aws s3 cp errors when "-" stream to stdout option is used with a prefix

[davidwarshaw]

aws-cli/1.10.1 Python/2.7.6 Darwin/14.3.0 botocore/1.3.23

When used with a prefix, "-" stream to stdout option errors with a 404, with or without --recursive flag.

> aws s3 ls s3://my-bucket/my-prefix --recursive
my-prefix/_SUCCESS
my-prefix/part-00000
my-prefix/part-00001
...

> aws s3 cp s3://my-bucket/my-prefix/part-00000 -
My data row 1
My data row 2
My data row 3
...

> aws s3 cp s3://my-bucket/my-prefix -
A client error (404) occurred when calling the HeadObject operation: Not Found

> aws s3 cp s3://my-bucket/my-prefix - --recursive
A client error (404) occurred when calling the HeadObject operation: Not Found

If this use of the option is not allowed, perhaps the documentation should be updated to reflect.

[jamesls]

The first case:

> aws s3 cp s3://my-bucket/my-prefix -
A client error (404) occurred when calling the HeadObject operation: Not Found

doesn't seem like the CLI can really do much with that. We interpret that as you wanting to download the s3://mybucket/my-prefix key to stdout. We have no way of knowing that you meant a prefix. It's the same situation if you have aws s3 cp s3://bucket/somekey /tmp/myfile. We assume you want to download the somekey file to /tmp/myfile.

The second case with the --recursive option on the other hand, seems like something we should be able to validate. If you want to stream to stdout, then --recursive should not be allowed and we should error out.

[davidwarshaw]

I agree with the reasoning to leave behavior as is for the case without --recursive.

When --recursive is used, I would have expected the behavior to be idiomatic with the other options and commands. Traverse the prefix in whatever the normal order is, streaming each key to stdout.

Barring this, I agree with erroring out at argument parsing with a good message, and adding a line to the docs for each option, specifying that they can't be used together.