Show 'providers' information

[khos2ow]

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Description

This PR adds new functionality to show providers information. This was originally added in #113 by @moatra which we decided to introduce it in its own PR for the sake of cleaner history.

Issues Resolved

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Checklist

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• I have read the Contributing Guidelines.

Tests

• I have added tests to cover my changes.
• All tests pass when I run make test.

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Code Style

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[metmajer]

@khos2ow should we display provider information optionally?

[khos2ow]

I think after a little while showing provider information will become mainstream, and instead of opt-in approach I had thought to add new flags for opt-out approach, --no-providers, --no-inputs, --no-outputs. What do you think?

[metmajer]

@khos2ow I like that approach! That will create a breaking change in how things are displayed, and we should be 1) transparent about this in the release documentation and 2) ping our power users.

[crisp2u]

Guys, how is this supposed to work ? I guess it will show the same output as Providers Requirements section from terraform-config-inspect ? Or terraform providers ? Can you provide some examples based on the test data ?

[khos2ow]

@crisp2u it looks for required_providers but it's not the only way to look for the providers, we're also looking for all the managed and data resources to discover the providers (module.go#134).

Also you can find the generated content here based on our example.

resource "tls_private_key" "baz" {}

data "aws_caller_identity" "current" {
  provider = "aws"
}
data "aws_caller_identity" "ident" {
  provider = "aws.ident"
}
terraform {
  required_providers {
    aws = ">= 2.15.0"
  }
}
resource "null_resource" "foo" {}

will generate

 ## Providers

| Name | Version |
|------|---------|
| aws | >= 2.15.0 |
| aws.ident | >= 2.15.0 |
| null | n/a |
| tls | n/a |

[crisp2u]

Thanks for the examples pointer. I'm getting some weird output from my code but i'll try to isolate it and come back with some info