add service worker flag to build command

src/build/build.ts

@@ -16,23 +16,21 @@ import * as del from 'del';
 import * as path from 'path';
 import * as logging from 'plylog';
 import {dest} from 'vinyl-fs';
-
-
 import mergeStream = require('merge-stream');
-import {PolymerProject, addServiceWorker} from 'polymer-build';
+import {PolymerProject, addServiceWorker, SWConfig} from 'polymer-build';
 
 import {OptimizeOptions, getOptimizeStreams} from './optimize-streams';
-
 import {ProjectConfig} from 'polymer-project-config';
 import {PrefetchTransform} from './prefetch';
 import {waitFor, pipeStreams} from './streams';
-import {parsePreCacheConfig} from './sw-precache';
+import {loadServiceWorkerConfig} from './load-config';
 
 const logger = logging.getLogger('cli.build.build');
 
 const buildDirectory = 'build/';
 
 export interface BuildOptions extends OptimizeOptions {
+  addServiceWorker?: boolean;
   swPrecacheConfig?: string;
   insertPrefetchLinks?: boolean;
   bundle?: boolean;
@@ -43,8 +41,6 @@ export async function build(
   const optimizeOptions:
       OptimizeOptions = {css: options.css, js: options.js, html: options.html};
   const polymerProject = new PolymerProject(config);
-  const swPrecacheConfig = path.resolve(
-      config.root, options.swPrecacheConfig || 'sw-precache-config.js');
 
   logger.info(`Deleting build/ directory...`);
   await del([buildDirectory]);
@@ -84,29 +80,39 @@ export async function build(
     logger.info('Generating build/ directory...');
   });
 
+  // Finish the build stream by piping it into the final build directory.
   buildStream = buildStream.pipe(dest(buildDirectory));
 
-
-  // While the build is in progress, parse the sw precache config
-  const swConfig = await parsePreCacheConfig(swPrecacheConfig);
-  if (swConfig) {
-    logger.debug(`Service worker config found`, swConfig);
-  } else {
-    logger.debug(`No service worker configuration found at ${swPrecacheConfig
-                  }, continuing with defaults`);
+  // If a service worker was requested, parse the service worker config file
+  // while the build is in progress. Loading the config file during the build
+  // saves the user ~300ms vs. loading it afterwards.
+  const swPrecacheConfigPath = path.resolve(
+      config.root, options.swPrecacheConfig || 'sw-precache-config.js');
+  let swConfig: SWConfig|null = null;
+  if (options.addServiceWorker) {
+    swConfig = await loadServiceWorkerConfig(swPrecacheConfigPath);
   }
 
-  // Now that the build stream has been set up, wait for it to complete.
+  // There is nothing left to do, so wait for the build stream to complete.
   await waitFor(buildStream);
 
   // addServiceWorker() reads from the file system, so we need to wait for
   // the build stream to finish writing to disk before calling it.
-  await addServiceWorker({
-    buildRoot: buildDirectory,
-    project: polymerProject,
-    swPrecacheConfig: swConfig || undefined,
-    bundled: options.bundle,
-  });
+  if (options.addServiceWorker) {
+    logger.info(`Generating service worker...`);
+    if (swConfig) {
+      logger.debug(`Service worker config found`, swConfig);
+    } else {
+      logger.debug(`No service worker configuration found at ` +
+          `${swPrecacheConfigPath}, continuing with defaults`);
+    }
+    await addServiceWorker({
+      buildRoot: buildDirectory,
+      project: polymerProject,
+      swPrecacheConfig: swConfig || undefined,
+      bundled: options.bundle,
+    });
+  }
 
   logger.info('Build complete!');
 }

src/build/sw-precache.ts → src/build/load-config.ts

@@ -17,9 +17,9 @@ import * as fs from 'fs';
 import * as logging from 'plylog';
 import {SWConfig} from 'polymer-build';
 
-let logger = logging.getLogger('cli.build.sw-precache');
+let logger = logging.getLogger('cli.build.load-config');
 
-export function parsePreCacheConfig(configFile: string):
+export function loadServiceWorkerConfig(configFile: string):
     Promise<SWConfig|null> {
   return new Promise<SWConfig|null>((resolve, _reject) => {
     fs.stat(configFile, (statError) => {

src/commands/build.ts

@@ -59,11 +59,21 @@ export class BuildCommand implements Command {
           'a minimum set of bundles. Useful for reducing the number of ' +
           'requests needed to serve your application.'
     },
+    {
+      name: 'add-service-worker',
+      type: Boolean,
+      description: 'Generate a service worker for your application to ' +
+          'cache all files and assets on the client.'
+    },
     {
       name: 'sw-precache-config',
+      type: String,
       defaultValue: 'sw-precache-config.js',
-      description: 'Path to an sw-precache configuration to be ' +
-          'used for service worker generation.'
+      description: 'Path to a file that exports configuration options for ' +
+          'the generated service worker. These options match those supported ' +
+          'by the sw-precache library. See ' +
+          'https://github.com/GoogleChrome/sw-precache#options-parameter ' +
+          'for a list of all supported options.'
     },
     {
       name: 'insert-prefetch-links',
@@ -80,6 +90,7 @@ export class BuildCommand implements Command {
     const build = require('../build/build').build;
 
     let buildOptions: BuildOptions = {
+      addServiceWorker: options['add-service-worker'],
       swPrecacheConfig: options['sw-precache-config'],
       insertPrefetchLinks: options['insert-prefetch-links'],
       bundle: options['bundle'],

test/unit/build/precache_test.js → test/unit/build/load-config_test.js

@@ -13,15 +13,15 @@
 const assert = require('chai').assert;
 const path = require('path');
 
-const precache = require('../../../lib/build/sw-precache');
+const loadServiceWorkerConfig = require('../../../lib/build/load-config').loadServiceWorkerConfig;
 
-suite('sw-precache', () => {
-  suite('parsePreCacheConfig()', () => {
-    test('should parse a js file', (done) => {
-      const configFile = path.resolve(__dirname, 'precache', 'config.js');
-      precache.parsePreCacheConfig(configFile).then((config) => {
+suite('load-config', () => {
+  suite('loadServiceWorkerConfig()', () => {
+    test('should parse the given js file', (done) => {
+      const configFile = path.resolve(__dirname, '../', 'fixtures', 'service-worker-config.js');
+      loadServiceWorkerConfig(configFile).then((config) => {
         assert.ok(config);
-        assert.property(config, 'staticFileGlobs');
+        assert.deepEqual(config.staticFileGlobs, ['*']);
         done();
       })
     });

test/unit/build/precache/config.js → test/unit/fixtures/service-worker-config.js

@@ -1,3 +1,3 @@
 module.exports = {
   staticFileGlobs: ['*'],
-}
+}