Module outputs aren't evaluated: for_each over module.<name>.<output> drops the block #116

When C3X parses HCL, an expression that reads a module output (module.<name>.<output>) never resolves. A resource's for_each/count built from one fails, and the block is dropped. An attribute set from one falls back to the catalog default. This happens even when the output is only a literal.

Repro (c3x 0.3.20, darwin/arm64)

mods/sizes/main.tf:

locals {
  sizes = { prod = { class = "db.m7g.large" } }
}
output "sizes"  { value = local.sizes }
output "queues" { value = ["a", "b"] }

mods/db/main.tf:

variable "class"  { type = string }
variable "queues" { type = list(string) }

resource "aws_db_instance" "x" {
  engine            = "postgres"
  instance_class    = var.class
  allocated_storage = 50
}

resource "aws_sqs_queue" "q" {
  for_each = toset(var.queues)
  name     = each.key
}

root/main.tf:

provider "aws" { region = "eu-west-1" }

module "sizes" { source = "../mods/sizes" }

module "db" {
  source = "../mods/db"
  class  = module.sizes.sizes["prod"].class
  queues = module.sizes.queues
}

resource "aws_db_instance" "direct" {
  engine            = "postgres"
  instance_class    = module.sizes.sizes["prod"].class
  allocated_storage = 50
}

c3x estimate --path root --format json gives:

• module.db.aws_sqs_queue.q is dropped: WARN for_each evaluation failed; block omitted ... Unsupported attribute: This object does not have an attribute named "queues".
• module.db.aws_db_instance.x and aws_db_instance.direct are both priced at the catalog default class, with unresolved_attribute: instance_class could not be evaluated from the configuration.

Terraform resolves all three: the queues are a and b, and the class is db.m7g.large.

Where it seems to come from

In internal/parser/terraform at v0.3.20, buildEvalContext (eval_context.go) sets var, local and data, plus extras (count/each) and resource references (resources.go). Nothing sets module. reservedRoot (resource_refs.go) reserves the name, and json_config.go skips output blocks. It looks like a module's outputs are never evaluated, and never exposed to the module that calls it.

Impact

Our roots get their sizing, queue and bucket lists from a shared, input-free module "cells". With C3X, one Environment's platform root comes to $41/month (Infracost: $535), and its workloads root comes to $0 (Infracost: $252). NAT gateways, ECS services, Lambda, CloudFront, SQS and the RDS class are all lost.