fix(cache): prevent bloom filter from rejecting reads on existing caches (#20)

The bloom filter was incorrectly blocking all reads from existing caches
because it was empty on startup - it wasn't populated from the persisted
cache data.

Added _bloomPopulated flag that is only set to true when keys are added
via set(). The bloom filter check in fetch() and has() now only applies
when this flag is true, allowing reads from existing caches to work.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: indexzero

src/cache/cache.js

@@ -13,9 +13,10 @@ export class Cache {
     this.bloomSize = options.bloomSize || 10000;
     this.bloomFalsePositiveRate = options.bloomFalsePositiveRate || 0.01;
     this._bloomInitialized = false;
+    this._bloomPopulated = false; // True only when bloom filter is populated from existing data
     this._inflightRequests = new Map();
     this._driverInitialized = false;
-    
+
     if (!this.driver) {
       throw new Error('Storage driver is required');
     }
@@ -61,12 +62,13 @@ export class Cache {
   async _doFetch(key, options = {}) {
     const driver = await this._ensureDriver();
     await this._initBloomFilter();
-    
-    // Check bloom filter first for non-existence
-    if (this.bloomFilter && !this.bloomFilter.has(key)) {
+
+    // Only use bloom filter if it was pre-populated (e.g., loaded from disk)
+    // An empty bloom filter would incorrectly reject all keys from existing caches
+    if (this.bloomFilter && this._bloomPopulated && !this.bloomFilter.has(key)) {
       return null; // Definitely not in cache
     }
-    
+
     try {
       const value = await driver.get(key);
       // Handle cache validation, ETags, etc.
@@ -82,20 +84,21 @@ export class Cache {
   async set(key, value, options = {}) {
     const driver = await this._ensureDriver();
     await this._initBloomFilter();
-    
-    // Add to bloom filter
+
+    // Add to bloom filter and mark as populated
     if (this.bloomFilter) {
       this.bloomFilter.add(key);
+      this._bloomPopulated = true;
     }
     return driver.put(key, value, options);
   }
 
   async has(key) {
     const driver = await this._ensureDriver();
     await this._initBloomFilter();
-    
-    // Check bloom filter first
-    if (this.bloomFilter && !this.bloomFilter.has(key)) {
+
+    // Only use bloom filter if it was pre-populated
+    if (this.bloomFilter && this._bloomPopulated && !this.bloomFilter.has(key)) {
       return false; // Definitely not in cache
     }
     return driver.has(key);