[pyupgrade] Fix false positive on relative imports from local .builtins module (UP029) (#21309)

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP029_2.py

@@ -0,0 +1,5 @@
+from .builtins import next
+from ..builtins import str
+from ...builtins import int
+from .builtins import next as _next
+

crates/ruff_linter/src/checkers/ast/analyze/statement.rs

@@ -717,7 +717,9 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
             }
             if checker.is_rule_enabled(Rule::UnnecessaryBuiltinImport) {
                 if let Some(module) = module {
-                    pyupgrade::rules::unnecessary_builtin_import(checker, stmt, module, names);
+                    pyupgrade::rules::unnecessary_builtin_import(
+                        checker, stmt, module, names, level,
+                    );
                 }
             }
             if checker.any_rule_enabled(&[

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

@@ -99,6 +99,7 @@ mod tests {
     #[test_case(Rule::UTF8EncodingDeclaration, Path::new("UP009_many_empty_lines.py"))]
     #[test_case(Rule::UnicodeKindPrefix, Path::new("UP025.py"))]
     #[test_case(Rule::UnnecessaryBuiltinImport, Path::new("UP029_0.py"))]
+    #[test_case(Rule::UnnecessaryBuiltinImport, Path::new("UP029_2.py"))]
     #[test_case(Rule::UnnecessaryClassParentheses, Path::new("UP039.py"))]
     #[test_case(Rule::UnnecessaryDefaultTypeArgs, Path::new("UP043.py"))]
     #[test_case(Rule::UnnecessaryEncodeUTF8, Path::new("UP012.py"))]

crates/ruff_linter/src/rules/pyupgrade/rules/unnecessary_builtin_import.rs

@@ -75,7 +75,13 @@ pub(crate) fn unnecessary_builtin_import(
     stmt: &Stmt,
     module: &str,
     names: &[Alias],
+    level: u32,
 ) {
+    // Ignore relative imports (they're importing from local modules, not Python's builtins).
+    if level > 0 {
+        return;
+    }
+
     // Ignore irrelevant modules.
     if !matches!(
         module,

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP029_2.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff_linter/src/rules/pyupgrade/mod.rs
+---
+