Build all Angular apps in batches asynchronously

build-apps.js

const fs = require('fs'),
  spawn = require('child_process').spawn,
  // Custom output path.
  outputPath = '/nba-angular',
  // Number of projects to build asynchronously.
  batch = 3;

let ngCli;

function buildProject(project) {
  return new Promise((resolve, reject) => {
    let child = spawn('ng', ['build', '--project', project, '--prod', '--extract-licenses', '--build-optimizer', `--output-path=${outputPath}/dist/` + project]);

    child.stdout.on('data', (data) => {
      console.log(data.toString());
    });

    child.stderr.on('data', (data) => {
      process.stdout.write(data.toString());
    });

    child.on('close', (code) => {
      if (code === 0) {
        resolve(code);
      } else {
        reject(code);
      }
    });
  })
}

function filterProjects(projects) {
  return Object.keys(projects).filter(project => project.indexOf('e2e') === -1);
}

function batchProjects(projects) {
  let currentBatch = 0,
    i,
    batches = {};

  for (i = 0; i < projects.length; i += 1) {
    if ((i) % batch === 0) {
      currentBatch += 1;
    }
    if (typeof (batches['batch' + currentBatch]) === 'undefined') {
      batches['batch' + currentBatch] = [];
    }

    batches['batch' + currentBatch].push(projects[i]);
  }
  return batches;
}

fs.readFile('angular.json', 'utf8', async (err, data) => {
  let batches = {},
    batchesArray = [],
    i;

  if (err) {
    throw err;
  }

  ngCli = JSON.parse(data);

  batches = batchProjects(filterProjects(ngCli.projects));
  batchesArray = Object.keys(batches);

  for (i = 0; i < batchesArray.length; i += 1) {
    let promises = [];

    batches[batchesArray[i]].forEach((project) => {
      promises.push(buildProject(project));
    });

    console.log('Building projects ' + batches[batchesArray[i]].join(','));

    await Promise.all(promises).then(statusCode => {
      console.log('Projects ' + batches[batchesArray[i]].join(',') + ' built successfully!');
      if (i + 1 === batchesArray.length) {
        process.exit(0);
      }
    }, (reject, total) => {
      console.log(reject);
      process.exit(1);
    });
  }
});

I've updated this to build in batches of 3 apps at a time, but that is configurable. I'm also using async/await to try to simplify things, and switched to child_process spawn to further optimize how much memory the script uses.

👍

This would work out just fine in the ideal case if there is no cross dependency of libraries. But if there is a cross dependency this would fail. For example, we have 3 libraries

lib1
lib2
lib3

If lib3 is used inside lib2, while building lib2, since lib3 is not built yet, the build would fail.

Did you happen to face this? Any solution for this use case?