1 files changed, 31 insertions, 6 deletions
diff --git a/ext/fetch/23_request.js b/ext/fetch/23_request.js
index b61f46c61..3058db6f7 100644
--- a/ext/fetch/23_request.js
+++ b/ext/fetch/23_request.js
@@ -43,6 +43,8 @@
 
   const _request = Symbol("request");
   const _headers = Symbol("headers");
+  const _getHeaders = Symbol("get headers");
+  const _headersCache = Symbol("headers cache");
   const _signal = Symbol("signal");
   const _mimeType = Symbol("mime type");
   const _body = Symbol("body");
@@ -52,7 +54,7 @@
    * @property {string} method
    * @property {() => string} url
    * @property {() => string} currentUrl
-   * @property {[string, string][]} headerList
+   * @property {() => [string, string][]} headerList
    * @property {null | typeof __window.bootstrap.fetchBody.InnerBody} body
    * @property {"follow" | "error" | "manual"} redirectMode
    * @property {number} redirectCount
@@ -64,7 +66,7 @@
   /**
    * @param {string} method
    * @param {string} url
-   * @param {[string, string][]} headerList
+   * @param {() => [string, string][]} headerList
    * @param {typeof __window.bootstrap.fetchBody.InnerBody} body
    * @param {boolean} maybeBlob
    * @returns
@@ -76,7 +78,16 @@
     }
     return {
       method,
-      headerList,
+      headerListInner: null,
+      get headerList() {
+        if (this.headerListInner === null) {
+          this.headerListInner = headerList();
+        }
+        return this.headerListInner;
+      },
+      set headerList(value) {
+        this.headerListInner = value;
+      },
       body,
       redirectMode: "follow",
       redirectCount: 0,
@@ -167,7 +178,21 @@
     /** @type {InnerRequest} */
     [_request];
     /** @type {Headers} */
-    [_headers];
+    [_headersCache];
+    [_getHeaders];
+
+    /** @type {Headers} */
+    get [_headers]() {
+      if (this[_headersCache] === undefined) {
+        this[_headersCache] = this[_getHeaders]();
+      }
+      return this[_headersCache];
+    }
+
+    set [_headers](value) {
+      this[_headersCache] = value;
+    }
+
     /** @type {AbortSignal} */
     [_signal];
     get [_mimeType]() {
@@ -210,7 +235,7 @@
       // 5.
       if (typeof input === "string") {
         const parsedURL = new URL(input, baseURL);
-        request = newInnerRequest("GET", parsedURL.href, [], null, true);
+        request = newInnerRequest("GET", parsedURL.href, () => [], null, true);
       } else { // 6.
         if (!ObjectPrototypeIsPrototypeOf(RequestPrototype, input)) {
           throw new TypeError("Unreachable");
@@ -451,7 +476,7 @@
     const request = webidl.createBranded(Request);
     request[_request] = inner;
     request[_signal] = signal;
-    request[_headers] = headersFromHeaderList(inner.headerList, guard);
+    request[_getHeaders] = () => headersFromHeaderList(inner.headerList, guard);
     return request;
   }