Opaque datasets do not properly save when combined with attributes

[Blackclaws]

Two more problems I've encountered where I'm not sure whether it is a PureHDF or h5web problem:

var data = File.ReadAllBytes("/home/felix/screenshot.png");

var file = new H5File();
file["opaque"] = new H5Dataset(data, opaqueInfo: new H5OpaqueInfo((uint)data.Length, "test")); 

var opaqueGroup = new H5Group()
{
    Attributes =
    {
        {"Anything", "Data"}
    },
    ["stuff"] = new H5Group()
    {
     ["opaque"] = new H5Dataset(data, opaqueInfo: new H5OpaqueInfo((uint) data.Length, "test"))   
    }
};

file["group"] = opaqueGroup;

file.Write("testing.h5");

Writing this file (with a screenshot.png that is small enough that it doesn't directly break) one gets an error on opening the top group in h5web

testing.h5

group

stuff

opaque

opaque

group

Display

Inspect
HDF5-DIAG: Error detected in HDF5 (1.14.2) thread 0: #000: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5A.c line 1043 in H5Aread(): can't synchronously read data major: Attribute minor: Read failed #001: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5A.c line 1011 in H5A__read_api_common(): unable to read attribute major: Attribute minor: Read failed #002: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLcallback.c line 1236 in H5VL_attr_read(): attribute read failed major: Virtual Object Layer minor: Read failed #003: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLcallback.c line 1205 in H5VL__attr_read(): attribute read failed major: Virtual Object Layer minor: Read failed #004: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLnative_attr.c line 211 in H5VL__native_attr_read(): unable to read attribute major: Attribute minor: Read failed #005: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Aint.c line 754 in H5A__read(): datatype conversion failed major: Attribute minor: Unable to encode value #006: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5T.c line 5308 in H5T_convert(): datatype conversion failed major: Datatype minor: Can't convert datatypes #007: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Tconv.c line 3326 in H5T__conv_vlen(): can't read VL data major: Datatype minor: Read failed #008: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Tvlen.c line 840 in H5T__vlen_disk_read(): unable to get blob major: Datatype minor: Can't get value #009: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLcallback.c line 7396 in H5VL_blob_get(): blob get failed major: Virtual Object Layer minor: Can't get value #010: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLcallback.c line 7367 in H5VL__blob_get(): blob get callback failed major: Virtual Object Layer minor: Can't get value #011: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLnative_blob.c line 123 in H5VL__native_blob_get(): Expected global heap object size does not match major: Virtual Object Layer minor: Unable to decode value

When leaving out the top opaque dataset:

var data = File.ReadAllBytes("/home/felix/screenshot.png");

var file = new H5File();

var opaqueGroup = new H5Group()
{
    Attributes =
    {
        {"Anything", "Data"}
    },
    ["stuff"] = new H5Group()
    {
     ["opaque"] = new H5Dataset(data, opaqueInfo: new H5OpaqueInfo((uint) data.Length, "test"))   
    }
};

file["group"] = opaqueGroup;

file.Write("testing.h5");

The dataset does not get written as opaque instead it gets written as Integer (unsigned), 8-bit, little-endian

Originally posted by @Blackclaws in https://github.com/Apollo3zehn/PureHDF/issues/76#issuecomment-2077317439

[Blackclaws]

Even more simple:

var data = File.ReadAllBytes("/home/felix/screenshot.png");

var file = new H5File()
{
    Attributes =
    {
        {"Anything", "Data"}
    },
     ["opaque"] = new H5Dataset(data, opaqueInfo: new H5OpaqueInfo((uint) data.Length, "test"))   
};

file.Write("testing.h5");

Already shows the issue.

[Apollo3zehn]

Thanks, will be investigated later today :-)