Format Dynamic Blocks in Terraform

Formatting Dynamic Blocks

Dynamic blocks replace repeated nested blocks with a programmatic approach. They add a level of complexity that makes formatting particularly important for understanding the generated structure.

Security Group Example

resource "aws_security_group" "web" {
  name        = "web-sg"
  description = "Security group for web servers"
  vpc_id      = aws_vpc.main.id

  dynamic "ingress" {
    for_each = var.ingress_rules
    content {
      from_port   = ingress.value.from_port
      to_port     = ingress.value.to_port
      protocol    = ingress.value.protocol
      cidr_blocks = ingress.value.cidr_blocks
      description = ingress.value.description
    }
  }

  dynamic "egress" {
    for_each = var.egress_rules
    content {
      from_port   = egress.value.from_port
      to_port     = egress.value.to_port
      protocol    = egress.value.protocol
      cidr_blocks = egress.value.cidr_blocks
    }
  }

  tags = {
    Name = "web-sg"
  }
}

IAM Policy Example

resource "aws_iam_policy" "custom" {
  name = "custom-policy"

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect = "Allow"
        Action = [
          "s3:GetObject",
          "s3:PutObject",
          "s3:ListBucket",
        ]
        Resource = [
          aws_s3_bucket.main.arn,
          "${aws_s3_bucket.main.arn}/*",
        ]
      }
    ]
  })
}

Formatting Conventions

• Dynamic block structure: dynamic "name" { for_each = ... content { ... } } has three levels of indentation
• Content block alignment: Attributes inside content are aligned at the deepest nesting level
• Iterator references: ingress.value.from_port uses the dynamic block name as the iterator by default
• Separation: Dynamic blocks are separated from static attributes by blank lines