Generator of Terraform module wrappers (see results: https://github.com/terraform-aws-modules/terraform-aws-s3-bucket/tree/master/wrappers)

generate-terraform-wrappers.sh

#!/usr/bin/env bash

set -e

readonly CONTENT_MAIN_TF='module "wrapper" {}'
readonly CONTENT_VARIABLES_TF='variable "items" {
  description = "Maps of items to create a wrapper from. Values are passed through to the module."
  type        = any
  default     = {}
}'
readonly CONTENT_OUTPUTS_TF='output "wrapper" {
  description = "Map of outputs of a wrapper."
  value       = module.wrapper
}'
readonly CONTENT_VERSIONS_TF='terraform {
  required_version = ">= 0.13"
}'
readonly CONTENT_README='# WRAPPER_TITLE

The configuration in this directory contains an implementation of a single module wrapper pattern, which allows managing several copies of a module in places where using the native Terraform 0.13+ `for_each` feature is not feasible (e.g., with Terragrunt).

You may want to use a single Terragrunt configuration file to manage multiple resources without duplicating `terragrunt.hcl` files for each copy of the same module.

This wrapper does not implement any extra functionality.

## Usage with Terragrunt

`terragrunt.hcl`:

```hcl
terraform {
  source = "git::git@github.com:MODULE_REPO_ORG/terraform-aws-MODULE_REPO_SHORTNAME.git?ref=master//WRAPPER_PATH"
}

inputs = {
  items = {
    my-item = {
      # omitted... can be any argument supported by the module
    }
    my-second-item = {
      # omitted... can be any argument supported by the module
    }
    # omitted...
  }
}
```

## Usage with Terraform:

```hcl
module "wrapper" {
  source = "MODULE_REPO_ORG/MODULE_REPO_SHORTNAME/aws//WRAPPER_PATH"

  items = {
    my-item = {
      # omitted... can be any argument supported by the module
    }
    my-second-item = {
      # omitted... can be any argument supported by the module
    }
    # omitted...
  }
}
```

## Example: Manage multiple S3 buckets in one Terragrunt layer

`eu-west-1/s3-buckets/terragrunt.hcl`:

```hcl
terraform {
  source = "git::git@github.com:terraform-aws-modules/terraform-aws-s3-bucket.git?ref=master//wrappers"
}

inputs = {
  items = {
    bucket1 = {
      bucket        = "my-random-bucket-1"
      force_destroy = true
    }
    bucket2 = {
      bucket        = "my-random-bucket-2"
      force_destroy = true
    }
  }
}
```'

check_dependencies() {
  if [[ ! $(command -v hcledit) ]]; then
    echo "ERROR: The binary 'hcledit' is required by this script but is not installed or in the system's PATH."
    echo "Check documentation: https://github.com/minamijoyo/hcledit"
    exit 1
  fi
}

create_tmp_file_tf() {
  # Can't append extension for mktemp, so renaming instead
  tmp_file=$(mktemp "${TMPDIR:-/tmp}/tfwrapper-XXXXXXXXXX")
  mv "$tmp_file" "$tmp_file.tf"
  tmp_file_tf="$tmp_file.tf"

  echo "$CONTENT_MAIN_TF" > "$tmp_file_tf"
}

main() {
  check_dependencies

  local root_dir=$(git rev-parse --show-toplevel 2>/dev/null || pwd)
  local module_dir="" # empty (default) or modules/iam-user
  local wrapper_dir="wrappers"
  local module_repo_org="terraform-aws-modules"
  local module_repo_name=$(basename "$root_dir")
  local module_repo_shortname="${module_repo_name//terraform-aws-/}"
  local overwrite="false"
  local verbose="false"

  local relative_source_path="../"  # From "wrappers" to root_dir
  local newline="--newline"

  while [[ $# -gt 0 ]]; do
    local key="$1"

    case "$key" in
      --root-dir)
        root_dir="$2"
        shift
        ;;
      --module-dir)
        module_dir="$2"
        shift
        ;;
      --wrapper-dir)
        wrapper_dir="$2"
        shift
        ;;
      --module-repo-org)
        module_repo_org="$2"
        shift
        ;;
      --module-repo-shortname)
        module_repo_shortname="$2"
        shift
        ;;
      --overwrite)
        overwrite="true"
        ;;
      --verbose)
        verbose="true"
        ;;
      *)
        echo "ERROR: Unrecognized argument: $key"
        echo "Usage: $0 [--root-dir <root-dir>] [--module-dir <module-dir>] [--wrapper-dir <wrapper-dir>] [--module-repo-shortname <module-repo-shortname>] [--overwrite] [--verbose]"
        echo "Example 1: $0 --root-dir /Users/Bob/Sites/terraform-aws-modules/terraform-aws-s3-bucket --module-dir modules/object"
        echo "Example 2: $0 --module-dir modules/object"
        echo "Example 3: $0 --overwrite --verbose"
        exit 1
        ;;
    esac

    shift
  done

  if [[ -z "$root_dir" ]]; then
    echo "--root-dir can't be empty. Remove it to use default value."
    exit 1
  fi

  if [[ -z "$wrapper_dir" ]]; then
    echo "--wrapper-dir can't be empty. Remove it to use default value."
    exit 1
  fi

  if [[ -z "$module_repo_org" ]]; then
    echo "--module-repo-org can't be empty. Remove it to use default value."
    exit 1
  fi

  if [[ -z "$module_repo_shortname" ]]; then
    echo "--module-repo-shortname can't be empty. It should be part of full repo name (eg, s3-bucket)."
    exit 1
  fi

  if [ ! -d "$root_dir" ]; then
    echo "Root directory $root_dir does not exist!"
    exit 1
  fi

  full_module_dir="${root_dir}/${module_dir}"

  if [ ! -d "$full_module_dir" ]; then
    echo "Module directory $full_module_dir does not exist!"
    exit 1
  fi

  # Remove "modules/" from "modules/iam-user"
  module_name="${module_dir//modules\//}"
  if [ "$module_name" == "" ]; then
    wrapper_title="Wrapper for the root module"
    wrapper_path="${wrapper_dir}"
  else
    wrapper_title="Wrapper for module: \`${module_dir}\`"
    wrapper_path="${wrapper_dir}/${module_name}"
  fi

  # Wrappers will be stored in "wrappers/{module_name}"
  output_dir="${root_dir}/${wrapper_dir}/${module_name}"

  [ ! -d "$output_dir" ] && mkdir -p "$output_dir"

  # Calculate relative depth for module source by number of slashes
  module_depth="${module_dir//[^\/]}"
  for _ in $(seq "${#module_depth}"); do
    relative_source_path+="../"
  done

  create_tmp_file_tf

  if [ "$verbose" == "true" ]; then
    echo "Root directory: $root_dir"
    echo "Module directory: $module_dir"
    echo "Output directory: $output_dir"
    echo "Temp file: $tmp_file_tf"
    echo
  fi

  # Get names of module variables in all terraform files
  declare -a module_vars=($(cat "${full_module_dir}"/*.tf | hcledit block list | grep variable. | cut -d'.' -f 2))

  hcledit attribute append module.wrapper.source "\"${relative_source_path}${module_dir}\"" --newline -f "$tmp_file_tf" -u
  hcledit attribute append module.wrapper.for_each var.items --newline -f "$tmp_file_tf" -u

  for module_var in "${module_vars[@]}"; do
    # Get default value for the variable
    var_default=$(cat "${full_module_dir}"/*.tf | hcledit attribute get "variable.${module_var}.default")

    # Empty default means that the variable is required
    if [ "$var_default" == "" ]; then
      var_value="each.value.${module_var}"
    else
      var_value="lookup(each.value, \"${module_var}\", "$var_default")"
    fi

    hcledit attribute append "module.wrapper.${module_var}" "${var_value}" $newline -f "$tmp_file_tf" -u

    newline=""
  done

  if [ "$verbose" == "true" ]; then
    cat "$tmp_file_tf"
  fi

  if [ "$overwrite" == "true" ]; then
    echo "Saving files into ${output_dir}"

    mv "$tmp_file_tf" "${output_dir}/main.tf"
    echo "$CONTENT_VARIABLES_TF" > "${output_dir}/variables.tf"
    echo "$CONTENT_OUTPUTS_TF" > "${output_dir}/outputs.tf"
    echo "$CONTENT_VERSIONS_TF" > "${output_dir}/versions.tf"

    echo "$CONTENT_README" > "${output_dir}/README.md"
    sed -i "s#WRAPPER_TITLE#${wrapper_title}#g" "${output_dir}/README.md"
    sed -i "s#WRAPPER_PATH#${wrapper_path}#g" "${output_dir}/README.md"
    sed -i "s#MODULE_REPO_ORG#${module_repo_org}#g" "${output_dir}/README.md"
    sed -i "s#MODULE_REPO_SHORTNAME#${module_repo_shortname}#g" "${output_dir}/README.md"
  else
    echo "There is nothing to save. Add --overwrite flag to write files."
  fi

}

main "$@"