avm-tf-codestyle

name	avm-tf-codestyle
description	Use for AVM Terraform file layout, HCL style, variables, outputs, validation, lifecycle syntax, provider requirements, and Avm.Authoring formatting.

AVM Terraform Code Style

Fetch the current Terraform non-functional specifications through https://azure.github.io/Azure-Verified-Modules/llms.txt. Current module examples can lag the specification and are not authoritative.

Standard file layout

TFNFR39 applies to the root module and every submodule:

File	Requirement	Contents
terraform.tf	MUST	The single terraform {} block with required Terraform and provider versions.
variables.tf	MUST	Variable blocks.
outputs.tf	MUST	Output blocks.
main.tf	MUST	Primary resource, data, and module blocks.
locals.tf	Required when locals exist	Local values only.

Large modules may use main.<topic>.tf, variables.<topic>.tf, outputs.<topic>.tf, and locals.<topic>.tf. Topic names are snake case and each file contains only the block kind indicated by its prefix.

Do not add root-level providers.tf, module.tf, or everything.tf. Reusable AVM modules declare provider requirements but never provider configurations.

Each module and submodule also includes _header.md and _footer.md; README.md is generated.

Provider requirements

TFNFR25 requires a minimum and maximum Terraform CLI constraint, while TFFR3 requires the AzAPI provider range. Use the governance-managed baseline; a compliant current shape is:

terraform {
  required_version = ">= 1.9, < 2.0"

  required_providers {
    azapi = {
      source  = "Azure/azapi"
      version = "~> 2.12"
    }
  }
}

Do not raise required_version only because non-empty ignore_body_changes needs Terraform 1.11. Emit null when that interface is unused so earlier supported Terraform versions remain compatible.

Naming and declarations

• Use snake case for Terraform identifiers.
• Name the primary AzAPI resource this; name satellite resources after their purpose.
• Give every variable and output a precise type and description.
• Mark secret variables and outputs sensitive and follow the current ephemeral-value requirements.
• Default collections to {} or [] with nullable = false.
• Use optional(...) for non-required object attributes and give defaults that match the documentation.
• Keep variable, local, resource, module, and output ordering consistent with the transforms applied by avm transform.
• Prefer discrete computed outputs over whole-resource outputs.

Example:

variable "private_endpoints" {
  type = map(object({
    name               = optional(string)
    subnet_resource_id = string
  }))
  default  = {}
  nullable = false

  validation {
    condition = alltrue([
      for endpoint in values(var.private_endpoints) :
      can(provider::azapi::parse_resource_id("Microsoft.Network/virtualNetworks/subnets", endpoint.subnet_resource_id))
    ])
    error_message = "Each private endpoint subnet must be a valid subnet resource ID."
  }

  description = "A map of private endpoints to create."
}

TFNFR38 requires provider::azapi::parse_resource_id with a literal expected resource type for ARM resource IDs. Short-circuit optional values and iterate collections or nested attributes. Do not use regex, startswith, length, or split as substitutes, except for the prescribed generic check on an extension-resource module's polymorphic parent_id under TFRMFR1.

AzAPI block requirements

Every AzAPI resource must:

• source type from the deterministic field in var.resource_types;
• declare response_export_values;
• declare replace_triggers_refs;
• assign retry = var.retry;
• emit timeouts through a dynamic block; and
• assign the per-resource ignore_body_changes list, collapsing empty to null.

See avm-tf-azapi for the complete pattern.

Lifecycle syntax

Terraform lifecycle references are expressions, not strings:

lifecycle {
  ignore_changes = [tags]
}

Use static lifecycle.ignore_changes for compile-time-static references. Use the consumer-configurable AzAPI ignore_body_changes interface when body paths are dynamic. Body paths are strings because they are passed to the provider:

ignore_body_changes = length(var.ignore_body_changes.example_widgets) > 0 ? var.ignore_body_changes.example_widgets : null

Generated and managed files

• Edit _header.md or _footer.md, not README.md.
• Do not hand-edit managed telemetry or provider-version content that avm sync or avm transform owns.
• Keep comments rare and limited to non-obvious constraints or documented exceptions.

Formatting and validation

Use the PowerShell module rather than individual binaries:

avm transform
avm format
avm docs
avm pre-commit

Review and commit all resulting changes, then run:

avm pr-check

avm pr-check requires a clean Git worktree. Do not use Make, the old repository launcher, a container, Porch, or a separately installed formatter to approximate these checks.