show_version.js

#!/usr/bin/env node
"use strict";

const gitSemverTags = require('git-semver-tags');
const fs = require('fs');
const shelljs = require('shelljs');
const pkgJson = JSON.parse(fs.readFileSync('package.json'));

const opts = ['current', 'previous', 'workingcopy', 'tag'];
const yargs = require('yargs')
    .group(opts, 'Show version number of:')
    .option('workingcopy', {
      alias: 'w',
      boolean: true,
      description: `The working copy's package.json`
    })
    .option('current', {
      alias: 'c',
      boolean: true,
      description: 'The latest tagged version'
    })
    .option('previous', {
      alias: 'p',
      boolean: true,
      description: 'The second latest tagged version'
    })
    .option('tag', {
      alias: 't',
      string: true,
      description: 'A specific tag'
    })
    .group(['dep'], 'Show version number of a dependency:')
    .option('dep', {
      alias: 'd',
      string: true,
      description: 'The name of the dependency',
    })
    .check(argv => {
      const optsDesc = opts.map(opt => `--${opt}`).join(', ');

      if (opts.every(opt => !argv[opt])) throw new Error(`Specify one of: ${optsDesc}`);
      if (opts.filter(opt => !!argv[opt]).length > 1) throw new Error(`Opts ${optsDesc} are mutually exclusive`);

      return true;
    });

function getPkgJson() {
  const mode = opts.find(opt => yargs.argv[ opt ] && opt);

  const getPkgJsonForTag = (tag) =>
      JSON.parse(shelljs.exec('git show ' + tag + ':package.json', { silent: true }).stdout);

  switch (mode) {
    case 'workingcopy':
      return Promise.resolve(pkgJson);
    case 'current':
    case 'previous':
      return findTag(mode).then(getPkgJsonForTag);
    case 'tag':
      return Promise.resolve(getPkgJsonForTag(yargs.argv.tag));
    default:
      throw new Error(`Unknown mode: ${mode}`);
  }
}

function getSourceString() {
  switch (mode) {
    case 'workingcopy': return 'workingcopy';
    case 'current': return 'current tag';
    case 'previous': return 'previous tag';
    case 'tag': return `tag ${yargs.argv.tag}`;
  }
}

getPkgJson().then(json => {
  let dep = yargs.argv.dep;

  if (dep) {
    const depVer = json.dependencies && json.dependencies[ dep ];
    const devDepVer = json.devDependencies && json.devDependencies[ dep ];

    if (!depVer && !devDepVer) {
      console.error(JSON.stringify(json));
      throw new Error(`package.json from ${getSourceString()} has no dependencies["${dep}"] or devDependencies["${dep}"] key.`);
    }

    console.log((depVer || devDepVer).replace(/[^0-9a-zA-Z._+-]/g, ''));
  } else {
    console.log(json.version.replace(/[^0-9a-zA-Z._+-]/g, ''));
  }

  process.exit(0);
});

// previous or current
function findTag(mode) {
  return new Promise((resolve, reject) => {
    gitSemverTags(function (err, tags) {
      if (err) return reject(err);

      let tag;
      if (mode === 'current') tag = tags[0];
      if (mode === 'previous') tag = tags[1];

      if (tag) resolve(tag);

      reject("No tag found");
    });
  })
}