fix(format): a group attribute set again replaces the earlier value

Setting a group or root attribute twice wrote two attribute messages with the same name, and h5py read back the first value: set_attr("w", 1) then set_attr("w", "two") read as 1. The later value now replaces the earlier one, as `attrs[name] = v` does in h5py, including when a group is merged from two builders. Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
2026-09-26 08:35:16 -05:00
parent bd36fe883b
commit b0a1e4f9a6
3 changed files with 39 additions and 6 deletions
@@ -610,3 +610,31 @@ fn non_ascii_names_are_utf8() {
    let f = File::open(&path).unwrap();
    assert_eq!(f.dataset("größe/wert").unwrap().read_i32().unwrap(), [1]);
 }
+
+#[test]
+fn a_group_attribute_set_again_takes_the_new_value() {
+    skip_if_no_python!();
+    // Setting a group attribute twice wrote two attribute messages with one
+    // name. Now the later value replaces the earlier, as `attrs[name] = v`
+    // does in h5py — also across a group merged from two builders.
+    let dir = tempfile::tempdir().unwrap();
+    let mut b = FileBuilder::new();
+    b.set_attr("v", AttrValue::I64(1));
+    b.set_attr("v", AttrValue::I64(2));
+    let mut g = b.create_group("g");
+    g.set_attr("w", AttrValue::I64(1));
+    b.add_group(g.finish());
+    let mut g = b.create_group("g");
+    g.set_attr("w", AttrValue::String("two".into()));
+    b.add_group(g.finish());
+    let path = write(&dir, "attrs.h5", b);
+    let out = h5py(
+        &path,
+        "with h5py.File(path, 'r') as f:\n\
+         \x20   print(json.dumps([list(f.attrs), int(f.attrs['v']), list(f['g'].attrs),\n\
+         \x20       f['g'].attrs['w'].decode()]))",
+    );
+    assert_eq!(out, r#"[["v"], 2, ["w"], "two"]"#);
+    let f = File::open(&path).unwrap();
+    assert!(matches!(f.root().attrs().unwrap()["v"], AttrValue::I64(2)));
+}