Merge branch 'fix/p1-vds' into fix/p1-read-gaps

# Conflicts:
#	CHANGELOG.md
#	crates/clawhdf5-format/src/data_read.rs

crates/clawhdf5-format/tests/integration_test.rs

@@ -83,6 +83,45 @@ fn read_chunked_dataset(file_data: &[u8], dataset_path: &str) -> (Vec<u8>, Datat
     (raw, datatype, dataspace)
 }
 
+/// Helper: read a virtual dataset with `vds::read_virtual_dataset`, giving it
+/// the dataset's own fill value (same-file sources only).
+fn read_virtual_fixture(file_data: &[u8], path: &str) -> (Vec<u8>, Datatype) {
+    let sig = find_signature(file_data).unwrap();
+    let sb = Superblock::parse(file_data, sig).unwrap();
+    let addr = resolve_path_any(file_data, &sb, path).unwrap();
+    let hdr =
+        ObjectHeader::parse(file_data, addr as usize, sb.offset_size, sb.length_size).unwrap();
+    let msg = |t: MessageType| hdr.messages.iter().find(|m| m.msg_type == t).unwrap();
+    let ds = Dataspace::parse(&msg(MessageType::Dataspace).data, sb.length_size).unwrap();
+    let (dt, _) = Datatype::parse(&msg(MessageType::Datatype).data).unwrap();
+    let layout = DataLayout::parse(
+        &msg(MessageType::DataLayout).data,
+        sb.offset_size,
+        sb.length_size,
+    )
+    .unwrap();
+    let fill = clawhdf5_format::fill_value::dataset_fill_value_in(
+        file_data,
+        &hdr.messages,
+        sb.offset_size,
+        sb.length_size,
+    )
+    .unwrap();
+    let v = clawhdf5_format::vds::read_virtual_dataset(
+        file_data,
+        &layout,
+        &ds,
+        &dt,
+        fill.as_deref(),
+        sb.offset_size,
+        sb.length_size,
+        None,
+    )
+    .unwrap();
+    assert_eq!(v.dims, ds.dimensions);
+    (v.data, dt)
+}
+
 /// Helper: read any dataset (contiguous or chunked) as f64.
 fn read_dataset_f64_any(bytes: &[u8], path: &str) -> Vec<f64> {
     let sig = find_signature(bytes).unwrap();
@@ -672,7 +711,7 @@ fn v4_virtual_dataset_same_file_read() {
     //   virt[4:8]  <- (unmapped)                              => fill 0
     //   virt[8:12] <- src_b[0:4]  (ALL)                       => 20,21,22,23
     let file_data = include_bytes!("fixtures/vds_same_file.h5");
-    let (raw, datatype, _) = read_chunked_dataset(file_data, "virt");
+    let (raw, datatype) = read_virtual_fixture(file_data, "virt");
     let values = read_as_i32(&raw, &datatype).unwrap();
     assert_eq!(
         values,
@@ -681,6 +720,38 @@ fn v4_virtual_dataset_same_file_read() {
     );
 }
 
+#[test]
+fn v4_virtual_dataset_raw_api_refuses_to_guess_the_fill_value() {
+    // The raw read API has no fill value message, so a virtual dataset with an
+    // unmapped region is an error there instead of zeros that may be wrong.
+    let file_data = include_bytes!("fixtures/vds_same_file.h5");
+    let sig = find_signature(file_data).unwrap();
+    let sb = Superblock::parse(file_data, sig).unwrap();
+    let addr = resolve_path_any(file_data, &sb, "virt").unwrap();
+    let hdr =
+        ObjectHeader::parse(file_data, addr as usize, sb.offset_size, sb.length_size).unwrap();
+    let msg = |t: MessageType| hdr.messages.iter().find(|m| m.msg_type == t).unwrap();
+    let ds = Dataspace::parse(&msg(MessageType::Dataspace).data, sb.length_size).unwrap();
+    let (dt, _) = Datatype::parse(&msg(MessageType::Datatype).data).unwrap();
+    let layout = DataLayout::parse(
+        &msg(MessageType::DataLayout).data,
+        sb.offset_size,
+        sb.length_size,
+    )
+    .unwrap();
+    let err = read_raw_data_full(
+        file_data,
+        &layout,
+        &ds,
+        &dt,
+        None,
+        sb.offset_size,
+        sb.length_size,
+    )
+    .unwrap_err();
+    assert!(err.to_string().contains("fill value"), "{err}");
+}
+
 #[test]
 fn v4_virtual_dataset_2d_same_file_read() {
     // A 4x4 virtual dataset assembled from two 2x2 same-file sources placed as
@@ -689,7 +760,7 @@ fn v4_virtual_dataset_2d_same_file_read() {
     //   virt[2:4,2:4] <- src_b = [[5,6],[7,8]]
     //   everything else -> fill 0
     let file_data = include_bytes!("fixtures/vds_2d_same_file.h5");
-    let (raw, datatype, _) = read_chunked_dataset(file_data, "virt");
+    let (raw, datatype) = read_virtual_fixture(file_data, "virt");
     let values = read_as_i32(&raw, &datatype).unwrap();
     assert_eq!(
         values,