Expose Files() runner method to Server

[jonathansp]

Abstract

This PR exposes Files() method to tflint-plugin-sdk. Current implementation already has the File(filename string) method exposed.

Rationale

Linting is the process of spotting potential errors. These errors can cause problems not only during the code execution but also to the business logic. Clean and organised files are often mandatory to maintainability. Some rules, however, make sense to one specific project or company. tflint-plugin-sdk helps to extend tflint in a way where each company can implement their own set of rules.

Use cases

This PR exposes the Files() method in order to allow the developer to create more low-level/business-specific rules. A few examples are:

• Checks if the body of a provider is empty, where the company does not allow it.
• Keeps blocks in alphabetical order, when needed, for cleansing aspects.
• Helps to stick to business-defined naming conventions.
• Helps to block cross-environment actions, dev to prod and vice-versa.

Arguably, some of these rules can be achieved in other ways, but once we can extend tflinf in plugins, I think its utilisation is correct in these cases. This PR depends on https://github.com/terraform-linters/tflint-plugin-sdk/pull/122/files already merged.

Closes:

• API missing method to walk through providers tflint-plugin-sdk#118
• how to retrieve or iterate all files tflint-plugin-sdk#119

Any improvement that you guys think to this PR, I will be happy to change.

[bendrucker]

Have a look at the failing checks. Also, a PR description indicating how you plan to use this would be helpful.

[jonathansp]

cc @wata727

[jonathansp]

Have a look at the failing checks. Also, a PR description indicating how you plan to use this would be helpful.

PR description updated.

[wata727]

👍

[jonathansp]

Thanks @wata727

Now we can write rules like:

func (rule *MyProjectOnlyAllowedFilesRule) Check(runner tflint.Runner) error {
	files, _ := runner.Files()
	allowedFiles := map[string]bool{"providers.tf": true, "main.tf": true}

	for name := range files {
		_, filename := path.Split(name)

		if _, exists := allowedFiles[filename]; !exists {
			message := fmt.Sprintf("File %s is not allowed here.", filename)

			return runner.EmitIssue(rule, message, hcl.Range{Start: hcl.InitialPos})
		}
	}
	return nil
}

will output:

Error: File backend.tf is not allowed here. (my_project_only_allowed_files_rule)

  on  line 1:
   (source code not available)