Loopback v3.x boot script to automatically update schemas for any datasources that have models connected to them.

0-schema-update.js

'use strict';
const debug = require('debug')('custom:boot:schema-update');

/*  Name:     0-schema-update.js
 *  Purpose:  Automatically updates all data sources to match current model definitions
 *  Warnings: ds.autoupdate does a diff and updates table schemas so it's a non-destructive
 *            change, but if you remove a property/column then data will be lost!!!
 *  See more: https: //loopback.io/doc/en/lb3/Creating-a-database-schema-from-models.html#auto-update
 */

function checkSchema(ds, dsName, cb) {
  debug(`Checking the ${dsName} schema`);

  ds.isActual(function(err, actual) {
    if (err) return debug(err);

    if (actual) {
      // schema is current, we bail
      debug(`datasource ${dsName} is up to date`);
    } else {
      // schema needs to be updated
      ds.autoupdate(function(err) {
        if (err) return debug(err);

        debug(`datasource ${dsName} updated`);
      });
    }
  });
}

// synchronous boot script
module.exports = function(app) {
  // for some reason, loopback returns a Title case and lowercase name for the same datasource
  // so we're going to .filter that noise out so SQLs don't get executed twice
  const sources = Object.keys(app.dataSources);
  const datasources = sources.filter(function(item, index) {
    return sources.indexOf(item.toLowerCase()) >= index;
  });

  debug(datasources);
  datasources.forEach(dsName => {
    const ds = app.dataSources[dsName];

    // if we're not connected yet, we wait for the ds connected event to occur
    // to prevent bogus EventEmitter memory leak warnings in the console.
    // see more: https://github.com/strongloop/loopback/issues/1186
    if (ds.connected) {
      checkSchema(ds, dsName);
    } else {
      ds.once('connected', () => {
        checkSchema(ds, dsName);
      });
    }
  });
};