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fix(replay): detect and report rrweb silent initialization failure (#3174)
* fix(replay): detect and report rrweb silent initialization failure rrweb's record() wraps its entire body in a try-catch that silently swallows errors via console.warn and returns undefined. The SDK was not checking this return value, so it would report recording as active while rrweb never actually initialized - resulting in zero recording data being captured or flushed. Check the return value of rrwebRecord() in _startRecorder() and bail out with a new RRWEB_ERROR status if it fails. This makes the failure visible in SDK debug properties instead of silently losing data. * chore(replay): add changeset for rrweb init failure detection * fix(replay): fix lint and add mangled property name * fix(replay): address review feedback - Check _rrwebError flag directly in start() instead of redundantly setting it again, since _startRecorder() already sets the flag - Add $sdk_debug_replay_rrweb_error to debug properties
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‎.changeset/detect-rrweb-init-failure.md‎

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---
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"posthog-js": patch
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---
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Detect and report when rrweb fails to initialize. rrweb's `record()` silently swallows startup errors and returns `undefined`, which previously left the SDK reporting an active recording status while capturing zero data. The SDK now checks the return value and reports a new `rrweb_error` status, making the failure visible in debug properties.

‎packages/browser/src/__tests__/extensions/replay/lazy-sessionrecording.test.ts‎

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@@ -3071,6 +3071,80 @@ describe('Lazy SessionRecording', () => {
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})
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})
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describe('when rrweb record() returns undefined', () => {
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it('does not report recording as started', () => {
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loadScriptMock.mockImplementation((_ph: any, _path: any, callback: any) => {
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assignableWindow.__PosthogExtensions__.rrweb = {
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record: jest.fn(() => undefined),
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version: 'fake',
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wasMaxDepthReached: jest.fn(() => false),
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resetMaxDepthState: jest.fn(),
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}
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assignableWindow.__PosthogExtensions__.rrweb.record.takeFullSnapshot = jest.fn()
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assignableWindow.__PosthogExtensions__.rrweb.record.addCustomEvent = jest.fn()
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assignableWindow.__PosthogExtensions__.initSessionRecording = () => {
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return new LazyLoadedSessionRecording(posthog)
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}
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callback()
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})
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sessionRecording.onRemoteConfig(
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makeFlagsResponse({
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sessionRecording: {
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endpoint: '/s/',
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},
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})
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)
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expect(sessionRecording.started).toEqual(false)
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expect(sessionRecording.status).toEqual('rrweb_error')
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})
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it('recovers when rrweb starts successfully on retry', () => {
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let recordCallCount = 0
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loadScriptMock.mockImplementation((_ph: any, _path: any, callback: any) => {
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assignableWindow.__PosthogExtensions__.rrweb = {
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record: jest.fn(({ emit }) => {
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recordCallCount++
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if (recordCallCount === 1) {
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return undefined
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}
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_emit = emit
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return () => {}
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}),
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version: 'fake',
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wasMaxDepthReached: jest.fn(() => false),
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resetMaxDepthState: jest.fn(),
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}
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assignableWindow.__PosthogExtensions__.rrweb.record.takeFullSnapshot = jest.fn(() => {
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_emit(createFullSnapshot())
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})
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assignableWindow.__PosthogExtensions__.rrweb.record.addCustomEvent = jest.fn()
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assignableWindow.__PosthogExtensions__.initSessionRecording = () => {
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return new LazyLoadedSessionRecording(posthog)
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}
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callback()
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})
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sessionRecording.onRemoteConfig(
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makeFlagsResponse({
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sessionRecording: {
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endpoint: '/s/',
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},
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})
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)
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expect(sessionRecording.started).toEqual(false)
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expect(sessionRecording.status).toEqual('rrweb_error')
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// simulate session rotation triggering a restart
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sessionRecording['_lazyLoadedSessionRecording']!.start()
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expect(sessionRecording.started).toEqual(true)
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expect(sessionRecording.status).not.toEqual('rrweb_error')
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})
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})
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describe('buffering minimum duration', () => {
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it('can report no duration when no data', () => {
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sessionRecording.onRemoteConfig(

‎packages/browser/src/__tests__/extensions/replay/sessionRecordingStatus.test.ts‎

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@@ -8,6 +8,7 @@ import {
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LinkedFlagMatching,
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PAUSED,
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RecordingTriggersStatus,
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RRWEB_ERROR,
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SAMPLED,
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SessionRecordingStatus,
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TRIGGER_ACTIVATED,
@@ -30,6 +31,7 @@ const defaultTriggersStatus: RecordingTriggersStatus = {
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receivedFlags: true,
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isRecordingEnabled: true,
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isSampled: undefined,
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rrwebError: false,
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urlTriggerMatching: {
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onRemoteConfig: () => {},
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_instance: fakePostHog,
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const testCases: TestConfig[] = [
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// Basic states
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{
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name: 'rrweb error',
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config: { rrwebError: true },
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anyMatchExpected: RRWEB_ERROR,
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allMatchExpected: RRWEB_ERROR,
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},
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{
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name: 'rrweb error overrides sampling true',
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config: { rrwebError: true, isSampled: true },
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anyMatchExpected: RRWEB_ERROR,
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allMatchExpected: RRWEB_ERROR,
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},
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{
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name: 'rrweb error overrides active trigger',
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config: {
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rrwebError: true,
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urlTriggerMatching: {
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...defaultTriggersStatus.urlTriggerMatching,
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_instance: fakePostHog,
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triggerStatus: () => TRIGGER_ACTIVATED,
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} as unknown as URLTriggerMatching,
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},
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anyMatchExpected: RRWEB_ERROR,
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allMatchExpected: RRWEB_ERROR,
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},
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{
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name: 'flags not received',
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config: { receivedFlags: false },

‎packages/browser/src/extensions/replay/external/lazy-loaded-session-recorder.ts‎

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@@ -333,6 +333,7 @@ export class LazyLoadedSessionRecording implements LazyLoadedSessionRecordingInt
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*/
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private _queuedRRWebEvents: QueuedRRWebEvent[] = []
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private _isIdle: boolean | 'unknown' = 'unknown'
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private _rrwebError = false
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private _maxDepthExceeded = false
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private _linkedFlagMatching: LinkedFlagMatching
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this._makeSamplingDecision(this.sessionId)
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this._startRecorder()
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if (this._rrwebError) {
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return
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}
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// calling addEventListener multiple times is safe and will not add duplicates
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addEventListener(window, 'beforeunload', this._onBeforeUnload)
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addEventListener(window, 'offline', this._onOffline)
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isRecordingEnabled: true,
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// things that do still vary
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isSampled: this._isSampled,
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rrwebError: this._rrwebError,
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urlTriggerMatching: this._urlTriggerMatching,
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eventTriggerMatching: this._eventTriggerMatching,
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linkedFlagMatching: this._linkedFlagMatching,
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$sdk_debug_replay_flushed_size: this._flushedSizeTracker?.currentTrackedSize,
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$sdk_debug_replay_full_snapshots: this._fullSnapshotTimestamps,
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$snapshot_max_depth_exceeded: this._maxDepthExceeded,
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$sdk_debug_replay_rrweb_error: this._rrwebError,
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}
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}
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...sessionRecordingOptions,
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})
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if (!this._stopRrweb) {
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this._rrwebError = true
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logger.error(
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'rrweb failed to start - Loss of recording data is possible. Check the browser console for rrweb errors.'
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)
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return
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}
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this._rrwebError = false
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// We reset the last activity timestamp, resetting the idle timer
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this._lastActivityTimestamp = Date.now()
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// stay unknown if we're not sure if we're idle or not

‎packages/browser/src/extensions/replay/external/triggerMatching.ts‎

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@@ -15,6 +15,7 @@ export const BUFFERING = 'buffering'
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export const PAUSED = 'paused'
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export const PENDING_CONFIG = 'pending_config'
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export const LAZY_LOADING = 'lazy_loading'
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export const RRWEB_ERROR = 'rrweb_error'
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const TRIGGER = 'trigger'
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export const TRIGGER_ACTIVATED = TRIGGER + '_activated'
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get receivedFlags(): boolean
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get isRecordingEnabled(): false | true | undefined
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get isSampled(): false | true | null
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get rrwebError(): boolean
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get urlTriggerMatching(): URLTriggerMatching
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get eventTriggerMatching(): EventTriggerMatching
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get linkedFlagMatching(): LinkedFlagMatching
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* the sample rate determined this session should be sent to the server.
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*/
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// eslint-disable-next-line @typescript-eslint/no-unused-vars
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const sessionRecordingStatuses = [DISABLED, SAMPLED, ACTIVE, BUFFERING, PAUSED, PENDING_CONFIG, LAZY_LOADING] as const
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const sessionRecordingStatuses = [
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DISABLED,
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SAMPLED,
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ACTIVE,
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BUFFERING,
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PAUSED,
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PENDING_CONFIG,
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LAZY_LOADING,
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RRWEB_ERROR,
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] as const
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export type SessionRecordingStatus = (typeof sessionRecordingStatuses)[number]
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// while we have both lazy and eager loaded replay we might get either type of config
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// we need a no-op matcher before we can lazy-load the other matches, since all matchers wait on remote config anyway
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export function nullMatchSessionRecordingStatus(triggersStatus: RecordingTriggersStatus): SessionRecordingStatus {
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if (triggersStatus.rrwebError) {
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return RRWEB_ERROR
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}
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if (!triggersStatus.isRecordingEnabled) {
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return DISABLED
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}
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}
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export function anyMatchSessionRecordingStatus(triggersStatus: RecordingTriggersStatus): SessionRecordingStatus {
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if (triggersStatus.rrwebError) {
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return RRWEB_ERROR
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}
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if (!triggersStatus.receivedFlags) {
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return BUFFERING
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}
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}
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export function allMatchSessionRecordingStatus(triggersStatus: RecordingTriggersStatus): SessionRecordingStatus {
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if (triggersStatus.rrwebError) {
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return RRWEB_ERROR
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}
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if (!triggersStatus.receivedFlags) {
450473
return BUFFERING
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}

‎packages/browser/src/extensions/replay/types/rrweb.ts‎

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// Replication of `record` from inside `@rrweb/record`
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export type rrwebRecord = {
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(options: recordOptions): () => void
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(options: recordOptions): (() => void) | undefined
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addCustomEvent: (tag: string, payload: any) => void
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takeFullSnapshot: () => void
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mirror: {

‎packages/browser/terser-mangled-names.json‎

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"_resumeRecording",
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"_resumeSavedTour",
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"_retryQueue",
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"_rrwebError",
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"_runBeforeSend",
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"_sampleRate",
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"_samplingSessionListener",

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