Wrapper for `graphql-codegen` that only invokes the build if input files have been modified

graphql-codegen-if-modified.js

// Only invoke `graphql-codegen` if input files have been modified

const childProcess = require('child_process');
const fs = require('fs');
const glob = require('glob');
const {safeLoad} = require('js-yaml')

function main() {
  let args = process.argv.slice(2);
  let configPath = args[args.indexOf('--config') + 1];
  let config = safeLoad(fs.readFileSync(configPath, 'utf-8'));

  if (!shouldGenerate(config)) {
    console.log('Skipping generation');
    return;
  }
  childProcess.spawn('yarn', ['graphql-codegen', ...args], {
    stdio: ['ignore', 'inherit', 'inherit'],
  });
}

function shouldGenerate(config) {
  let outputFiles = Object.keys(config.generates);
  try {
    var newestGenerated = Math.min(...outputFiles.map(filename => fs.statSync(filename).mtime));
  } catch (err) {
    console.error('Output file is missing', err);
    return true;
  }

  let inputFiles = glob.sync(config.schema);
  return inputFiles.some(inputFile => {
    if (fs.statSync(inputFile).mtime >= newestGenerated) {
      console.log('Schema file modified:', inputFile);
      return true;
    }
  });
}

main();