Move resources across modules

[suzuki-shunsuke]

Feature Overview

Support moving resources across modules.
e.g.

null_resource.foo => module.foo.null_resource.foo
module.foo.null_resource.foo => module.bar.null_resource.foo
module.foo.null_resource.foo => null_resource.foo

In this case, it's hard to fix resource addresses, though it's possible to change resource references.

Why is the feature needed?

Feedback from users:

https://sweetops.slack.com/archives/CB6GHNLG0/p1735314890198529?thread_ts=1734997150.187929&cid=CB6GHNLG0

Sometimes we want to move resources across modules (a.b => module.c.a.d).

Example Code

No response

Note

No response

[suzuki-shunsuke]

tfmv doesn't refer files such as plan files and state files.
tfmv gets a list of resources from Terraform Configuration files, so it can't get resources in modules.
So it's hard to move specific resources in modules to others.

e.g.

module.foo.null_resource.foo => null_resource.foo

Or maybe we can support getting resources from states.

https://github.com/fujiwara/tfstate-lookup

[davidjeddy]

This would be super helpful foe module development and when abstraction resources to module. Do want.

[suzuki-shunsuke]

I created this issue based on user feedback. https://sweetops.slack.com/archives/CB6GHNLG0/p1735314890198529?thread_ts=1734997150.187929&cid=CB6GHNLG0
But I haven't understood the scenario well, so before working on this issue, we need to clarify needs and specification.

tfmv supports the following things now.

1. Modify the resource names
2. Modify the resource references
3. Generate moved blocks

Case 1. null_resource.foo => module.foo.null_resource.foo

For instance, a resource is managed out of the module.
When you start managing the resource in the module, you need to migrate it from null_resource.foo to module.foo.null_resource.foo.
In that case, you need to do the following things:

1. Remove the resource block null_resource.foo if it exists
2. Generate a moved block null_resource.foo => module.foo.null_resource.foo

Then we may be able to support the something like the following command:

tfmv -r "null_resource.foo/module.foo.null_resource.foo"

This isn't so useful when we run this command manually from terminal.
If we write a shell script to migrate resources across multiple Terraform Root Modules (i.e. Terraform Monorepo), it may be useful.

Case 2. module.foo.null_resource.foo => module.bar.null_resource.foo

In this case, you need to do the following things:

1. Generate a moved block module.foo.null_resource.foo => module.bar.null_resource.foo

This is not so useful.

Case 3. module.foo.null_resource.foo => null_resource.foo

In this case, you need to do the following things:

1. Generate the resource block null_resource.foo if it doesn't exist <= It's impossible unless tfmv refers a plan file or state
2. Generate a moved block module.foo.null_resource.foo => null_resource.foo

This is not so useful.

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Hmm, seems like I haven't understood needs well. 😅