feat: support provider aliases

[suzuki-shunsuke]

#331

Follow up #332 (comment)

[suzuki-shunsuke]

It failed to parse the attribute provider.

resource "aws_instance" "reverse_proxy_a01" {
  ami           = "ami-088da9557aae42f39"
  instance_type = "t3.micro"
  key_name      = "bootstrap"
  provider      = aws.us-east-1
}

func (r *Runner) AwsClient(attributes hclext.Attributes) (*Client, error) {
	provider := "aws"
	if attr, exists := attributes["provider"]; exists {
		if diags := gohcl.DecodeExpression(attr.Expr, nil, &provider); diags.HasErrors() {
			logger.Error("parse provider attribute")
			return nil, diags
		}
		logger.Info("provider: " + provider)
	}

	awsClient, ok := r.AwsClients[provider]
	if !ok {
		return nil, fmt.Errorf("aws provider %s isn't found", provider)
	}

	return awsClient, nil
}

23:10:22 [DEBUG] runtime/asm_arm64.s:1259: tflint-ruleset-aws: 23:10:22 [ERROR] aws/runner.go:50: parse provider attribute
23:10:22 [DEBUG] runtime/asm_arm64.s:1259: tflint-ruleset-aws: 23:10:22 [ERROR] interceptor/logging.go:18: failed to gRPC request: direction=host2plugin method=/proto.RuleSet/Check err="rpc error: code = Aborted desc = Failed to check `aws_instance_invalid_key_name` rule: main.tf:24,19-22: Variables not allowed; Variables may not be used here., and 1 other diagnostic(s)"
Failed to check ruleset; Failed to check `aws_instance_invalid_key_name` rule: main.tf:24,19-22: Variables not allowed; Variables may not be used here., and 1 other diagnostic(s)

---

		if diags := gohcl.DecodeExpression(attr.Expr, nil, &provider); diags.HasErrors() {

  provider      = aws.us-east-1

Variables not allowed; Variables may not be used here

https://www.terraform.io/language/providers/configuration#selecting-alternate-provider-configurations

$ terraform validate
Success! The configuration is valid.

[wata727]

Umm... As you say, it seems that it is necessary to reimplement the decodeProviderConfigRef.
https://github.com/hashicorp/terraform/blob/3fbedf25430ead97eb42575d344427db3c32d524/internal/configs/resource.go#L498

I think we doesn't need to reproduce all implementations completely, for example, support for legacy configuration language can be ignored. The important thing is to get the list of traversals with hcl.AbsTraversalForExpr and get the root name and step name.

[suzuki-shunsuke]

67a6433 Copied required code.
It seems to work well.
I guess we have to take the original code's license into account.

[suzuki-shunsuke]

Mozilla Public License, version 2.0
https://github.com/hashicorp/terraform/blob/main/LICENSE

[wata727]

I noticed that the client is not initialized as before if you don't declare any provider blocks. Previously, if you wrote a credential in .tflint.hcl, you should have been able to enable deep checking without a provider block. e.g.

plugin "aws" {
  enabled = true
  access_key = "AWS_ACCESS_KEY",
  secret_key = "AWS_SECRET_KEY",
}

resource "aws_instance" "foo" {
  ami = "invalid"
}

[suzuki-shunsuke]

Fixed. f73855a

[suzuki-shunsuke]

https://github.com/terraform-linters/tflint-ruleset-aws/blob/master/docs/deep_checking.md#shared-credentials
https://github.com/terraform-linters/tflint-ruleset-aws/blob/master/docs/deep_checking.md#static-credentials

If these configurations are defined in the provider block, they will also be taken into account. But the priority is lower than the above way.
The priority is higher than the environment variable and lower than the above way.

Hmm... Maybe we have to fix f73855a according to the priority.

[suzuki-shunsuke]

The priority of plugin setting is higher than provider.

[suzuki-shunsuke]

Fixed. 313f0da

[wata727]

You need to get the provider attribute explicitly like any other rule.

[suzuki-shunsuke]

Fixed. 821423f

[wata727]

Same as aws_instance_invalid_rule.

[suzuki-shunsuke]

Fixed. 821423f

[wata727]

I guess we have to take the original code's license into account.

Yes. We changed TFLint's license 4 years ago to follow this case. MPL 2.0 is a weak copyleft and the Large Work is allowed under the same license.
terraform-linters/tflint#245

[wata727]

🎉

[suzuki-shunsuke]

Thank you for your support!