[Bug]: swift AssumeRole example gives missing region authError

[ramink]

Expected behavior

I expected to either get a list of S3 buckets, or to get some sort of authentication error.

Actual behavior

The program errored out, because of a "Missing region in auth scheme parameters for SigV4 auth scheme."

Steps to reproduce

1. cloned examples repo
2. cd <repo>/swift/example_code/sts/AssumeRole
3. swift run AssumeRole arn:anything_here_the_arn_seems_not_to_matter
4. I also tried with CL options for access-key, secret-key, and even session-token associated with a real ARN, but got the same result.

Also, sorry, I can't tell what version of the SDK gets pulled by the `swift run` command.

Logs / stacktrace (if applicable)

▿ Smithy.ClientError.authError
  - authError: "Missing region in auth scheme parameters for SigV4 auth scheme."
ERROR: Error assuming role in runAsync: authError("Missing region in auth scheme parameters for SigV4 auth scheme.")
Error: assumeRoleFailed

Which SDK were you using?

Swift

Which OS were you using?

macOS

SDK version

latest

OS version

macOS Sequoia 15.0.1

[ramink]

I figured out a way to remove the error. I had to append , region: "us-west-2" to line 150 of Source/entry.swift. But this seems contrary to my understanding of how STS works - that you should be able to work at the global level. I don't know. I'm just starting and perhaps am getting various ideas muddled up.

[cpyle0819]

Hey @ramink . I'm assigning this to the writer who created it.

[shepazon]

Yeah, the example is reliant upon your AWS login having a region associated with it, such as by setting the environment variable AWS_REGION. This is to prevent the example from using a region distant from the user for the purposes of the example. The best solution would be for the example to allow a --region option on the command line to set the region.

I'll plan on doing that when I have a moment.

[ramink]

That sounds awesome, thanks! I just hope that in the case that the --region isn't used and AWS_REGION is not set, the error message is understandable enough that people, like me, who are using AssumeRole as some a HelloWorld for AWS will not be too discouraged.

In fact, even with the fix I mentioned above, I have not been able to get AssumeRole to work. I'm having a hard time figuring out what I'm doing wrong in my setup. A ReadMe that has easy-to-follow instructions on how to set up the Users, Roles, and authorisations needed for successful execution, would be very helpful. Something like:

If you have not already set up an AWS account with users, etc, you can follow these steps to set things up:

1. Create an AWS account following the instructions here (link).
2. Create a IAM user called AssumeRoleTest by ...
3. Make note of the ARN for the Role we assigned in test 2 by ...
4. Pass in the key, secret and ARN to AssumeRole by ....

[shepazon]

The example now accepts a --region argument that lets you specify a Region to use. Other examples likely need this update as well. I will do that as time permits.