fix(misconf): properly expand dynamic blocks

[nikpivkin]

Description

This PR separates the logic for expanding dynamic blocks from expanding the for-each meta argument.

Related issues

• Close fix(terraform): handle for-each arguments properly #7611
• Close fix(terraform): expand dynamic blocks from top to bottom #7586

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[nikpivkin]

For reviewers: this test should not have run successfully because dynamic blocks do not create an each object.

[simar7]

In my coverage this seems to be untested so I decided to investigate. Would this ever be reached since we already check for !forEachVal.CanIterateElements() prior to this? If you have a sample input, it'd be nice to understand.

[nikpivkin]

Yes, this check is unreachable, I removed it. 4d3de2a

[wplj]

It looks like the issue is still there (0.57.0):

2024-11-04T11:26:35+01:00       ERROR   [terraform evaluator] Failed to expand block. Invalid "for-each" argument. Must be known and iterable.  block="module.app_vm.azurerm_backup_protected_vm.this" value="cty.NilVal"

I'm using the same module as before (https://github.com/Azure/terraform-azurerm-avm-res-compute-virtualmachine/blob/main/main.backup.tf)

[stewartcampbell]

I'm seeing similar issues still with 0.57.0:

2024-11-12T11:44:53Z    ERROR   [terraform evaluator] Failed to expand block. Invalid "for-each" argument. Must be known and iterable.  block="data.aws_subnet.ecs_cluster_vpc_private" value="cty.NilVal"
2024-11-12T11:44:53Z    ERROR   [terraform evaluator] Failed to expand dynamic block.   block="module.ecs_service.aws_ecs_service.aurora" err="2 errors occurred:\n\t* invalid for-each in aws_ecs_service.aurora.dynamic.ordered_placement_strategy block: cannot use a cty.NilVal value in for_each. An iterable collection is required\n\t* invalid for-each in aws_ecs_service.aurora.dynamic.ordered_placement_strategy block: cannot use a cty.NilVal value in for_each. An iterable collection is required\n\n"

[nikpivkin]

Hi @stewartcampbell !

You are using blocks of data that cannot be analyzed statically in some cases #7731 (comment)