S3Path does not set object mime-type when uploading a file on S3

[davidatsamp]

In order to serve correctly S3 object from cloudfront origin, we need to set correctly S3 object mime-type.
Unfortunately the S3 client does not provide any mime-type when calling upload_file.

It could be possible to use at least the mimetypes module for the most common mime-types based on file extension in s3client.py:

def _upload_file(self, local_path: Union[str, os.PathLike], cloud_path: S3Path) -> S3Path:
    obj = self.s3.Object(cloud_path.bucket, cloud_path.key)

    extra_args = {}
    content_type, content_encoding = mimetypes.guess_type(str(local_path))
    if content_type is not None:
        extra_args["ContentType"] = content_type
    if content_encoding is not None:
        extra_args["ContentEncoding"] = content_encoding

    obj.upload_file(str(local_path), Config=self.boto3_transfer_config, ExtraArgs=extra_args)
    return cloud_path

[pjbull]

I agree it would be good to support content types—especially for web publishing flows. Maybe we can use an implementation like the above and have a guess_mimetypes flag that is set in the client __init__ so people can disable this behavior if it is doing unexpected things.

Two notes:

• Default on or off may depend on mimetypes.guess_type performance.
• We may want to think about a better way to let users explicitly set this per-file, (e.g., setters for certain properties), but I like this as a low-lift immediate implementation.

[davidatsamp]

An alternate solution could be to set globally a mime type / content encoding function provider. So the default implementation could be mimetypes.guess_type and it would be easy to provide an alternate implementation if needed.
Something like that:
S3Path.mimetype_guess = my_own_mimetype_guess_function
I think about a global setup because it should be a real pain (and error prone) to have to set this configuration on a per instance basis.

[pjbull]

I think about a global setup because it should be a real pain (and error prone) to have to set this configuration on a per instance basis.

Agreed this should not need to be set per CloudPath object. If you wanted to use something other than the defaults, you would either create a specific client and then use that client's factory methods to create all the path instances, or you would create the client and then call set_as_default_client so that it was automatically used for all future instances.

You can see examples of those two patterns in the docs here:
https://cloudpathlib.drivendata.org/stable/authentication/#advanced-use

Either way, though, you'd only have to set it in one place.

[pjbull]

@davidatsamp this should be fixed in 0.8.0 which is on pypi now. could you test your use case and confirm? guess_type is the default and instructions for customizing are here: https://cloudpathlib.drivendata.org/stable/other_client_settings/#content-type-guessing-content_type_method

[davidatsamp]

I have tested it and integrate it. Thanks a lot 👍