refactor(js): extract key derivation into a KeyResolver (#9032)

Co-authored-by: Robert Soriano <sorianorobertc@gmail.com>

Author: jacekradko

.changeset/sdk-139-extract-key-resolver.md

@@ -0,0 +1,5 @@
+---
+'@clerk/clerk-js': patch
+---
+
+Refactor the internal token cache so entry keys are derived through a dedicated `KeyResolver` module. This is an internal change with no effect on caching behavior or the public API.

packages/clerk-js/src/core/__tests__/keyResolver.test.ts

@@ -0,0 +1,37 @@
+import { describe, expect, it } from 'vitest';
+
+import { createKeyResolver } from '../keyResolver';
+
+describe('createKeyResolver', () => {
+  it('serializes a key as prefix::tokenId::audience', () => {
+    const resolver = createKeyResolver();
+    expect(resolver.toKey({ tokenId: 'session_123', audience: 'aud' })).toBe('clerk::session_123::aud');
+  });
+
+  it('defaults to the clerk prefix and an empty audience segment', () => {
+    const resolver = createKeyResolver();
+    expect(resolver.toKey({ tokenId: 'session_123' })).toBe('clerk::session_123::');
+  });
+
+  it('coalesces empty-string and undefined audience to the same key', () => {
+    const resolver = createKeyResolver();
+    expect(resolver.toKey({ tokenId: 'session_123', audience: '' })).toBe(resolver.toKey({ tokenId: 'session_123' }));
+  });
+
+  it('produces distinct keys for different audiences of the same tokenId', () => {
+    const resolver = createKeyResolver();
+    expect(resolver.toKey({ tokenId: 'same', audience: 'a' })).not.toBe(
+      resolver.toKey({ tokenId: 'same', audience: 'b' }),
+    );
+  });
+
+  it('isolates an audience-scoped key from the no-audience key of the same id', () => {
+    const resolver = createKeyResolver();
+    expect(resolver.toKey({ tokenId: 'same', audience: 'a' })).not.toBe(resolver.toKey({ tokenId: 'same' }));
+  });
+
+  it('respects a custom prefix', () => {
+    const resolver = createKeyResolver('custom');
+    expect(resolver.toKey({ tokenId: 'session_123' })).toBe('custom::session_123::');
+  });
+});

packages/clerk-js/src/core/keyResolver.ts

@@ -0,0 +1,35 @@
+/**
+ * Derives the opaque string keys used to address entries in the token store,
+ * keeping key construction out of the storage layer.
+ */
+
+const KEY_PREFIX = 'clerk';
+const DELIMITER = '::';
+
+/**
+ * Identifies a cached token entry by tokenId and optional audience.
+ */
+export interface TokenCacheKeyJSON {
+  audience?: string;
+  tokenId: string;
+}
+
+export interface KeyResolver {
+  /**
+   * Serializes a key to its string form `prefix::tokenId::audience`.
+   * Empty-string and undefined audience collapse to the same key.
+   */
+  toKey(key: TokenCacheKeyJSON): string;
+}
+
+/**
+ * Creates a {@link KeyResolver} bound to a key prefix.
+ *
+ * `audience` is currently unused by production (no caller sets it) but kept as a
+ * key dimension so an audience-scoped token can coexist with the session token
+ * of the same id. If it is revived, the cross-tab broadcast and Web Locks lock
+ * name must derive from the same key so all three agree.
+ */
+export const createKeyResolver = (prefix: string = KEY_PREFIX): KeyResolver => ({
+  toKey: ({ tokenId, audience }) => [prefix, tokenId, audience || ''].join(DELIMITER),
+});

packages/clerk-js/src/core/tokenCache.ts

@@ -4,18 +4,11 @@ import { debugLogger } from '@/utils/debug';
 import { TokenId } from '@/utils/tokenId';
 
 import { POLLER_INTERVAL_IN_MS } from './auth/SessionCookiePoller';
+import { createKeyResolver, type TokenCacheKeyJSON } from './keyResolver';
 import { Token } from './resources/internal';
 import { pickFreshestJwt } from './tokenFreshness';
 import { createTokenStore } from './tokenStore';
 
-/**
- * Identifies a cached token entry by tokenId and optional audience.
- */
-interface TokenCacheKeyJSON {
-  audience?: string;
-  tokenId: string;
-}
-
 /**
  * Cache entry containing token metadata and resolver.
  * Extends TokenCacheKeyJSON with additional properties for expiration tracking and token retrieval.
@@ -105,9 +98,6 @@ export interface TokenCache {
   size(): number;
 }
 
-const KEY_PREFIX = 'clerk';
-const DELIMITER = '::';
-
 /**
  * Default seconds before token expiration to trigger background refresh.
  * This threshold accounts for timer jitter, SafeLock contention (~5s), network latency,
@@ -122,36 +112,6 @@ const BACKGROUND_REFRESH_THRESHOLD_IN_SECONDS = 15;
 const BROADCAST = { broadcast: true };
 const NO_BROADCAST = { broadcast: false };
 
-/**
- * Converts between cache key objects and string representations.
- * Format: `prefix::tokenId::audience`
- */
-export class TokenCacheKey {
-  /**
-   * Parses a cache key string into a TokenCacheKey instance.
-   */
-  static fromKey(key: string): TokenCacheKey {
-    const [prefix, tokenId, audience = ''] = key.split(DELIMITER);
-    return new TokenCacheKey(prefix, { audience, tokenId });
-  }
-
-  constructor(
-    public prefix: string,
-    public data: TokenCacheKeyJSON,
-  ) {
-    this.prefix = prefix;
-    this.data = data;
-  }
-
-  /**
-   * Converts the key to its string representation for Map storage.
-   */
-  toKey(): string {
-    const { tokenId, audience } = this.data;
-    return [this.prefix, tokenId, audience || ''].join(DELIMITER);
-  }
-}
-
 /**
  * Message format for BroadcastChannel token synchronization between tabs.
  */
@@ -173,8 +133,9 @@ const generateTabId = (): string => {
  * Automatically manages token expiration and cleanup via scheduled timeouts.
  * BroadcastChannel support is enabled whenever the environment provides it.
  */
-const MemoryTokenCache = (prefix = KEY_PREFIX): TokenCache => {
+const MemoryTokenCache = (prefix?: string): TokenCache => {
   const store = createTokenStore<TokenCacheValue>();
+  const keyResolver = createKeyResolver(prefix);
   const tabId = generateTabId();
 
   let broadcastChannel: BroadcastChannel | null = null;
@@ -213,8 +174,8 @@ const MemoryTokenCache = (prefix = KEY_PREFIX): TokenCache => {
   const get = (cacheKeyJSON: TokenCacheKeyJSON): TokenCacheGetResult | undefined => {
     ensureBroadcastChannel();
 
-    const cacheKey = new TokenCacheKey(prefix, cacheKeyJSON);
-    const value = store.get(cacheKey.toKey());
+    const key = keyResolver.toKey(cacheKeyJSON);
+    const value = store.get(key);
 
     if (!value) {
       return;
@@ -233,7 +194,7 @@ const MemoryTokenCache = (prefix = KEY_PREFIX): TokenCache => {
       if (value.refreshTimeoutId !== undefined) {
         clearTimeout(value.refreshTimeoutId);
       }
-      store.delete(cacheKey.toKey());
+      store.delete(key);
       return;
     }
 
@@ -344,13 +305,11 @@ const MemoryTokenCache = (prefix = KEY_PREFIX): TokenCache => {
    * @param options - Configuration for cache behavior; broadcast controls whether to notify other tabs
    */
   const setInternal = (entry: TokenCacheEntry, options: { broadcast: boolean } = BROADCAST) => {
-    const cacheKey = new TokenCacheKey(prefix, {
+    const key = keyResolver.toKey({
       audience: entry.audience,
       tokenId: entry.tokenId,
     });
 
-    const key = cacheKey.toKey();
-
     // Clear timers from any existing entry for this key to prevent orphaned
     // refresh timers from accumulating across set() calls (e.g., from
     // #hydrateCache during _updateClient AND #refreshTokenInBackground).