feat: add localStorage strategy to remote config

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

@@ -478,6 +478,46 @@ describe('remoteConfiguration', () => {
       })
     })
 
+    describe('localStorage strategy', () => {
+      const LOCAL_STORAGE_KEY = 'dd_test_version'
+
+      beforeEach(() => {
+        localStorage.setItem(LOCAL_STORAGE_KEY, 'my-version')
+        registerCleanupTask(() => localStorage.removeItem(LOCAL_STORAGE_KEY))
+      })
+
+      it('should resolve a configuration value from localStorage', () => {
+        expectAppliedRemoteConfigurationToBe(
+          { version: { rcSerializedType: 'dynamic', strategy: 'localStorage', key: LOCAL_STORAGE_KEY } },
+          { version: 'my-version' }
+        )
+        expect(metrics.get().localStorage).toEqual({ success: 1 })
+      })
+
+      it('should resolve a configuration value from localStorage with an extractor', () => {
+        localStorage.setItem(LOCAL_STORAGE_KEY, 'version-123')
+        expectAppliedRemoteConfigurationToBe(
+          {
+            version: {
+              rcSerializedType: 'dynamic',
+              strategy: 'localStorage',
+              key: LOCAL_STORAGE_KEY,
+              extractor: { rcSerializedType: 'regex', value: '\\d+' },
+            },
+          },
+          { version: '123' }
+        )
+      })
+
+      it('should resolve to undefined if the key is missing', () => {
+        expectAppliedRemoteConfigurationToBe(
+          { version: { rcSerializedType: 'dynamic', strategy: 'localStorage', key: 'non_existent_key' } },
+          { version: undefined }
+        )
+        expect(metrics.get().localStorage).toEqual({ missing: 1 })
+      })
+    })
+
     describe('with extractor', () => {
       beforeEach(() => {
         setCookie(COOKIE_NAME, 'my-version-123', ONE_MINUTE)

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

@@ -44,6 +44,7 @@ export interface RemoteConfigurationMetrics extends Context {
   cookie?: RemoteConfigurationMetricCounters
   dom?: RemoteConfigurationMetricCounters
   js?: RemoteConfigurationMetricCounters
+  localStorage?: RemoteConfigurationMetricCounters
 }
 
 interface RemoteConfigurationMetricCounters {
@@ -147,6 +148,9 @@ export function applyRemoteConfiguration(
       case 'js':
         resolvedValue = resolveJsValue(property)
         break
+      case 'localStorage':
+        resolvedValue = resolveLocalStorageValue(property)
+        break
       default:
         display.error(`Unsupported remote configuration: "strategy": "${strategy as string}"`)
         return
@@ -164,6 +168,18 @@ export function applyRemoteConfiguration(
     return value
   }
 
+  function resolveLocalStorageValue({ key }: { key: string }) {
+    let value: string | null
+    try {
+      value = localStorage.getItem(key)
+    } catch {
+      metrics.increment('localStorage', 'failure')
+      return
+    }
+    metrics.increment('localStorage', value !== null ? 'success' : 'missing')
+    return value ?? undefined
+  }
+
   function resolveDomValue({ selector, attribute }: { selector: string; attribute?: string }) {
     let element: Element | null
     try {

packages/rum-core/src/domain/configuration/remoteConfiguration.types.ts

@@ -26,6 +26,13 @@ export type DynamicOption =
       extractor?: SerializedRegex
       [k: string]: unknown
     }
+  | {
+      rcSerializedType: 'dynamic'
+      strategy: 'localStorage'
+      key: string
+      extractor?: SerializedRegex
+      [k: string]: unknown
+    }
 
 /**
  * RUM Browser & Mobile SDKs Remote Configuration properties
@@ -73,6 +80,13 @@ export interface RumSdkConfig {
           extractor?: SerializedRegex
           [k: string]: unknown
         }
+      | {
+          rcSerializedType: 'dynamic'
+          strategy: 'localStorage'
+          key: string
+          extractor?: SerializedRegex
+          [k: string]: unknown
+        }
     /**
      * The percentage of sessions tracked
      */