Version constraint operators on modules aren't working for prereleases

[ofhouse]

Terraform Version

Terraform v1.2.3

Terraform Configuration Files

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0"
    }
  }
}

provider "aws" {
  region = "us-west-2"
}

provider "aws" {
  alias  = "global_region"
  region = "us-east-1"
}


module "tf_next" {
  source  = "milliHQ/next-js/aws"
  version = "~> 1.0.0-canary.2"

  providers = {
    aws.global_region = aws.global_region
  }
}

Expected Behavior

When running terraform init the latest prerelease version of the module (1.0.0-canary.4) should be installed.

Actual Behavior

Initialization failed with the following error message:

Initializing modules...
╷
│ Error: Unresolvable module version constraint
│ 
│ There is no available version of module "registry.terraform.io/milliHQ/next-js/aws"
│ (main.tf:22) which matches the given version constraint. The newest available version
│ is 0.13.2.

Steps to Reproduce

1. terraform init

Additional Context

We currently publish prerelease versions in the semver version format v1.0.0-canary.x for our module Terraform Next.js for AWS to the public Terraform registry.
While in the prerelease phase we want to give our users the possibility to try out the new version.

We want to update the examples with a version constraint that always installs the latest available prerelease (e.g. ~> 1.0.0-canary.2).
The only other working solution is to use exact version numbers (e.g. 1.0.0-canary.4) in the examples, but this would mean that we have to update the version number in all of our examples for each new prerelease.

References

• Similar issue with required_version: Terraform doesn't understand pre-release required_version constraint  #28148
• Version constraint documentation: https://www.terraform.io/language/expressions/version-constraints

[jbardin]

Hi @ofhouse,

Because pre-release tags do not necessarily follow the normal semver order semantics, and one usually does not desire any pre-releases to be included in a range of semantic versions, they must only be defined with an exact version constraint. You can find this documented under Version Constraint Behavior.

We use GitHub issues for tracking bugs and enhancements, rather than for questions. While we can sometimes help with certain simple problems here, it's better to use the community forum where there are more people ready to help.

Thanks!

[ofhouse]

@jbardin Thanks for taking the time for the detailed response.
Yes, read over the part that says:

A prerelease version can be selected only by an exact version constraint.

So everything works as it should be from the definition.
What I instead want is that Terraform fully adapts Semver versioning, which is already covered in #17994.
Thanks for clarifying and sorry for the false bug report here.

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