InstancePrincipalsSecurityTokenSigner doesn't work without explicit federation endpoint

[nirvdrum]

The documentation and code samples both say that the federation_endpoint argument to the InstancePrincipalsSecurityTokenSigner constructor is optional. However, there's a logic error in the constructor's implementation that requires the federation endpoint to be supplied, otherwise it will default to a value of nil and will result in an ArgumentError in creating a URI from the federation client:

irb(main):001:0> instance_principals_signer = OCI::Auth::Signers::InstancePrincipalsSecurityTokenSigner.new
ArgumentError: bad argument (expected URI object or URI string)
	from /opt/graalvm/jre/languages/ruby/lib/mri/uri/common.rb:739:in `URI'
	from /opt/graalvm/jre/languages/ruby/lib/ruby/gems/2.4.0/gems/oci-2.3.5/lib/oci/auth/federation_client.rb:40:in `initialize'
	from /opt/graalvm/jre/languages/ruby/lib/ruby/gems/2.4.0/gems/oci-2.3.5/lib/oci/auth/signers/instance_principals_security_token_signer.rb:77:in `new'
	from /opt/graalvm/jre/languages/ruby/lib/ruby/gems/2.4.0/gems/oci-2.3.5/lib/oci/auth/signers/instance_principals_security_token_signer.rb:77:in `initialize'
	from (irb):2:in `new'
	from (irb):2
	from /opt/graalvm/jre/languages/ruby/bin/irb:29:in `<main>'

The issue is in the following block used to conditionally assign the federation endpoint value:

@federation_endpoint = if defined?(federation_endpoint)
                          federation_endpoint
                       else
                          "#{OCI::Regions.get_service_endpoint(@region, :Auth)}/v1/x509"
                       end

Since federation_endpoint is a keyword argument with a default value, it is always defined. defined?(federation_endpoint) => local-variable. The simple fix is to change the predicate to if federetion_endpoint. It's not clear if the code was implemented in this way to support an end user explicitly passing a false-y value. However, if a user does explicitly do that, the code is still going to error out several layers removed from where the error occurs.

On a side note, the published docs for the federation_endpoint value is truncated because the yard doc comment wraps. I don't know off-hand if there's a way to wrap it and generate properly or if you'd just need to accept wider-than-you-want comments for fields like this.

[andy-miles]

Thanks for the investigation and pointing out the bug. I'll review and address the issues you cited.

[andy-miles]

Fixes for instance principals are included with the 2.5.1 release. It's also available via RubyGems.

Please update your oci gem and verify that it addresses your issues.