Tool to import CloudFormation yaml sections

cf-merge

#!/usr/bin/env node
const { existsSync, readFileSync } = require("fs");
const path = require('path');
const APP = "cf-merge";

// https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-anatomy.html
const TOP_LEVEL_TOKENS = [
  "AWSTemplateFormatVersion",
  "Description",
  "Metadata",
  "Parameters",
  "Mappings",
  "Conditions",
  "Transform",
  "Resources",
  "Outputs"
];

const SECTION_REGEX = new RegExp(`^(${TOP_LEVEL_TOKENS.join('|')}):`, 'gm');

function main(filePath) {
  if (String(filePath).trim().length === 0) {
    throw new TypeError(`[${APP}] Expected a file path as the first argument`);
  }

  filePath = path.resolve(filePath)

  if (!existsSync(filePath)) {
    throw new Error(`[${APP}] Could not find '${filePath}' on disk`);
  }

  let file = readFileSync(filePath, "utf8");
  const includeMatches = [...file.matchAll(/# @include (.+?)$/gm)];

  includeMatches.forEach(match => {
    // e.g. ['# @include ./main.yml#Resources', './main.yml#Resources']
    const [includeStatement, resource] = match;
    // e.g. ['./main.yml', 'Resources']
    const [relativeImportFilePath, section] = resource.split("#");
    const resolvedImportFilePath = path.normalize(path.join(path.dirname(filePath), relativeImportFilePath));
    const importedFile = readFileSync(resolvedImportFilePath, "utf8");
    const sections = importedFile.match(SECTION_REGEX);
    const nextSection = sections[sections.indexOf(`${section}:`) + 1] || null;
    const partial = importedFile.split(`${section}:`)[1].split(nextSection)[0];
    file = file.replace(includeStatement, `# imported from ${resolvedImportFilePath}\n${partial}`);
  });

  console.log(file);
}

main(...process.argv.slice(2));