Allow string percent formatting in os.getenv (#3518)

crates/ruff/resources/test/fixtures/pylint/invalid_envvar_default.py

@@ -8,5 +8,5 @@ os.getenv("AA", "GOOD")
 os.getenv("AA", f"GOOD")
 os.getenv("AA", "GOOD" + "BAD")
 os.getenv("AA", "GOOD" + 1)
+os.getenv("AA", "GOOD %s" % "BAD")
 os.getenv("B", Z)
-

crates/ruff/src/rules/pylint/rules/invalid_envvar_default.rs

@@ -49,6 +49,7 @@ fn is_valid_default(expr: &Expr) -> bool {
         return true;
     }
 
+    // Allow string concatenation.
     if let ExprKind::BinOp {
         left,
         right,
@@ -58,6 +59,16 @@ fn is_valid_default(expr: &Expr) -> bool {
         return is_valid_default(left) && is_valid_default(right);
     }
 
+    // Allow string formatting.
+    if let ExprKind::BinOp {
+        left,
+        op: Operator::Mod,
+        ..
+    } = &expr.node
+    {
+        return is_valid_default(left);
+    }
+
     // Otherwise, the default must be a string or `None`.
     matches!(
         expr.node,

crates/ruff/src/rules/pylint/rules/invalid_envvar_value.rs

@@ -46,6 +46,7 @@ fn is_valid_key(expr: &Expr) -> bool {
         return true;
     }
 
+    // Allow string concatenation.
     if let ExprKind::BinOp {
         left,
         right,
@@ -55,6 +56,16 @@ fn is_valid_key(expr: &Expr) -> bool {
         return is_valid_key(left) && is_valid_key(right);
     }
 
+    // Allow string formatting.
+    if let ExprKind::BinOp {
+        left,
+        op: Operator::Mod,
+        ..
+    } = &expr.node
+    {
+        return is_valid_key(left);
+    }
+
     // Otherwise, the default must be a string.
     matches!(
         expr.node,