From 24bab7e82e59bb4940cf383c4f393de6e024e80d Mon Sep 17 00:00:00 2001
From: Vasco Schiavo <115561717+VascoSch92@users.noreply.github.com>
Date: Thu, 6 Feb 2025 08:51:51 +0100
Subject: [PATCH] [pycodestyle] Exempt `sys.path += ...` calls (E402) (#15980)

## Summary

The PR addresses issue #15886 .
---
 .../test/fixtures/pycodestyle/E402_4.py       |  7 +++
 .../ruff_linter/src/rules/pycodestyle/mod.rs  |  1 +
 ...s__pycodestyle__tests__E402_E402_4.py.snap |  3 ++
 .../src/analyze/imports.rs                    | 54 ++++++++++---------
 4 files changed, 40 insertions(+), 25 deletions(-)
 create mode 100644 crates/ruff_linter/resources/test/fixtures/pycodestyle/E402_4.py
 create mode 100644 crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E402_E402_4.py.snap

diff --git a/crates/ruff_linter/resources/test/fixtures/pycodestyle/E402_4.py b/crates/ruff_linter/resources/test/fixtures/pycodestyle/E402_4.py
new file mode 100644
index 0000000000..7bcc01f89b
--- /dev/null
+++ b/crates/ruff_linter/resources/test/fixtures/pycodestyle/E402_4.py
@@ -0,0 +1,7 @@
+import os
+import sys
+
+sys.path += [os.path.dirname(__file__)]
+sys.path += ["../"]
+
+from package import module
\ No newline at end of file
diff --git a/crates/ruff_linter/src/rules/pycodestyle/mod.rs b/crates/ruff_linter/src/rules/pycodestyle/mod.rs
index 9c55fedb07..84b3363f10 100644
--- a/crates/ruff_linter/src/rules/pycodestyle/mod.rs
+++ b/crates/ruff_linter/src/rules/pycodestyle/mod.rs
@@ -44,6 +44,7 @@ mod tests {
     #[test_case(Rule::ModuleImportNotAtTopOfFile, Path::new("E402_1.py"))]
     #[test_case(Rule::ModuleImportNotAtTopOfFile, Path::new("E402_2.py"))]
     #[test_case(Rule::ModuleImportNotAtTopOfFile, Path::new("E402_3.py"))]
+    #[test_case(Rule::ModuleImportNotAtTopOfFile, Path::new("E402_4.py"))]
     #[test_case(Rule::ModuleImportNotAtTopOfFile, Path::new("E402.ipynb"))]
     #[test_case(Rule::MultipleImportsOnOneLine, Path::new("E40.py"))]
     #[test_case(Rule::MultipleStatementsOnOneLineColon, Path::new("E70.py"))]
diff --git a/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E402_E402_4.py.snap b/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E402_E402_4.py.snap
new file mode 100644
index 0000000000..195339b453
--- /dev/null
+++ b/crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E402_E402_4.py.snap
@@ -0,0 +1,3 @@
+---
+source: crates/ruff_linter/src/rules/pycodestyle/mod.rs
+---
diff --git a/crates/ruff_python_semantic/src/analyze/imports.rs b/crates/ruff_python_semantic/src/analyze/imports.rs
index a88103693b..19802a8092 100644
--- a/crates/ruff_python_semantic/src/analyze/imports.rs
+++ b/crates/ruff_python_semantic/src/analyze/imports.rs
@@ -8,33 +8,37 @@ use crate::SemanticModel;
 /// import sys
 ///
 /// sys.path.append("../")
+/// sys.path += ["../"]
 /// ```
 pub fn is_sys_path_modification(stmt: &Stmt, semantic: &SemanticModel) -> bool {
-    let Stmt::Expr(ast::StmtExpr { value, range: _ }) = stmt else {
-        return false;
-    };
-    let Expr::Call(ast::ExprCall { func, .. }) = value.as_ref() else {
-        return false;
-    };
-    semantic
-        .resolve_qualified_name(func.as_ref())
-        .is_some_and(|qualified_name| {
-            matches!(
-                qualified_name.segments(),
-                [
-                    "sys",
-                    "path",
-                    "append"
-                        | "insert"
-                        | "extend"
-                        | "remove"
-                        | "pop"
-                        | "clear"
-                        | "reverse"
-                        | "sort"
-                ]
-            )
-        })
+    match stmt {
+        Stmt::Expr(ast::StmtExpr { value, range: _ }) => match value.as_ref() {
+            Expr::Call(ast::ExprCall { func, .. }) => semantic
+                .resolve_qualified_name(func.as_ref())
+                .is_some_and(|qualified_name| {
+                    matches!(
+                        qualified_name.segments(),
+                        [
+                            "sys",
+                            "path",
+                            "append"
+                                | "insert"
+                                | "extend"
+                                | "remove"
+                                | "pop"
+                                | "clear"
+                                | "reverse"
+                                | "sort"
+                        ]
+                    )
+                }),
+            _ => false,
+        },
+        Stmt::AugAssign(ast::StmtAugAssign { target, .. }) => semantic
+            .resolve_qualified_name(map_subscript(target))
+            .is_some_and(|qualified_name| matches!(qualified_name.segments(), ["sys", "path"])),
+        _ => false,
+    }
 }
 
 /// Returns `true` if a [`Stmt`] is an `os.environ` modification, as in: