pantheon-ai/terraform-validator

Comprehensive toolkit for validating, linting, testing, and automating Terraform configurations and HCL files. Use this skill when working with Terraform files (.tf, .tfvars), validating infrastructure-as-code, debugging Terraform configurations, performing dry-run testing with terraform plan, or working with custom providers and modules.

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Terraform Advanced Features

Name: pantheon-ai/terraform-validator
Author: pantheon-ai

Modern Terraform features for enhanced infrastructure management. This reference covers features introduced in Terraform 1.10+.

Official Documentation: developer.hashicorp.com/terraform

Ephemeral Values and Write-Only Arguments (1.10+)

Purpose: Securely manage sensitive data like passwords and tokens without storing them in Terraform state or plan files.

Overview

Ephemeral values are temporary values that exist only during a Terraform operation. They are never persisted to state, plan files, or logs. This is a major security improvement for secrets management.

Ephemeral Resources

Ephemeral resources generate temporary values that don't persist:

# Generate a temporary password - NOT stored in state
ephemeral "random_password" "db_password" {
  length           = 16
  override_special = "!#$%&*()-_=+[]{}<>:?"
}

# Use with AWS Secrets Manager
resource "aws_secretsmanager_secret" "db_password" {
  name = "db_password"
}

resource "aws_secretsmanager_secret_version" "db_password" {
  secret_id                = aws_secretsmanager_secret.db_password.id
  secret_string_wo         = ephemeral.random_password.db_password.result
  secret_string_wo_version = 1
}

Write-Only Arguments (1.11+)

Write-only arguments accept values but never persist them:

# Use ephemeral password with write-only argument
ephemeral "random_password" "db_password" {
  length = 16
}

resource "aws_db_instance" "example" {
  instance_class       = "db.t3.micro"
  allocated_storage    = "5"
  engine               = "postgres"
  username             = "admin"
  skip_final_snapshot  = true

  # Write-only argument - password is NOT stored in state
  password_wo          = ephemeral.random_password.db_password.result
  password_wo_version  = 1  # Increment to trigger password update
}

Key Concepts

Concept	Version	Description
`ephemeral` block	1.10+	Defines resources that are never stored in state
Ephemeral variables	1.10+	Variables marked `ephemeral = true`
Ephemeral outputs	1.10+	Outputs marked `ephemeral = true`
Write-only arguments	1.11+	Resource arguments ending in `_wo` that accept ephemeral values
`_wo_version` arguments	1.11+	Version tracking to prevent updates on every run
`ephemeralasnull` function	1.10+	Convert ephemeral to null for conditional logic

Ephemeral Input Variables

variable "api_token" {
  type      = string
  sensitive = true
  ephemeral = true  # Value is not stored in state
}

Ephemeral Outputs

output "generated_password" {
  value     = ephemeral.random_password.main.result
  ephemeral = true  # Value is not stored in state
}

Provider Support

Ephemeral resources are available in:

AWS Provider (secrets, passwords)
Azure Provider
Kubernetes Provider
Random Provider (random_password)
Google Cloud Provider

Security Best Practices

Always use ephemeral for secrets - passwords, API keys, tokens
Use write-only arguments - for database passwords, secret values
Increment version - when you need to update write-only values
Combine with Secrets Manager - store ephemeral values in vault
Never log ephemeral values - they won't appear in plan output

Validation Considerations

When validating Terraform configurations with ephemeral values:

Ephemeral resources don't appear in state
Write-only arguments show as (sensitive value) in plans
terraform plan will show ephemeral resource creation each run
Checkov may not detect issues in ephemeral resources (no state)

Actions Blocks (1.14+)

Purpose: Execute provider-defined imperative operations outside the normal CRUD model.

Overview

Actions are a concept in Terraform 1.14 (GA - November 2025) that allow providers to define operations that don't fit the standard create/read/update/delete lifecycle. This is useful for one-time operations like invoking Lambda functions or invalidating CDN caches.

Basic Example

# Define an action to invoke a Lambda function
action "aws_lambda_invoke" "process_data" {
  config {
    function_name = aws_lambda_function.processor.function_name
    payload       = jsonencode({ action = "process" })
  }
}

# CloudFront cache invalidation action
action "aws_cloudfront_create_invalidation" "invalidate_cache" {
  config {
    distribution_id = aws_cloudfront_distribution.cdn.id
    paths           = ["/*"]
  }
}

Advanced Example with Dependencies

# Resource with action trigger on lifecycle events
resource "aws_s3_object" "data_file" {
  bucket       = aws_s3_bucket.data.id
  key          = "data/input.json"
  source       = "local/input.json"
  content_type = "application/json"

  # Trigger action when S3 object is updated
  lifecycle {
    action_trigger {
      events  = [after_update]
      actions = [action.aws_lambda_invoke.process_data]
    }
  }
}

# Lambda invocation action - triggered by resource lifecycle
action "aws_lambda_invoke" "process_data" {
  config {
    function_name = aws_lambda_function.processor.function_name
    payload = jsonencode({
      bucket = aws_s3_bucket.data.id
      key    = aws_s3_object.data_file.key
      action = "process"
    })
  }
}

# CloudFront cache invalidation - triggered after S3 update
resource "aws_s3_object" "index_html" {
  bucket       = aws_s3_bucket.website.id
  key          = "index.html"
  content_type = "text/html"
  source       = "html/index.html"

  lifecycle {
    action_trigger {
      events  = [after_update]
      actions = [action.aws_cloudfront_create_invalidation.invalidate_cache]
    }
  }
}

action "aws_cloudfront_create_invalidation" "invalidate_cache" {
  config {
    distribution_id = aws_cloudfront_distribution.cdn.id
    paths           = ["/*"]
  }
}

Key Features

Imperative Operations - Actions perform side effects, not resource management
Lifecycle Integration - Can trigger on resource create/update/destroy
CLI Invocation - Run with terraform apply -invoke to trigger actions directly
Provider-Defined - Actions are defined by providers (AWS, Azure, etc.)
Chainable - Actions can depend on other actions

CLI Commands

# Plan with specific action invocation
terraform plan -invoke=action.aws_lambda_invoke.process_data

# Apply with specific action invocation
terraform apply -invoke=action.aws_lambda_invoke.process_data

# Apply with auto-approve and action invocation
terraform apply -auto-approve -invoke=action.aws_cloudfront_create_invalidation.invalidate_cache

# Normal apply (actions triggered by lifecycle events still run)
terraform apply

When to Use Actions

Invoking Lambda/Cloud Functions
Cache invalidation (CloudFront, CDN)
Stopping/starting EC2 instances
Database migrations
API calls that don't create resources
Post-deployment scripts
Integration testing triggers

Provider Support (as of November 2025)

Provider	Available Actions
AWS	`aws_lambda_invoke`, `aws_cloudfront_create_invalidation`, `aws_ec2_stop_instance`
Azure	Coming soon
GCP	Coming soon

Validation Considerations

Actions don't create resources in state
terraform plan shows action effects separately
Actions run in dependency order
Failed actions don't roll back completed actions

List Resources and Query Command (1.14+)

Purpose: Query and filter existing infrastructure resources directly from Terraform, with optional configuration generation for importing.

Overview

Terraform 1.14 introduces List Resources, defined in *.tfquery.hcl files, that allow you to query existing infrastructure and optionally generate Terraform configuration for discovered resources.

Basic Query File

# my_query.tfquery.hcl

# List all S3 buckets with specific tags
list "aws_s3_bucket" "production_buckets" {
  filter {
    tags = {
      Environment = "production"
    }
  }
}

# List EC2 instances by type
list "aws_instance" "large_instances" {
  filter {
    instance_type = "t3.large"
  }
}

# List all VPCs
list "aws_vpc" "all_vpcs" {}

CLI Commands

# Execute query and display results
terraform query

# Execute query with specific query file
terraform query -query=my_query.tfquery.hcl

# Generate configuration for discovered resources
terraform query -generate-config-out=discovered.tf

# Validate query files offline
terraform validate -query

Advanced Query Example

# infrastructure_audit.tfquery.hcl

# Find untagged resources
list "aws_s3_bucket" "untagged_buckets" {
  filter {
    tags = null
  }
}

# Find publicly accessible resources
list "aws_security_group" "public_ingress" {
  filter {
    ingress {
      cidr_blocks = ["0.0.0.0/0"]
    }
  }
}

# Find resources by name pattern
list "aws_instance" "web_servers" {
  filter {
    tags = {
      Name = "web-*"
    }
  }
}

Use Cases

Infrastructure Auditing - Discover resources not managed by Terraform
Compliance Checking - Find resources missing required tags
Cost Optimization - Identify oversized or unused resources
Import Generation - Generate configuration for manual imports
Drift Detection - Compare query results with state

Output Example

$ terraform query

List: aws_s3_bucket.production_buckets
  Found 3 resources:

  - arn:aws:s3:::prod-logs-bucket
    tags.Environment = "production"
    tags.Team = "ops"

  - arn:aws:s3:::prod-assets-bucket
    tags.Environment = "production"
    tags.Team = "web"

  - arn:aws:s3:::prod-backups-bucket
    tags.Environment = "production"
    tags.Team = "dba"

Validation Considerations

Query files are validated with terraform validate -query
Queries require valid provider authentication
Results depend on IAM permissions
Large queries may be rate-limited by cloud providers

Feature Version Matrix

Feature	Terraform Version	Status
Ephemeral resources	1.10+	GA
Ephemeral variables/outputs	1.10+	GA
Write-only arguments	1.11+	GA
S3 native state locking	1.11+	GA
Actions blocks	1.14+	GA (Nov 2025)
List resources / Query	1.14+	GA (Nov 2025)

pantheon-ai/terraform-validator

advanced_features.mdreferences/

Terraform Advanced Features

Ephemeral Values and Write-Only Arguments (1.10+)

Overview

Ephemeral Resources

Write-Only Arguments (1.11+)

Key Concepts

Ephemeral Input Variables

Ephemeral Outputs

Provider Support

Security Best Practices

Validation Considerations

Actions Blocks (1.14+)

Overview

Basic Example

Advanced Example with Dependencies

Key Features

CLI Commands

When to Use Actions

Provider Support (as of November 2025)

Validation Considerations

List Resources and Query Command (1.14+)

Overview

Basic Query File

CLI Commands

Advanced Query Example

Use Cases

Output Example

Validation Considerations

Feature Version Matrix

Related Documentation

pantheon-ai/terraform-validator

advanced_features.md.css-3qkkll{font-size:var(--chakra-font-sizes-sm);font-weight:var(--chakra-font-weights-normal);color:var(--chakra-colors-gray-300);}references/

Terraform Advanced Features

Ephemeral Values and Write-Only Arguments (1.10+)

Overview

Ephemeral Resources

Write-Only Arguments (1.11+)

Key Concepts

Ephemeral Input Variables

Ephemeral Outputs

Provider Support

Security Best Practices

Validation Considerations

Actions Blocks (1.14+)

Overview

Basic Example

Advanced Example with Dependencies

Key Features

CLI Commands

When to Use Actions

Provider Support (as of November 2025)

Validation Considerations

List Resources and Query Command (1.14+)

Overview

Basic Query File

CLI Commands

Advanced Query Example

Use Cases

Output Example

Validation Considerations

Feature Version Matrix

Related Documentation

advanced_features.mdreferences/