Improve UX for different versions of the same module

[dbanck]

Background

In #874, we introduced links from the module source to the documentation for registry modules. We use the module source and the module version to build the URL.

When someone uses different versions of the same module, the only latest module call will be stored and used to build the link.

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "3.14.0"
}

module "vpc_legacy" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "2.78.0"
}

This problem occurs because of the way we generate dependency keys for dependent schemas. The current approach only uses the source as an identifier and ignores the version.

Taking the version into account will provide better autocompletion and link to the correct version of the module when accessing the documentation.

Challenges

• A module version can contain version-constraints (e.g. >= 3.0.0, < 3.14.0) which first need to be resolved to a version before they can be matched
• A module version can be omitted, so the latest version is assumed
• If version becomes a dependency key in the schema it will lead to unintended effects, like another link inside the body

Proposal

hcl-lang

• Add a new field to AttributeSchema to mark an attribute as linkable

terraform-schema

• Extend SchemaForModule to take the module version into account when building schemas for dependent module blocks
• Mark the version attribute for module blocks as dependency key
• Mark the source attribute for module blocks as linkable

TODO?