Fix str.zfill() width calculation for non-ASCII strings (RustPython#7534)

Copilot · web-flow · commit eed618d85886 · 2026-04-04T14:45:30.000+09:00
diff --git a/crates/vm/src/anystr.rs b/crates/vm/src/anystr.rs
@@ -396,6 +396,10 @@ pub trait AnyStr {
 
     fn py_zfill(&self, width: isize) -> Vec<u8> {
         let width = width.to_usize().unwrap_or(0);
+        let char_len = self.elements().count();
+        let width = self
+            .bytes_len()
+            .saturating_add(width.saturating_sub(char_len));
         rustpython_common::str::zfill(self.as_bytes(), width)
     }
 
diff --git a/extra_tests/snippets/builtin_str.py b/extra_tests/snippets/builtin_str.py
@@ -61,6 +61,9 @@
 assert not a.endswith("on")
 assert not a.endswith(("A", "ll"))
 assert a.zfill(8) == "000Hallo"
+assert "á".zfill(4) == "000á"
+assert "🙂".zfill(5) == "0000🙂"
+assert "+あ".zfill(5) == "+000あ"
 assert a.isalnum()
 assert not a.isdigit()
 assert not a.isdecimal()

Original file line number	Diff line number	Diff line change
`@@ -396,6 +396,10 @@ pub trait AnyStr {`
`396`	`396`
`397`	`397`	`fn py_zfill(&self, width: isize) -> Vec<u8> {`
`398`	`398`	`let width = width.to_usize().unwrap_or(0);`
	`399`	`+ let char_len = self.elements().count();`
	`400`	`+ let width = self`
	`401`	`+ .bytes_len()`
	`402`	`+ .saturating_add(width.saturating_sub(char_len));`
`399`	`403`	`rustpython_common::str::zfill(self.as_bytes(), width)`
`400`	`404`	`}`
`401`	`405`