[BUG] When blob contains no metadata then BlobItem.Metadata is null even if BlobTraits.Metadata was specified

[romanskrabis]

Describe the bug
When blob contains no metadata then BlobItem.Metadata is null even if BlobTraits.Metadata was specified for versions 12.5.1 or 12.6.0

Expected behavior
Metadata should be a dictionary with no items

Actual behavior (include Exception or Stack Trace)
Metadata is null

To Reproduce

        string connectionString = "";
        string containerName = "test-container";
        string blobName1 = "blob1";
        string blobName2 = "blob2";
        Dictionary<string, string> metadata1 = new Dictionary<string, string> { { "key", "value" } };
        Dictionary<string, string> metadata2 = new Dictionary<string, string> { };

        BlobContainerClient blobContainerClient = new BlobContainerClient(connectionString, containerName);
        blobContainerClient.CreateIfNotExists();

        BlockBlobClient blobClient1 = new BlockBlobClient(connectionString, containerName, blobName1);
        using (MemoryStream memoryStream1 = new MemoryStream(Encoding.ASCII.GetBytes("test")))
            blobClient1.Upload(memoryStream1, null, metadata1);

        BlockBlobClient blobClient2 = new BlockBlobClient(connectionString, containerName, blobName2);
        using (MemoryStream memoryStream2 = new MemoryStream(Encoding.ASCII.GetBytes("test")))
            blobClient2.Upload(memoryStream2, null, metadata2);


        Pageable<BlobItem> blobs = blobContainerClient.GetBlobs(BlobTraits.Metadata);
        BlobItem blob1 = blobs.FirstOrDefault(item => item.Name == blobName1);
        BlobItem blob2 = blobs.FirstOrDefault(item => item.Name == blobName2);

        // blob1.Metadata.Count is 1
        Console.WriteLine(blob1.Metadata?.Count);
        // blob2.Metadata.Count is 0 for Azure.Storage.Blobs version="12.4.4"
        // blob2.Metadata is null for Azure.Storage.Blobs version="12.5.1"
        Console.WriteLine(blob2.Metadata?.Count);

Environment:

• Worked as expected for Azure.Storage.Blobs version="12.4.4"
• Returns null for Azure.Storage.Blobs version="12.5.1"

[jsquire]

Thank you for your feedback. Tagging and routing to the team best able to assist.

[ghost]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @xgithubtriage.

[seanmcc-msft]

Hi @romisak, thanks for the detailed bug report. I'll look into getting this fixed in our next release.

-Sean