S3 Client not Exposing HeadBucket

[dscpinheiro]

Discussed in #3175

^{Originally posted by omamoo February 7, 2024}
Hello all,

I'm writing a code that uploading content to S3 bucket that resides at different account, i.e. I have a cross account scenario of uploading content to S3.

While writing the code I used GetBucketLocation API call to determine the bucket location, however on cross account scenario the GetBucketLocation fails since I'm not the bucket owner, in addition, I saw on AWS documentation that their recommendation is to use HeadBucket API call, however the SDK does not expose this API call and defined this call as internal.

Here is a snapshot from the SDK code:

internal virtual Task<HeadBucketResponse> HeadBucketAsync(HeadBucketRequest request, System.Threading.CancellationToken cancellationToken = default(CancellationToken))
        {
            var options = new InvokeOptions();
            options.RequestMarshaller = HeadBucketRequestMarshaller.Instance;
            options.ResponseUnmarshaller = HeadBucketResponseUnmarshaller.Instance;

            return InvokeAsync<HeadBucketResponse>(request, options, cancellationToken);
        }

Can we make this public for use?

[b-dongen]

In case anyone is inpatient like me, I've created this extension method using reflection to access the HeadBucketAsync() method.

static class AmazonS3ClientExtension
{
#pragma warning disable S3011 // Reflection should not be used to increase accessibility of classes, methods, or fields
    static readonly MethodInfo _headBucketAsyncMethod = typeof(AmazonS3Client)
        .GetMethod("HeadBucketAsync", BindingFlags.Instance | BindingFlags.NonPublic)!;
    static readonly FieldInfo _httpClientResponseDataHeaderField = typeof(HttpClientResponseData)
        .GetField("_headers", BindingFlags.NonPublic | BindingFlags.Instance)!;
#pragma warning restore S3011 // Reflection should not be used to increase accessibility of classes, methods, or fields

    static public Task<HeadBucketResponse> HeadBucketAsync(this AmazonS3Client client, HeadBucketRequest request, CancellationToken cancellationToken = default)
        => (Task<HeadBucketResponse>)_headBucketAsyncMethod.Invoke(client, [request, cancellationToken])!;

    // Use reflection to get the region from the response-headers
    static public string? GetRegionFromResponseHeader(this AmazonServiceException ex)
    {
        var responseEx = ex.InnerException as HttpErrorResponseException;
        var responseData = responseEx?.Response as HttpClientResponseData;
        var headers = _httpClientResponseDataHeaderField.GetValue(responseData) as Dictionary<string, string>;
        string? region = headers?.GetValueOrDefault("x-amz-bucket-region");

        return region;
    }
}

[ashishdhingra]

PR #3712 merged to main-staging after today's daily release. The change would go out in tomorrow's daily release.

[ashishdhingra]

Changes released in AWSSDK.S3 version 3.7.415.23.

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