cache: fix stale-while-revalidate and stale-if-error

Closes #3853

Signed-off-by: flakey5 <73616808+flakey5@users.noreply.github.com>

Author: flakey5

lib/cache/memory-cache-store.js

@@ -90,6 +90,7 @@ class MemoryCacheStore {
           headers: entry.headers,
           body: entry.body,
           etag: entry.etag,
+          cacheControlDirectives: entry.cacheControlDirectives,
           cachedAt: entry.cachedAt,
           staleAt: entry.staleAt,
           deleteAt: entry.deleteAt

lib/handler/cache-handler.js

@@ -113,6 +113,7 @@ class CacheHandler {
         statusMessage,
         headers: strippedHeaders,
         vary: varyDirectives,
+        cacheControlDirectives,
         cachedAt: now,
         staleAt,
         deleteAt
@@ -170,7 +171,7 @@ class CacheHandler {
  *
  * @param {number} statusCode
  * @param {Record<string, string | string[]>} headers
- * @param {import('../util/cache.js').CacheControlDirectives} cacheControlDirectives
+ * @param {import('../../types/cache-interceptor.d.ts').default.CacheControlDirectives} cacheControlDirectives
  */
 function canCacheResponse (statusCode, headers, cacheControlDirectives) {
   if (statusCode !== 200 && statusCode !== 307) {
@@ -217,7 +218,7 @@ function canCacheResponse (statusCode, headers, cacheControlDirectives) {
 /**
  * @param {number} now
  * @param {Record<string, string | string[]>} headers
- * @param {import('../util/cache.js').CacheControlDirectives} cacheControlDirectives
+ * @param {import('../../types/cache-interceptor.d.ts').default.CacheControlDirectives} cacheControlDirectives
  *
  * @returns {number | undefined} time that the value is stale at or undefined if it shouldn't be cached
  */
@@ -253,22 +254,36 @@ function determineStaleAt (now, headers, cacheControlDirectives) {
 
 /**
  * @param {number} now
- * @param {import('../util/cache.js').CacheControlDirectives} cacheControlDirectives
+ * @param {import('../../types/cache-interceptor.d.ts').default.CacheControlDirectives} cacheControlDirectives
  * @param {number} staleAt
  */
 function determineDeleteAt (now, cacheControlDirectives, staleAt) {
+  let staleWhileRevalidate = -Infinity
+  let staleIfError = -Infinity
+
   if (cacheControlDirectives['stale-while-revalidate']) {
-    return now + (cacheControlDirectives['stale-while-revalidate'] * 1000)
+    staleWhileRevalidate = now + (cacheControlDirectives['stale-while-revalidate'] * 1000)
+  }
+
+  if (cacheControlDirectives['stale-if-error']) {
+    staleIfError = now + (cacheControlDirectives['stale-if-error'] * 1000)
   }
 
-  return staleAt
+  return Math.max(staleAt, staleWhileRevalidate, staleIfError)
 }
 
 /**
  * Strips headers required to be removed in cached responses
+<<<<<<< HEAD
  * @param {Record<string, string | string[]>} headers
  * @param {import('../util/cache.js').CacheControlDirectives} cacheControlDirectives
  * @returns {Record<string, string | string []>}
+=======
+ * @param {Buffer[]} rawHeaders
+ * @param {string[]} parsedRawHeaders
+ * @param {import('../../types/cache-interceptor.d.ts').default.CacheControlDirectives} cacheControlDirectives
+ * @returns {Buffer[]}
+>>>>>>> 45c0793e (cache: fix stale-while-revalidate and stale-if-error)
  */
 function stripNecessaryHeaders (headers, cacheControlDirectives) {
   const headersToRemove = ['connection']

lib/handler/cache-revalidation-handler.js

@@ -17,10 +17,12 @@ const assert = require('node:assert')
  */
 class CacheRevalidationHandler {
   #successful = false
+
   /**
    * @type {((boolean, any) => void) | null}
    */
   #callback
+
   /**
    * @type {(import('../../types/dispatcher.d.ts').default.DispatchHandler)}
    */
@@ -29,19 +31,26 @@ class CacheRevalidationHandler {
   #context
 
   /**
-   * @param {(boolean, any) => void} callback Function to call if the cached value is valid
-   * @param {import('../../types/dispatcher.d.ts').default.DispatchHandler} handler
+   * @type {boolean}
+   */
+  #allowErrorStatusCodes
+
+  /**
+   * @param {(boolean) => void} callback Function to call if the cached value is valid
+   * @param {import('../../types/dispatcher.d.ts').default.DispatchHandlers} handler
+   * @param {boolean} allowErrorStatusCodes
    */
-  constructor (callback, handler) {
+  constructor (callback, handler, allowErrorStatusCodes) {
     if (typeof callback !== 'function') {
       throw new TypeError('callback must be a function')
     }
 
     this.#callback = callback
     this.#handler = handler
+    this.#allowErrorStatusCodes = allowErrorStatusCodes
   }
 
-  onRequestStart (controller, context) {
+  onRequestStart (_, context) {
     this.#successful = false
     this.#context = context
   }
@@ -59,7 +68,9 @@ class CacheRevalidationHandler {
     assert(this.#callback != null)
 
     // https://www.rfc-editor.org/rfc/rfc9111.html#name-handling-a-validation-respo
-    this.#successful = statusCode === 304
+    // https://datatracker.ietf.org/doc/html/rfc5861#section-4
+    this.#successful = statusCode === 304 ||
+      (this.#allowErrorStatusCodes && statusCode >= 500 && statusCode <= 504)
     this.#callback(this.#successful, this.#context)
     this.#callback = null