From bee9dd505f5700a95560087edee4f6a7e1221829 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Zugmeyer?= <benoit.zugmeyer@datadoghq.com>
Date: Wed, 13 Jan 2021 10:57:16 +0100
Subject: [PATCH] =?UTF-8?q?=E2=9A=97=E2=9C=A8=20[RUMF-819]=20postpone=20re?=
 =?UTF-8?q?cording?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../src/boot/rumRecorderPublicApi.spec.ts     | 50 ++++++++++++++++++-
 .../src/boot/rumRecorderPublicApi.ts          | 21 +++++++-
 2 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/packages/rum-recorder/src/boot/rumRecorderPublicApi.spec.ts b/packages/rum-recorder/src/boot/rumRecorderPublicApi.spec.ts
index 3a5c3b552c..360c2985c4 100644
--- a/packages/rum-recorder/src/boot/rumRecorderPublicApi.spec.ts
+++ b/packages/rum-recorder/src/boot/rumRecorderPublicApi.spec.ts
@@ -1,17 +1,25 @@
+import { Configuration } from '@datadog/browser-core'
 import { RumPublicApi, StartRum } from '@datadog/browser-rum-core'
 import { makeRumRecorderPublicApi, StartRecording } from './rumRecorderPublicApi'
 
 const DEFAULT_INIT_CONFIGURATION = { applicationId: 'xxx', clientToken: 'xxx' }
 
 describe('makeRumRecorderPublicApi', () => {
-  let rumGlobal: RumPublicApi
+  let rumGlobal: RumPublicApi & { startSessionRecord?(): void }
   let startRecordingSpy: jasmine.Spy<StartRecording>
   let startRumSpy: jasmine.Spy<StartRum>
+  let enabledFlags: string[] = []
 
   beforeEach(() => {
+    enabledFlags = []
     startRecordingSpy = jasmine.createSpy()
     startRumSpy = jasmine.createSpy().and.callFake(() => {
-      return ({} as unknown) as ReturnType<StartRum>
+      const configuration: Partial<Configuration> = {
+        isEnabled(flag: string) {
+          return enabledFlags.includes(flag)
+        },
+      }
+      return ({ configuration } as unknown) as ReturnType<StartRum>
     })
     rumGlobal = makeRumRecorderPublicApi(startRumSpy, startRecordingSpy)
   })
@@ -38,4 +46,42 @@ describe('makeRumRecorderPublicApi', () => {
       expect(getCommonContext().hasReplay).toBe(true)
     })
   })
+
+  describe('experimental flag postpone_start_recording', () => {
+    it('if disabled, startSessionRecord should not be defined', () => {
+      expect(rumGlobal.startSessionRecord).toBeUndefined()
+      rumGlobal.init(DEFAULT_INIT_CONFIGURATION)
+      expect(rumGlobal.startSessionRecord).toBeUndefined()
+    })
+
+    it('if enabled, recording should not start when calling init()', () => {
+      enabledFlags = ['postpone_start_recording']
+      rumGlobal.init(DEFAULT_INIT_CONFIGURATION)
+      expect(startRecordingSpy).not.toHaveBeenCalled()
+    })
+
+    it('if enabled, startSessionRecord should be defined', () => {
+      enabledFlags = ['postpone_start_recording']
+      expect(rumGlobal.startSessionRecord).toBeUndefined()
+      rumGlobal.init(DEFAULT_INIT_CONFIGURATION)
+      expect(rumGlobal.startSessionRecord).toEqual(jasmine.any(Function))
+    })
+
+    it('if enabled, commonContext.hasReplay should be true only if startSessionRecord is called', () => {
+      enabledFlags = ['postpone_start_recording']
+      rumGlobal.init(DEFAULT_INIT_CONFIGURATION)
+      expect(getCommonContext().hasReplay).toBe(false)
+      rumGlobal.startSessionRecord!()
+      expect(getCommonContext().hasReplay).toBe(true)
+    })
+
+    it('if enabled, calling startSessionRecord multiple times should only start recording once', () => {
+      enabledFlags = ['postpone_start_recording']
+      rumGlobal.init(DEFAULT_INIT_CONFIGURATION)
+      rumGlobal.startSessionRecord!()
+      rumGlobal.startSessionRecord!()
+      rumGlobal.startSessionRecord!()
+      expect(startRecordingSpy).toHaveBeenCalledTimes(1)
+    })
+  })
 })
diff --git a/packages/rum-recorder/src/boot/rumRecorderPublicApi.ts b/packages/rum-recorder/src/boot/rumRecorderPublicApi.ts
index 75d3c48527..79163fda19 100644
--- a/packages/rum-recorder/src/boot/rumRecorderPublicApi.ts
+++ b/packages/rum-recorder/src/boot/rumRecorderPublicApi.ts
@@ -1,3 +1,4 @@
+import { monitor } from '@datadog/browser-core'
 import { makeRumPublicApi, StartRum } from '@datadog/browser-rum-core'
 
 import { startRecording } from './recorder'
@@ -6,13 +7,29 @@ export type StartRecording = typeof startRecording
 
 export function makeRumRecorderPublicApi(startRumImpl: StartRum, startRecordingImpl: StartRecording) {
   const rumRecorderGlobal = makeRumPublicApi((userConfiguration, getCommonContext) => {
+    let isRecording = false
+
     const startRumResult = startRumImpl(userConfiguration, () => ({
       ...getCommonContext(),
-      hasReplay: true,
+      hasReplay: isRecording,
     }))
 
     const { lifeCycle, parentContexts, configuration, session } = startRumResult
-    startRecordingImpl(lifeCycle, userConfiguration.applicationId, configuration, session, parentContexts)
+
+    if (configuration.isEnabled('postpone_start_recording')) {
+      ;(rumRecorderGlobal as any).startSessionRecord = monitor(startSessionRecord)
+    } else {
+      startSessionRecord()
+    }
+
+    function startSessionRecord() {
+      if (isRecording) {
+        return
+      }
+
+      isRecording = true
+      startRecordingImpl(lifeCycle, userConfiguration.applicationId, configuration, session, parentContexts)
+    }
 
     return startRumResult
   })