Permissions check erroneously fails on self-hosted runner using an EC2 instance profile

[sciurus]

I have a self-hosted runner on an EC2 instance that has the necessary IAM permissions granted via its instance profile.

On this instance, I am able to successfully interact with CodeBuild via the AWS CLI and Node.js SDK.

However, attempting to use this action fails with the message "No credentials. Try adding @aws-actions/configure-aws-credentials earlier in your job to set up AWS credentials."

I think the assertion below is not correct. In some cases, credentials are available, they just have not been initialized yet. https://github.com/aws-actions/aws-codebuild-run-build/blob/c5df6288ba5ccdca9c023844569ccbe7bc3a4faa/code-build.js#L228-L231

The following test script can be used to demonstrate this.

const aws = require("aws-sdk");

const codeBuild = new aws.CodeBuild({
    customUserAgent: "aws-actions/aws-codebuild-run-build",
});

console.log("The credentials object before using the API: " + codeBuild.config.credentials);

codeBuild.listProjects(function (err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else console.log("The credentials object after using the API: " + codeBuild.config.credentials);   // successful response
});

If I run it on my EC2 instance, the output is

$ node test.js 
The credentials object before using the API: null
The credentials object after using the API: [object Object]

So you can see that it was null at first, which is why your assertion failed, but that the API call actually succeeded.

I think the assertion should be reworked somehow to be more robust, or you could just remove it and catch and report permissions failures.