terraform-filebase64sha256-reference.tf

# variables
variable "layer_file" {}
variable "layer_name" {}
variable "layer_runtime" {}
variable "deployment_bucket" {}
variable "deployment_file" {}

# compute hash
data "external" "hash" {
  program = ["/bin/sh", "${path.module}/filebase64sha256.sh", var.layer_file]
}

# upload layer to S3
resource "null_resource" "file" {
  triggers = {
    hash = data.external.hash.result.binary
    from = var.layer_file
    to   = var.deployment_key
  }
  provisioner "local-exec" {
    command = "aws s3 cp ${var.layer_file} s3://${var.deployment_bucket}/${var.deployment_key}-${data.external.hash.result.binary}"
  }
}

# create/update the layer
resource "aws_lambda_layer_version" "layer" {
  layer_name          = var.layer_name
  compatible_runtimes = [var.layer_runtime]
  s3_bucket           = var.deployment_bucket
  s3_key              = var.deployment_key
  source_code_hash    = data.external.hash.result.filebase64sha256
  depends_on          = [null_resource.file]
}