S3 Metadata Keys are modified when returned.

[beiriannydd]

Please fill out the sections below to help us address your issue.

Version of AWS SDK for Go?

v1.15.38

Version of Go (go version)?

1.10

What issue did you see?

Metadata returned from S3 objects has LeadingCapital conversion of keys

Steps to reproduce

Partial Example

md := map[string]*string {
  "example": AWSString("not Example"),
}
poi := &s3.PutObjectInput{
  Body: aws.ReadSeekCloser(source),
  Bucket: aws.String(bucket),
  Key: aws.String(key),
  Metadata: md,
  }
svc.PutObject(poi)
hoi := &s3.HeadObjectInput{
  Bucket: aws.String(bucket),
  Key:    aws.String(key),
}
result, _ := svc.HeadObject(hoi)
assert.Equal(reflect.DeepEqual(md, result.Metadata),true) // fails assertion

This fails because in result, the key is named "Example". I couldn't find documentation for this behavior and it is also surprising. If Example and example are given as keys then the result is the two values joined by ',' which makes sense, I suppose. I then tested "example_eg" and "ExampleEg" which generated two different keys, which further surprised. If you're going to modify the case to lower, why not use a method which has a way back to the original?

[beiriannydd]

Ah #445

[beiriannydd]

How would you feel about implementing an aws.Canon(s string) function to be used when generating Metadata in order to generate it in the same format as would be returned by the methods? That way the programmer can use the names they're familiar with and leave it to the library to ensure that the metadata is comparable? Basically it would return textproto.CanonicalMIMEHeaderKey(s). The important piece would be using this function everywhere metadata keys are used in examples and documentation.

[diehlaws]

Hi @beiriannydd, thanks or your feedback on this topic. In order to maintain organized discussions on issues we encourage commenting on existing issues rather than re-initiating the discussion on a new issue. I am closing this issue as a duplicate, however your feedback has been included in the internal discussion for the implementation of this feature.