<!-- Hi there, Thank you for opening an issue. Please note that we try to keep the Terraform issue tracker reserved for bug reports and feature requests. For general usage questions, please see: https://www.terraform.io/community.html. If your issue relates to a specific Terraform provider, please open it in the provider's own repository. The index of providers is at https://github.com/terraform-providers . --> ### Terraform Version <!--- Run `terraform -v` to show the version, and paste the result between the ``` marks below. If you are not running the latest version of Terraform, please try upgrading because your issue may have already been fixed. --> This bug exists from v0.12.0 to v0.12.5. ### Expected Behavior `terraform output` should verify that its argument is a valid identifier and produce an error if not. ``` $ terraform output anything.not.valid Error: Invalid output name An output name must begin with a letter or underscore, and contain only letters, digits, underscores, and dashes. ``` ### Actual Behavior Terraform just tries to look up the given name in the map of outputs and finds nothing, giving the generic error: ``` $ terraform output anything.not.valid The output variable requested could not be found in the state file. If you recently added this to your configuration, be sure to run `terraform apply`, since the state won't be updated with new output variables until that command is run. ``` This is bothersome because it suggests a course of action that won't actually improve the situation. If the root module doesn't have any output values defined at all then the message is instead about that: ``` $ terraform output anything.not.valid The state file either has no outputs defined, or all the defined outputs are empty. Please define an output in your configuration with the `output` keyword and run `terraform refresh` for it to become available. If you are using interpolation, please verify the interpolated value is not empty. You can use the `terraform console` command to assist. ``` While this message is technically correct, it's more important to report that the argument isn't valid because a syntax error on the command line can be indicative of misunderstanding the interface of this command, like running `terraform output output.foo` instead of `terraform output foo`, or of trying to access child module outputs (which are not available) like `terraform output module.foo.output.bar`. ### Steps to Reproduce Run `terraform output invalid.name`. ### References This was originally raised in #22126.