listvalidator: Consider Validator to Ensure No Duplicate Elements

[bflad]

Terraform CLI and Framework Versions

Any, terraform-plugin-framework v0.13.0

Use Cases or Problem Statement

Certain providers may wish to implement a native "ordered set" type (e.g. a list with ordering requirements, but also element uniqueness constraints). Rather than implementing an awkward type abstraction in the framework or a separate type, we can introduce a list validator that will raise an error if duplicate list elements exist on any list type. (This doesn't preclude the introduction of a separate type with this validation baked in, however this validation is generic in nature.)

Proposal

Create a new listvalidator package validator called UniqueElements or similar that raises an error diagnostic if multiple elements have an equal attr.Value.

Additional Information

hashicorp/terraform-plugin-framework#99

Code of Conduct

• I agree to follow this project's Code of Conduct

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