delay init poc

.changeset/friendly-mails-heal.md

@@ -0,0 +1,5 @@
+---
+'@segment/analytics-next': patch
+---
+
+Add ability to delay initialization

packages/browser/src/browser/__tests__/analytics-pre-init.integration.test.ts

@@ -398,4 +398,16 @@ describe('Pre-initialization', () => {
       await ajsBrowser2
     })
   })
+
+  describe('Delayed initialization', () => {
+    it('Should be able to delay initialization ', async () => {
+      const analytics = new AnalyticsBrowser({ writeKey: 'foo' })
+      const track = analytics.track('foo')
+      await sleep(100)
+      expect(trackSpy).not.toBeCalled()
+      analytics.load()
+      await track
+      expect(trackSpy).toBeCalledWith('foo')
+    })
+  })
 })

packages/browser/src/browser/__tests__/typedef-tests/analytics-browser.ts

@@ -9,6 +9,12 @@ import { Group, User } from '../../../core/user'
  * They aren't meant to be run by anything but the typescript compiler.
  */
 export default {
+  'AnalyticsBrowser should accept settings': () => {
+    const analytics = new AnalyticsBrowser({ writeKey: 'foo' })
+    assertNotAny(analytics)
+    assertIs<AnalyticsBrowser>(analytics)
+    void analytics.track('foo')
+  },
   'AnalyticsBrowser should return the correct type': () => {
     const result = AnalyticsBrowser.load({ writeKey: 'abc' })
     assertNotAny(result)

packages/browser/src/browser/index.ts

@@ -75,6 +75,13 @@ export interface AnalyticsBrowserSettings extends AnalyticsSettings {
    * If provided, will override the default Segment CDN (https://cdn.segment.com) for this application.
    */
   cdnURL?: string
+
+  /**
+   * Wait for .load() call.
+   * Default is "false" for instantiation via AnalyticsBrowser.load (invokes .load immediately)
+   * and "true" for the AnalyticsBrowser constructor
+   */
+  lazy?: boolean
 }
 
 export function loadLegacySettings(
@@ -308,13 +315,38 @@ async function loadAnalytics(
   return [analytics, ctx]
 }
 
+const createDeferred = () => {
+  let resolve!: () => void
+  const promise = new Promise((_resolve) => {
+    resolve = () => _resolve(undefined)
+  })
+  return {
+    promise,
+    resolve,
+  }
+}
 /**
  * The public browser interface for this package.
  * Use AnalyticsBrowser.load to create an instance.
  */
 export class AnalyticsBrowser extends AnalyticsBuffered {
-  private constructor(loader: AnalyticsLoader) {
-    super(loader)
+  _resolve: Function
+  load(): void {
+    // if user wants to invoke .load immediately after instantiation want to resolve immediately
+    this._resolve()
+  }
+
+  constructor(...args: Parameters<typeof AnalyticsBrowser['load']>) {
+    const [settings, options] = args
+    const lazy = settings.lazy ?? true
+    const { promise, resolve } = createDeferred()
+    super((buffer) =>
+      promise.then(() => loadAnalytics(settings, options, buffer))
+    )
+    if (!lazy) {
+      resolve()
+    }
+    this._resolve = resolve
   }
 
   /**
@@ -331,9 +363,7 @@ export class AnalyticsBrowser extends AnalyticsBuffered {
     settings: AnalyticsBrowserSettings,
     options: InitOptions = {}
   ): AnalyticsBrowser {
-    return new this((preInitBuffer) =>
-      loadAnalytics(settings, options, preInitBuffer)
-    )
+    return new this({ ...settings, lazy: false }, options)
   }
 
   static standalone(