dynamically changes lifecycle ignore_changes

lifecycle_block.sh

#!/bin/bash

# DISCLAIMER: There is a lot of room for improvement in this script. It is a quick and dirty solution.

# Description: This script adds a lifecycle block to a resource or data source in a Terraform file focused on ignore_changes.
#  This can be useful in conjunction with terragrunt and its hooks:
#
#  terragrunt.hcl content:
#
#     terraform {
#       source = "git::https://github.com......"
#
#       before_hook "lifecycle_ignore_changes_random_password_this_length" {
#         commands     = ["apply", "plan"]
#         execute      = [
#           "lifecycle_block.sh",
#           "${get_repo_root()}/${path_relative_to_include()}",
#           "random_password",
#           "this",
#           "length, override_special",
#           # "\\ncreate_before_destroy = true\\n"
#         ]
#       }
#     }

# Variables
PATH_TO_TERRAGRUNT_CACHE="${1}/.terragrunt-cache"
NAME="$2"
IDENTIFIER="$3"
IGNORE_CHANGES="$4"
ADDITIONAL_LIFECYCLE_VALUES="$5"
IS_RESOURCE="${6:-true}"
[[ "$IS_RESOURCE" = "true" ]] && PREFIX="resource" || PREFIX="data"

# Tools
BIN_SED=$(which gsed || which sed)
BIN_AWK=$(which gawk || which awk)

# Function to print usage
print_usage() {
  echo "Usage: $0 <path-to-terragrunt-file> <name> <identifier> <ignore_changes> [additional_lifecycle_values] [is_resource]"
  echo "Example: $0 . random_password this \"length, min_lower, special\""
}

# Function to check arguments
check_arguments() {
  if [ -z "$NAME" ] || [ -z "$IDENTIFIER" ]; then
    print_usage
    exit 1
  fi
}

# Function to find file to modify
find_file() {
  local name=$1
  local identifier=$2
  local prefix=$3
  local file
  file=$(grep -Rl "${prefix} \"${name}\" \"${identifier}\"" . | grep -E \.tf$)
  echo "$file"
}

# Function to add lifecycle block
add_lifecycle_block() {
  local file_to_modify=$1
  "$BIN_SED" -i -e "/${PREFIX} \"${NAME}\" \"${IDENTIFIER}\"/a \ \ lifecycle \{\n\ \ \ \ ignore_changes = \[ $IGNORE_CHANGES \] \n $ADDITIONAL_LIFECYCLE_VALUES \}" $file_to_modify
}

# Main function
main() {
  # Check arguments
  check_arguments

  # Change directory
  OLD_DIR="$(pwd)"
  cd "$PATH_TO_TERRAGRUNT_CACHE"

  # Find file to modify
  file_to_modify=$(find_file "$NAME" "$IDENTIFIER" "$PREFIX")
  if [ -z "$file_to_modify" ]; then
    echo "Resource not found"
    exit 1
  fi

  echo "Patching lifecycle in $file_to_modify ..."

  # Check if lifecycle already exists
  if cat $file_to_modify | "$BIN_AWK" "/${PREFIX} \"${NAME}\" \"${IDENTIFIER}\"/,/^}$/" | grep -q "lifecycle {" > /dev/null; then
    echo "Lifecycle already exists. Ignoring this script."
    exit 0
  fi

  # Add lifecycle block
  add_lifecycle_block $file_to_modify

  # Return to original directory
  cd "$OLD_DIR"
}

# Call main function
main