &[WithItem],
     // Check body for `pytest.raises` context manager
     if raises_called {
         let is_too_complex = if let [stmt] = body {
-            let in_preview = checker.settings.preview.is_enabled();
-
             match stmt {
                 Stmt::With(ast::StmtWith { body, .. }) => is_non_trivial_with_body(body),
                 // Allow function and class definitions to test decorators.
                 Stmt::ClassDef(_) | Stmt::FunctionDef(_) => false,
                 // Allow empty `for` loops to test iterators.
-                Stmt::For(ast::StmtFor { body, .. }) if in_preview => match &body[..] {
+                Stmt::For(ast::StmtFor { body, .. }) => match &body[..] {
                     [Stmt::Pass(_)] => false,
                     [Stmt::Expr(ast::StmtExpr { value, .. })] => !value.is_ellipsis_literal_expr(),
                     _ => true,

crates/ruff_linter/src/rules/flake8_pytest_style/rules/warns.rs

@@ -13,6 +13,10 @@ use super::helpers::is_empty_or_null_string;
 /// ## What it does
 /// Checks for `pytest.warns` context managers with multiple statements.
 ///
+/// This rule allows `pytest.warns` bodies to contain `for`
+/// loops with empty bodies (e.g., `pass` or `...` statements), to test
+/// iterator behavior.
+///
 /// ## Why is this bad?
 /// When `pytest.warns` is used as a context manager and contains multiple
 /// statements, it can lead to the test passing when it should instead fail.
@@ -20,9 +24,6 @@ use super::helpers::is_empty_or_null_string;
 /// A `pytest.warns` context manager should only contain a single
 /// simple statement that triggers the expected warning.
 ///
-/// In [preview], this rule allows `pytest.warns` bodies to contain `for`
-/// loops with empty bodies (e.g., `pass` or `...` statements), to test
-/// iterator behavior.
 ///
 /// ## Example
 /// ```python
@@ -48,8 +49,6 @@ use super::helpers::is_empty_or_null_string;
 ///
 /// ## References
 /// - [`pytest` documentation: `pytest.warns`](https://docs.pytest.org/en/latest/reference/reference.html#pytest-warns)
-///
-/// [preview]: https://docs.astral.sh/ruff/preview/
 #[derive(ViolationMetadata)]
 pub(crate) struct PytestWarnsWithMultipleStatements;
 
@@ -206,14 +205,12 @@ pub(crate) fn complex_warns(checker: &Checker, stmt: &Stmt, items: &[WithItem],
     // Check body for `pytest.warns` context manager
     if warns_called {
         let is_too_complex = if let [stmt] = body {
-            let in_preview = checker.settings.preview.is_enabled();
-
             match stmt {
                 Stmt::With(ast::StmtWith { body, .. }) => is_non_trivial_with_body(body),
                 // Allow function and class definitions to test decorators.
                 Stmt::ClassDef(_) | Stmt::FunctionDef(_) => false,
                 // Allow empty `for` loops to test iterators.
-                Stmt::For(ast::StmtFor { body, .. }) if in_preview => match &body[..] {
+                Stmt::For(ast::StmtFor { body, .. }) => match &body[..] {
                     [Stmt::Pass(_)] => false,
                     [Stmt::Expr(ast::StmtExpr { value, .. })] => !value.is_ellipsis_literal_expr(),
                     _ => true,

crates/ruff_linter/src/rules/flake8_pytest_style/snapshots/ruff_linter__rules__flake8_pytest_style__tests__PT012.snap

@@ -124,49 +124,3 @@ PT012.py:95:5: PT012 `pytest.raises()` block should contain a single simple stat
 97 | |             assert foo
    | |______________________^ PT012
    |
-
-PT012.py:102:5: PT012 `pytest.raises()` block should contain a single simple statement
-    |
-100 |       ## No errors in preview
-101 |
-102 | /     with pytest.raises(RuntimeError):
-103 | |         for a in b:
-104 | |             pass
-    | |________________^ PT012
-105 |
-106 |       with pytest.raises(RuntimeError):
-    |
-
-PT012.py:106:5: PT012 `pytest.raises()` block should contain a single simple statement
-    |
-104 |               pass
-105 |
-106 | /     with pytest.raises(RuntimeError):
-107 | |         for a in b:
-108 | |             ...
-    | |_______________^ PT012
-109 |
-110 |       with pytest.raises(RuntimeError):
-    |
-
-PT012.py:110:5: PT012 `pytest.raises()` block should contain a single simple statement
-    |
-108 |               ...
-109 |
-110 | /     with pytest.raises(RuntimeError):
-111 | |         async for a in b:
-112 | |             pass
-    | |________________^ PT012
-113 |
-114 |       with pytest.raises(RuntimeError):
-    |
-
-PT012.py:114:5: PT012 `pytest.raises()` block should contain a single simple statement
-    |
-112 |               pass
-113 |
-114 | /     with pytest.raises(RuntimeError):
-115 | |         async for a in b:
-116 | |             ...
-    | |_______________^ PT012
-    |

crates/ruff_linter/src/rules/flake8_pytest_style/snapshots/ruff_linter__rules__flake8_pytest_style__tests__PT012_preview.snap

@@ -1,126 +0,0 @@
----
-source: crates/ruff_linter/src/rules/flake8_pytest_style/mod.rs
----
-PT012.py:42:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-41 |   def test_error_multiple_statements():
-42 | /     with pytest.raises(AttributeError):
-43 | |         len([])
-44 | |         [].size
-   | |_______________^ PT012
-   |
-
-PT012.py:48:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-47 |   async def test_error_complex_statement():
-48 | /     with pytest.raises(AttributeError):
-49 | |         if True:
-50 | |             [].size
-   | |___________________^ PT012
-51 |
-52 |       with pytest.raises(AttributeError):
-   |
-
-PT012.py:52:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-50 |               [].size
-51 |
-52 | /     with pytest.raises(AttributeError):
-53 | |         for i in []:
-54 | |             [].size
-   | |___________________^ PT012
-55 |
-56 |       with pytest.raises(AttributeError):
-   |
-
-PT012.py:56:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-54 |               [].size
-55 |
-56 | /     with pytest.raises(AttributeError):
-57 | |         async for i in []:
-58 | |             [].size
-   | |___________________^ PT012
-59 |
-60 |       with pytest.raises(AttributeError):
-   |
-
-PT012.py:60:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-58 |               [].size
-59 |
-60 | /     with pytest.raises(AttributeError):
-61 | |         while True:
-62 | |             [].size
-   | |___________________^ PT012
-63 |
-64 |       with pytest.raises(AttributeError):
-   |
-
-PT012.py:64:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-62 |               [].size
-63 |
-64 | /     with pytest.raises(AttributeError):
-65 | |         async with context_manager_under_test():
-66 | |             if True:
-67 | |                 raise Exception
-   | |_______________________________^ PT012
-   |
-
-PT012.py:71:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-70 |   def test_error_try():
-71 | /     with pytest.raises(AttributeError):
-72 | |         try:
-73 | |             [].size
-74 | |         except:
-75 | |             raise
-   | |_________________^ PT012
-   |
-
-PT012.py:83:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-81 |       ## Errors
-82 |
-83 | /     with pytest.raises(RuntimeError):
-84 | |         for a in b:
-85 | |             print()
-   | |___________________^ PT012
-86 |
-87 |       with pytest.raises(RuntimeError):
-   |
-
-PT012.py:87:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-85 |               print()
-86 |
-87 | /     with pytest.raises(RuntimeError):
-88 | |         for a in b:
-89 | |             assert foo
-   | |______________________^ PT012
-90 |
-91 |       with pytest.raises(RuntimeError):
-   |
-
-PT012.py:91:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-89 |               assert foo
-90 |
-91 | /     with pytest.raises(RuntimeError):
-92 | |         async for a in b:
-93 | |             print()
-   | |___________________^ PT012
-94 |
-95 |       with pytest.raises(RuntimeError):
-   |
-
-PT012.py:95:5: PT012 `pytest.raises()` block should contain a single simple statement
-   |
-93 |               print()
-94 |
-95 | /     with pytest.raises(RuntimeError):
-96 | |         async for a in b:
-97 | |             assert foo
-   | |______________________^ PT012
-   |

crates/ruff_linter/src/rules/flake8_pytest_style/snapshots/ruff_linter__rules__flake8_pytest_style__tests__PT031.snap

@@ -124,49 +124,3 @@ PT031.py:95:5: PT031 `pytest.warns()` block should contain a single simple state
 97 | |             assert foo
    | |______________________^ PT031
    |
-
-PT031.py:102:5: PT031 `pytest.warns()` block should contain a single simple statement
-    |
-100 |       ## No errors in preview
-101 |
-102 | /     with pytest.warns(RuntimeError):
-103 | |         for a in b:
-104 | |             pass
-    | |________________^ PT031
-105 |
-106 |       with pytest.warns(RuntimeError):
-    |
-
-PT031.py:106:5: PT031 `pytest.warns()` block should contain a single simple statement
-    |
-104 |               pass
-105 |
-106 | /     with pytest.warns(RuntimeError):
-107 | |         for a in b:
-108 | |             ...
-    | |_______________^ PT031
-109 |
-110 |       with pytest.warns(RuntimeError):
-    |
-
-PT031.py:110:5: PT031 `pytest.warns()` block should contain a single simple statement
-    |
-108 |               ...
-109 |
-110 | /     with pytest.warns(RuntimeError):
-111 | |         async for a in b:
-112 | |             pass
-    | |________________^ PT031
-113 |
-114 |       with pytest.warns(RuntimeError):
-    |
-
-PT031.py:114:5: PT031 `pytest.warns()` block should contain a single simple statement
-    |
-112 |               pass
-113 |
-114 | /     with pytest.warns(RuntimeError):
-115 | |         async for a in b:
-116 | |             ...
-    | |_______________^ PT031
-    |

crates/ruff_linter/src/rules/flake8_pytest_style/snapshots/ruff_linter__rules__flake8_pytest_style__tests__PT031_preview.snap

@@ -1,126 +0,0 @@
----
-source: crates/ruff_linter/src/rules/flake8_pytest_style/mod.rs
----
-PT031.py:42:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-41 |   def test_error_multiple_statements():
-42 | /     with pytest.warns(UserWarning):
-43 | |         foo()
-44 | |         bar()
-   | |_____________^ PT031
-   |
-
-PT031.py:48:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-47 |   async def test_error_complex_statement():
-48 | /     with pytest.warns(UserWarning):
-49 | |         if True:
-50 | |             foo()
-   | |_________________^ PT031
-51 |
-52 |       with pytest.warns(UserWarning):
-   |
-
-PT031.py:52:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-50 |               foo()
-51 |
-52 | /     with pytest.warns(UserWarning):
-53 | |         for i in []:
-54 | |             foo()
-   | |_________________^ PT031
-55 |
-56 |       with pytest.warns(UserWarning):
-   |
-
-PT031.py:56:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-54 |               foo()
-55 |
-56 | /     with pytest.warns(UserWarning):
-57 | |         async for i in []:
-58 | |             foo()
-   | |_________________^ PT031
-59 |
-60 |       with pytest.warns(UserWarning):
-   |
-
-PT031.py:60:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-58 |               foo()
-59 |
-60 | /     with pytest.warns(UserWarning):
-61 | |         while True:
-62 | |             foo()
-   | |_________________^ PT031
-63 |
-64 |       with pytest.warns(UserWarning):
-   |
-
-PT031.py:64:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-62 |               foo()
-63 |
-64 | /     with pytest.warns(UserWarning):
-65 | |         async with context_manager_under_test():
-66 | |             if True:
-67 | |                 foo()
-   | |_____________________^ PT031
-   |
-
-PT031.py:71:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-70 |   def test_error_try():
-71 | /     with pytest.warns(UserWarning):
-72 | |         try:
-73 | |             foo()
-74 | |         except:
-75 | |             raise
-   | |_________________^ PT031
-   |
-
-PT031.py:83:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-81 |       ## Errors
-82 |
-83 | /     with pytest.warns(RuntimeError):
-84 | |         for a in b:
-85 | |             print()
-   | |___________________^ PT031
-86 |
-87 |       with pytest.warns(RuntimeError):
-   |
-
-PT031.py:87:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-85 |               print()
-86 |
-87 | /     with pytest.warns(RuntimeError):
-88 | |         for a in b:
-89 | |             assert foo
-   | |______________________^ PT031
-90 |
-91 |       with pytest.warns(RuntimeError):
-   |
-
-PT031.py:91:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-89 |               assert foo
-90 |
-91 | /     with pytest.warns(RuntimeError):
-92 | |         async for a in b:
-93 | |             print()
-   | |___________________^ PT031
-94 |
-95 |       with pytest.warns(RuntimeError):
-   |
-
-PT031.py:95:5: PT031 `pytest.warns()` block should contain a single simple statement
-   |
-93 |               print()
-94 |
-95 | /     with pytest.warns(RuntimeError):
-96 | |         async for a in b:
-97 | |             assert foo
-   | |______________________^ PT031
-   |