Aws-sdk-js: Better documentation for AWS.S3.copyObject on updating ContentType

[yvele]

http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#copyObject-property

Updating ContentType is so confusing as it requires to pass MetadataDirective to REPLACE

I lost a lot of time to figure out why passing ContentType alone doesn't have any effect.
I find out how to do with this answer : https://github.com/aws/aws-sdk-php/issues/717#issuecomment-165298178

I think the doc (not only JavaScriptSDK) should say that ContentType is considered as a metadata and not a simple header.

Summary :

• There is a Metadata, a ContentType and a MetadataDirective field
• If I only pass a ContentType nothing appends.. Not even an error
• Even I don't pass Metadata, I have to pass MetadataDirective in order to update ContentType
• ContentType update does not have the same behaviour as other header (eg ContentEncoding)

[denisw]

For reference, this is a copyObject call that changes the content type of an object:

s3.copyObject({
  Bucket: bucket,
  Key: key,
  CopySource: `${bucket}/${key}`,
  ContentType: newContentType,
  MetadataDirective: 'REPLACE'
})

[jlumia]

@denisw

Thank you. The MetadataDirective worked perfectly!

[ArthurRM]

Similarly it is equally confusing when you just want to update the metadata and thus pass MetadataDirective = REPLACE but then you lose the original ContentType if you don't explicitly set that in the copy again as well.

[arnulfojr]

Would be amazing if the docs could be updated to mention what happens if the MetadataDirective is not present and what's the default value? I think is ok as is, just more clear docs would be appreciated :+1:

[bobbles911]

+1, I lost a couple of hours wondering why Content-Disposition was not getting applied. It's been three years, come on

[allison-vb]

+1

[clintfoster]

On the broader topic of updating metadata efficiently without rewriting the object content, I'm looking at this again after a couple of years, and I see there is no information in the S3 User's Guide or the detailed JavaDoc about this seemingly obvious use case. Am I missing something?

Doing a Google search returns a tremendous amount of lore and speculation for the Java and Boto client SDKs covering a period of several years, none of which seems definitive.

[bozerkins]

+1

[shakhal]

+1