set-version.js

let setVersion = function (fileContent, version, buildNumberOnly) {
  const versionStringRx = /\d+(\.\d+){2,}/ig;

  if (!buildNumberOnly && (!version || !version.match(versionStringRx))) {  
      throw new Error('Invalid version string');    
  }

  if (buildNumberOnly && (!version || !version.match(/^[0-9]+$/ig))) {
    throw new Error('Invalid version string');
  }

  const lines = fileContent.split('\n');
  const versionLine = lines.find(l => l.match(/^version\s*=\s*/ig));
  let currentVersion = versionLine.match(versionStringRx);
  currentVersion = currentVersion && currentVersion[0];
  const newVersion = !buildNumberOnly ? version : currentVersion.replace(/[0-9]+$/, version);

  return {
    version: newVersion,
    content: lines.map(l => {
      if (l !== versionLine) {
        return l;
      }
      return versionLine.replace(currentVersion, newVersion);
    }).join('\n')
  };
};

module.exports = setVersion;