aws-sdk-go: service/s3: Metadata returns uppercase character

In the console:

screen shot 2015-11-18 at 11 21 56

When I do:

        result, err := c.HeadObject(&s3.HeadObjectInput{
            Bucket: aws.String("xxx"),
            Key:    aws.String("xxx"),
        })
        fmt.Printf("%#v\n", result)

I get:

...
{
  AcceptRanges: "bytes",
  ContentLength: 0,
  ContentType: "binary/octet-stream",
  ETag: "\"d41d8cd98f00b204e9800998ecf8427e\"",
  LastModified: 2015-11-18 19:00:42 +0000 UTC,
  Metadata: {
    Lp2: "87adaa3c-0bab-4808-a05b-cfe79ba23714"
  }
}
...

Please note Lp2. I would assume it returns lp2. Is this expected?

About this issue

Original URL
State: closed
Created 9 years ago
Reactions: 9
Comments: 17 (6 by maintainers)

Commits related to this issue

config: add document to LowerCaseHeaderMaps v1 vs v2 behavior (#4297) Adds small blurb to `Config.LowerCaseHeaderMaps` documenting the v1's opt-in behavior vs v2's default behavior. Related to #445 — committed to aws/aws-sdk-go by jasdel 2 years ago

Most upvoted comments

Please note that this issue still persists more than two years after it was originally opened. I would consider this a bug rather than a Feature Request - different casing is unexpected behavior and requires additional code as a workaround.

MasterCarl on Feb 5, 2018

Hi, guys. Actually, you can use LowerCaseHeaderMaps to do this trick now. From the aws/config.go:

// Set this to `true` to enable the SDK to unmarshal API response header maps to
// normalized lower case map keys.
//
// For example S3's X-Amz-Meta prefixed header will be unmarshaled to lower case
// Metadata member's map keys. The value of the header in the map is unaffected.
LowerCaseHeaderMaps *bool

But there was a bug in this feature, and the PR #3671 fixed this.

Amazon metadata for S3 is case insensitive on the keys, but the Golang SDK is weird. The unmarshalHeaderMap method always returns the canonical header key form. So enable LowerCaseHeaderMaps config will return the lower case key form. You can check this test private/protocol/rest/rest_test.go to see how it works.

Cheers.

bkda on Feb 23, 2021

Ping.

graywolf-at-work on Feb 24, 2022

This is definitely a bug, not a feature-request. Still there in 1.29.21.

What makes it even more confusing is that if you set the metadata for example via PutObjectInput the keys will always be set as all lowercase.

kerma on Apr 8, 2020

still an issue with v1.20.2 😦

pwmcintyre on Jun 18, 2019

the problem still not solved, using version: v1.16.26 😕

NeoyeElf on Jan 29, 2019

@mattes The SDK will automatically case the metadata fields to Go net/http’s standard header canonical formating. The issue we’re seeing here is the service’s implementation details of the metadata fields being transmitted via headers bleeding into how the SDK returns them.

This issue could be addressed and maintain backwards compatibility by introducing an option to ensure the metadata parameters maintain their original casing. Instead of using Go’s canonical header key format.

jasdel on Jan 7, 2016