Limit isort.lines-after-imports to 1 for stub files (#9971)

crates/ruff_linter/resources/test/fixtures/isort/lines_after_imports.pyi

@@ -0,0 +1,16 @@
+from __future__ import annotations
+
+from typing import Any
+
+from requests import Session
+
+from my_first_party import my_first_party_object
+
+from . import my_local_folder_object
+
+
+
+class Thing(object):
+  name: str
+  def __init__(self, name: str):
+    self.name = name

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

@@ -108,7 +108,17 @@ pub(crate) fn format_imports(
         output.push_str(block_output.as_str());
     }
 
-    let lines_after_imports = settings.lines_after_imports;
+    let lines_after_imports = if source_type.is_stub() {
+        // Limit the number of lines after imports in stub files to at most 1 to be compatible with the formatter.
+        // `isort` does the same when using the profile `isort`
+        match settings.lines_after_imports {
+            0 => 0,
+            _ => 1,
+        }
+    } else {
+        settings.lines_after_imports
+    };
+
     match trailer {
         None => {}
         Some(Trailer::Sibling) => {
@@ -975,6 +985,7 @@ mod tests {
     }
 
     #[test_case(Path::new("lines_after_imports_nothing_after.py"))]
+    #[test_case(Path::new("lines_after_imports.pyi"))]
     #[test_case(Path::new("lines_after_imports_func_after.py"))]
     #[test_case(Path::new("lines_after_imports_class_after.py"))]
     fn lines_after_imports(path: &Path) -> Result<()> {
@@ -995,6 +1006,27 @@ mod tests {
         Ok(())
     }
 
+    #[test_case(Path::new("lines_after_imports.pyi"))]
+    #[test_case(Path::new("lines_after_imports_func_after.py"))]
+    #[test_case(Path::new("lines_after_imports_class_after.py"))]
+    fn lines_after_imports_default_settings(path: &Path) -> Result<()> {
+        let snapshot = path.to_string_lossy();
+        let mut diagnostics = test_path(
+            Path::new("isort").join(path).as_path(),
+            &LinterSettings {
+                src: vec![test_resource_path("fixtures/isort")],
+                isort: super::settings::Settings {
+                    lines_after_imports: -1,
+                    ..super::settings::Settings::default()
+                },
+                ..LinterSettings::for_rule(Rule::UnsortedImports)
+            },
+        )?;
+        diagnostics.sort_by_key(Ranged::start);
+        assert_messages!(*snapshot, diagnostics);
+        Ok(())
+    }
+
     #[test_case(Path::new("lines_between_types.py"))]
     fn lines_between_types(path: &Path) -> Result<()> {
         let snapshot = format!("lines_between_types{}", path.to_string_lossy());

crates/ruff_linter/src/rules/isort/snapshots/ruff_linter__rules__isort__tests__lines_after_imports.pyi.snap

@@ -0,0 +1,41 @@
+---
+source: crates/ruff_linter/src/rules/isort/mod.rs
+---
+lines_after_imports.pyi:1:1: I001 [*] Import block is un-sorted or un-formatted
+   |
+ 1 | / from __future__ import annotations
+ 2 | | 
+ 3 | | from typing import Any
+ 4 | | 
+ 5 | | from requests import Session
+ 6 | | 
+ 7 | | from my_first_party import my_first_party_object
+ 8 | | 
+ 9 | | from . import my_local_folder_object
+10 | | 
+11 | | 
+12 | | 
+13 | | class Thing(object):
+   | |_^ I001
+14 |     name: str
+15 |     def __init__(self, name: str):
+   |
+   = help: Organize imports
+
+ℹ Safe fix
+2  2  | 
+3  3  | from typing import Any
+4  4  | 
+5     |-from requests import Session
+6     |-
+7  5  | from my_first_party import my_first_party_object
+   6  |+from requests import Session
+8  7  | 
+9  8  | from . import my_local_folder_object
+10    |-
+11    |-
+12 9  | 
+13 10 | class Thing(object):
+14 11 |   name: str
+
+

crates/ruff_linter/src/rules/isort/snapshots/ruff_linter__rules__isort__tests__lines_after_imports_class_after.py.snap

@@ -0,0 +1,38 @@
+---
+source: crates/ruff_linter/src/rules/isort/mod.rs
+---
+lines_after_imports_class_after.py:1:1: I001 [*] Import block is un-sorted or un-formatted
+   |
+ 1 | / from __future__ import annotations
+ 2 | | 
+ 3 | | from typing import Any
+ 4 | | 
+ 5 | | from requests import Session
+ 6 | | 
+ 7 | | from my_first_party import my_first_party_object
+ 8 | | 
+ 9 | | from . import my_local_folder_object
+10 | | class Thing(object):
+   | |_^ I001
+11 |     name: str
+12 |     def __init__(self, name: str):
+   |
+   = help: Organize imports
+
+ℹ Safe fix
+2  2  | 
+3  3  | from typing import Any
+4  4  | 
+5     |-from requests import Session
+6     |-
+7  5  | from my_first_party import my_first_party_object
+   6  |+from requests import Session
+8  7  | 
+9  8  | from . import my_local_folder_object
+   9  |+
+   10 |+
+10 11 | class Thing(object):
+11 12 |   name: str
+12 13 |   def __init__(self, name: str):
+
+

crates/ruff_linter/src/rules/isort/snapshots/ruff_linter__rules__isort__tests__lines_after_imports_func_after.py.snap

@@ -0,0 +1,55 @@
+---
+source: crates/ruff_linter/src/rules/isort/mod.rs
+---
+lines_after_imports_func_after.py:1:1: I001 [*] Import block is un-sorted or un-formatted
+   |
+ 1 | / from __future__ import annotations
+ 2 | | 
+ 3 | | from typing import Any
+ 4 | | 
+ 5 | | from requests import Session
+ 6 | | 
+ 7 | | from my_first_party import my_first_party_object
+ 8 | | 
+ 9 | | from . import my_local_folder_object
+10 | | 
+11 | | 
+12 | | 
+13 | | 
+14 | | 
+15 | | 
+16 | | 
+17 | | 
+18 | | 
+19 | | 
+20 | | 
+21 | | def main():
+   | |_^ I001
+22 |     my_local_folder_object.get()
+   |
+   = help: Organize imports
+
+ℹ Safe fix
+2  2  | 
+3  3  | from typing import Any
+4  4  | 
+5     |-from requests import Session
+6     |-
+7  5  | from my_first_party import my_first_party_object
+   6  |+from requests import Session
+8  7  | 
+9  8  | from . import my_local_folder_object
+10    |-
+11    |-
+12    |-
+13    |-
+14    |-
+15    |-
+16    |-
+17    |-
+18    |-
+19 9  | 
+20 10 | 
+21 11 | def main():
+
+

crates/ruff_linter/src/rules/isort/snapshots/ruff_linter__rules__isort__tests__lines_after_imports_lines_after_imports.pyi.snap

@@ -0,0 +1,41 @@
+---
+source: crates/ruff_linter/src/rules/isort/mod.rs
+---
+lines_after_imports.pyi:1:1: I001 [*] Import block is un-sorted or un-formatted
+   |
+ 1 | / from __future__ import annotations
+ 2 | | 
+ 3 | | from typing import Any
+ 4 | | 
+ 5 | | from requests import Session
+ 6 | | 
+ 7 | | from my_first_party import my_first_party_object
+ 8 | | 
+ 9 | | from . import my_local_folder_object
+10 | | 
+11 | | 
+12 | | 
+13 | | class Thing(object):
+   | |_^ I001
+14 |     name: str
+15 |     def __init__(self, name: str):
+   |
+   = help: Organize imports
+
+ℹ Safe fix
+2  2  | 
+3  3  | from typing import Any
+4  4  | 
+5     |-from requests import Session
+6     |-
+7  5  | from my_first_party import my_first_party_object
+   6  |+from requests import Session
+8  7  | 
+9  8  | from . import my_local_folder_object
+10    |-
+11    |-
+12 9  | 
+13 10 | class Thing(object):
+14 11 |   name: str
+
+

crates/ruff_workspace/src/options.rs

@@ -2049,6 +2049,9 @@ pub struct IsortOptions {
     /// The number of blank lines to place after imports.
     /// Use `-1` for automatic determination.
     ///
+    /// Ruff uses at most one blank line after imports in typing stub files (files with `.pyi` extension) in accordance to
+    /// the typing style recommendations ([source](https://typing.readthedocs.io/en/latest/source/stubs.html#blank-lines)).
+    ///
     /// When using the formatter, only the values `-1`, `1`, and `2` are compatible because
     /// it enforces at least one empty and at most two empty lines after imports.
     #[option(