✨ enable partial view updates by default for CDN users without a proxy

packages/browser-rum-core/src/domain/configuration/configuration.spec.ts

@@ -486,6 +486,53 @@ describe('validateAndBuildRumConfiguration', () => {
     })
   })
 
+  describe('betaEnableViewUpdates', () => {
+    // Unit tests are bundled as a CDN build (webpack.base.ts pins `setup: 'cdn'`), so the npm
+    // side of the default is only covered by e2e and by reading the code.
+
+    it('defaults to true on a CDN build without a proxy', () => {
+      expect(validateAndBuildRumConfiguration(DEFAULT_INIT_CONFIGURATION)!.betaEnableViewUpdates).toBeTrue()
+    })
+
+    it('defaults to false on a CDN build with a proxy', () => {
+      expect(
+        validateAndBuildRumConfiguration({ ...DEFAULT_INIT_CONFIGURATION, proxy: 'https://proxy.example.com' })!
+          .betaEnableViewUpdates
+      ).toBeFalse()
+    })
+
+    it('defaults to false on a CDN build with a proxy function', () => {
+      expect(
+        validateAndBuildRumConfiguration({ ...DEFAULT_INIT_CONFIGURATION, proxy: () => 'https://proxy.example.com' })!
+          .betaEnableViewUpdates
+      ).toBeFalse()
+    })
+
+    it('honors an explicit false on a CDN build without a proxy', () => {
+      expect(
+        validateAndBuildRumConfiguration({ ...DEFAULT_INIT_CONFIGURATION, betaEnableViewUpdates: false })!
+          .betaEnableViewUpdates
+      ).toBeFalse()
+    })
+
+    it('honors an explicit true on a CDN build with a proxy', () => {
+      expect(
+        validateAndBuildRumConfiguration({
+          ...DEFAULT_INIT_CONFIGURATION,
+          betaEnableViewUpdates: true,
+          proxy: 'https://proxy.example.com',
+        })!.betaEnableViewUpdates
+      ).toBeTrue()
+    })
+
+    it('does not validate the configuration if it is not a boolean', () => {
+      expect(
+        validateAndBuildRumConfiguration({ ...DEFAULT_INIT_CONFIGURATION, betaEnableViewUpdates: 'yes' as any })
+      ).toBeUndefined()
+      expect(displayErrorSpy).toHaveBeenCalledOnceWith('"betaEnableViewUpdates" must be a boolean')
+    })
+  })
+
   describe('trackResourceHeaders', () => {
     describe('disabled', () => {
       it('defaults to empty array', () => {
@@ -919,6 +966,26 @@ describe('validateAndBuildRumConfiguration', () => {
 })
 
 describe('serializeRumConfiguration', () => {
+  describe('beta_enable_view_updates', () => {
+    it('reports the effective default on a CDN build without a proxy', () => {
+      expect(serializeRumConfiguration(DEFAULT_INIT_CONFIGURATION).beta_enable_view_updates).toBeTrue()
+    })
+
+    it('reports the effective default on a CDN build with a proxy', () => {
+      expect(
+        serializeRumConfiguration({ ...DEFAULT_INIT_CONFIGURATION, proxy: 'https://proxy.example.com' })
+          .beta_enable_view_updates
+      ).toBeFalse()
+    })
+
+    it('reports an explicitly disabled option', () => {
+      expect(
+        serializeRumConfiguration({ ...DEFAULT_INIT_CONFIGURATION, betaEnableViewUpdates: false })
+          .beta_enable_view_updates
+      ).toBeFalse()
+    })
+  })
+
   it('should serialize the configuration', () => {
     const exhaustiveRumInitConfiguration: Required<RumInitConfiguration> = {
       ...EXHAUSTIVE_INIT_CONFIGURATION,

packages/browser-rum-core/src/domain/configuration/configuration.ts

@@ -20,6 +20,9 @@ import type { RumPlugin } from '../plugins'
 import type { PropagatorType, TracingOption } from '../tracing/tracer.types'
 import { getRemoteConfigurationId } from './remoteConfiguration'
 
+// replaced at build time
+declare const __BUILD_ENV__SDK_SETUP__: string
+
 export const DEFAULT_PROPAGATOR_TYPES: PropagatorType[] = ['tracecontext', 'datadog']
 
 /**
@@ -350,6 +353,9 @@ export interface RumInitConfiguration extends InitConfiguration {
    * Enable partial view updates, which reduces bandwidth by sending only changed
    * fields instead of full view events on intermediate updates.
    *
+   * Enabled by default when the SDK is loaded from the CDN and no `proxy` is configured.
+   * Disabled by default otherwise, because a proxy may not forward the `view_update` event type.
+   *
    * @category Beta
    */
   betaEnableViewUpdates?: boolean | undefined
@@ -413,7 +419,7 @@ export const RUM_SCHEMA = {
   trackResources: { type: 'boolean', default: true, strict: false },
   trackLongTasks: { type: 'boolean', default: true, strict: false },
   trackViewsManually: { type: 'boolean', default: false, strict: false },
-  betaEnableViewUpdates: { type: 'boolean', default: false },
+  betaEnableViewUpdates: { type: 'boolean' },
   betaTrackWebSockets: { type: 'boolean', default: false, strict: false },
   enablePrivacyForActionName: { type: 'boolean', default: true },
   propagateTraceBaggage: { type: 'boolean', default: true },
@@ -491,12 +497,25 @@ export const RUM_SCHEMA = {
 
 export type RumConfiguration = Omit<InferredConfig<typeof RUM_SCHEMA>, 'allowedTracingUrls'> & {
   allowedTracingUrls: TracingOption[]
+  betaEnableViewUpdates: boolean
   rulePsr: number | undefined
   trackResourceHeaders: MatchHeader[]
   allowedGraphQlUrls: GraphQlUrlOption[]
   remoteConfigurationId: string | undefined
 }
 
+/**
+ * Partial view updates are enabled by default for CDN users that do not go through a proxy: a
+ * proxy may not forward the `view_update` event type yet, and npm users pin an SDK version so
+ * they opt in explicitly. An explicit `betaEnableViewUpdates` always takes precedence.
+ *
+ * The CDN check is temporary, the next step is to default this to true unless `proxy` is set.
+ * TODO next major: remove the option.
+ */
+function isViewUpdatesEnabledByDefault(proxy: InitConfiguration['proxy']): boolean {
+  return __BUILD_ENV__SDK_SETUP__ === 'cdn' && !proxy
+}
+
 export function validateAndBuildRumConfiguration(
   initConfiguration: RumInitConfiguration
 ): RumConfiguration | undefined {
@@ -524,6 +543,7 @@ export function validateAndBuildRumConfiguration(
   return {
     ...config,
     sessionReplayCanvasRecording,
+    betaEnableViewUpdates: config.betaEnableViewUpdates ?? isViewUpdatesEnabledByDefault(config.proxy),
     allowedTracingUrls,
     beforeSend: config.beforeSend
       ? (catchUserErrors(config.beforeSend, 'beforeSend threw an error:') as typeof config.beforeSend)
@@ -718,7 +738,7 @@ export function serializeRumConfiguration(configuration: RumInitConfiguration) {
     profiling_sample_rate: configuration.profilingSampleRate,
     use_remote_configuration_proxy: !!configuration.remoteConfigurationProxy,
     track_resource_headers: getTrackResourceHeadersTelemetryValue(configuration.trackResourceHeaders),
-    beta_enable_view_updates: configuration.betaEnableViewUpdates,
+    beta_enable_view_updates: configuration.betaEnableViewUpdates ?? isViewUpdatesEnabledByDefault(configuration.proxy),
     beta_track_web_sockets: configuration.betaTrackWebSockets,
     ...baseSerializedConfiguration,
   } satisfies RawTelemetryConfiguration