chore: Raise TypeScript baseline to 5.9 and adopt generic Uint8Array types.

package.json

@@ -51,8 +51,8 @@
     "prettier": "^3.3.3",
     "remark-parse": "^11.0.0",
     "remark-stringify": "^11.0.0",
-    "tsd": "^0.31.1",
-    "typescript": "^5.5",
+    "tsd": "^0.33.0",
+    "typescript": "^5.9.0",
     "unified": "^11.0.5"
   },
   "dependencies": {
@@ -64,5 +64,13 @@
     "esbuild": "^0.25.0",
     "magic-string": "^0.30.12",
     "regexpu-core": "^6.1.1"
+  },
+  "peerDependencies": {
+    "typescript": "^5.9.0"
+  },
+  "peerDependenciesMeta": {
+    "typescript": {
+      "optional": true
+    }
   }
 }

test-d/experimental.test-d.ts

@@ -8,7 +8,7 @@ import {
 } from 'fastly:experimental';
 import { expectType } from 'tsd';
 
-expectType<(path: string) => Uint8Array>(includeBytes);
+expectType<(path: string) => Uint8Array<ArrayBuffer>>(includeBytes);
 expectType<(enabled: boolean) => void>(enableDebugLogging);
 expectType<(base: URL | null | undefined) => void>(setBaseURL);
 expectType<(backend: string) => void>(setDefaultBackend);

test-d/globals.test-d.ts

@@ -390,7 +390,8 @@ import { expectError, expectType } from 'tsd';
   expectType<URLSearchParams>(
     new URLSearchParams({
       [Symbol.iterator]: function* () {
-        yield '';
+        yield ['', ''];
+        return;
       },
     }),
   );
@@ -458,7 +459,7 @@ import { expectError, expectType } from 'tsd';
   expectError(new TextEncoder(''));
   const encoder = new TextEncoder();
   expectType<TextEncoder>(encoder);
-  expectType<(input?: string) => Uint8Array>(encoder.encode);
+  expectType<(input?: string) => Uint8Array<ArrayBuffer>>(encoder.encode);
   expectType<'utf-8'>(encoder.encoding);
   expectError((encoder.encoding = 'd'));
 }
@@ -484,7 +485,7 @@ import { expectError, expectType } from 'tsd';
   expectType<(address: string) => Geolocation>(
     fastly.getGeolocationForIpAddress,
   );
-  expectType<(path: string) => Uint8Array>(fastly.includeBytes);
+  expectType<(path: string) => Uint8Array<ArrayBuffer>>(fastly.includeBytes);
 }
 
 // CompressionStream
@@ -494,9 +495,9 @@ import { expectError, expectType } from 'tsd';
   let stream = new CompressionStream('deflate');
   stream = new CompressionStream('deflate-raw');
   stream = new CompressionStream('gzip');
-  expectType<ReadableStream<Uint8Array>>(stream.readable);
+  expectType<ReadableStream<Uint8Array<ArrayBuffer>>>(stream.readable);
   expectError((stream.readable = 'd'));
-  expectType<WritableStream<Uint8Array>>(stream.writable);
+  expectType<WritableStream<Uint8Array<ArrayBuffer>>>(stream.writable);
   expectError((stream.writable = 'd'));
 }
 
@@ -507,8 +508,8 @@ import { expectError, expectType } from 'tsd';
   let stream = new DecompressionStream('deflate');
   stream = new DecompressionStream('deflate-raw');
   stream = new DecompressionStream('gzip');
-  expectType<ReadableStream<Uint8Array>>(stream.readable);
+  expectType<ReadableStream<Uint8Array<ArrayBuffer>>>(stream.readable);
   expectError((stream.readable = 'd'));
-  expectType<WritableStream<Uint8Array>>(stream.writable);
+  expectType<WritableStream<Uint8Array<ArrayBuffer>>>(stream.writable);
   expectError((stream.writable = 'd'));
 }

types/cache-override.d.ts

@@ -37,8 +37,8 @@ declare module 'fastly:cache-override' {
      * to return the new body.
      */
     bodyTransformFn?: (
-      body: Uint8Array,
-    ) => Uint8Array | PromiseLike<Uint8Array>;
+      body: Uint8Array<ArrayBuffer>,
+    ) => Uint8Array<ArrayBuffer> | PromiseLike<Uint8Array<ArrayBuffer>>;
   }
   /**
    * The cache override mode for a request

types/experimental.d.ts

@@ -46,7 +46,7 @@ declare module 'fastly:experimental' {
    * **Note**: Can only be used during build-time initialization, not when processing requests.
    * @experimental
    */
-  export function includeBytes(path: string): Uint8Array;
+  export function includeBytes(path: string): Uint8Array<ArrayBuffer>;
 
   /**
    * Whether or not to allow Dynamic Backends.

types/globals.d.ts

@@ -843,7 +843,7 @@ declare class TextEncoder {
    * UTF-8 encodes the `input` string and returns a `Uint8Array` containing the encoded bytes.
    * @param [input='an empty string'] The text to encode.
    */
-  encode(input?: string): Uint8Array;
+  encode(input?: string): Uint8Array<ArrayBuffer>;
   // /**
   //  * UTF-8 encodes the `src` string to the `dest` Uint8Array and returns an object
   //  * containing the read Unicode code units and written UTF-8 bytes.
@@ -998,7 +998,7 @@ declare interface Fastly {
    * @hidden
    * @experimental
    */
-  includeBytes(path: string): Uint8Array;
+  includeBytes(path: string): Uint8Array<ArrayBuffer>;
 }
 
 /**
@@ -1055,15 +1055,15 @@ declare class CompressionStream {
    * console.log(stream.readable instanceof ReadableStream); // true
    * ```
    */
-  readonly readable: ReadableStream<Uint8Array>;
+  readonly readable: ReadableStream<Uint8Array<ArrayBuffer>>;
   /**
    * @example
    * ```js
    * let stream = new CompressionStream("gzip");
    * console.log(stream.writable instanceof WritableStream); // true
    * ```
    */
-  readonly writable: WritableStream<Uint8Array>;
+  readonly writable: WritableStream<Uint8Array<ArrayBuffer>>;
 }
 
 /**
@@ -1110,15 +1110,15 @@ declare class DecompressionStream {
    * console.log(stream.readable instanceof ReadableStream); // true
    * ```
    */
-  readonly readable: ReadableStream<Uint8Array>;
+  readonly readable: ReadableStream<Uint8Array<ArrayBuffer>>;
   /**
    * @example
    * ```js
    * let stream = new DecompressionStream("gzip");
    * console.log(stream.writable instanceof WritableStream); // true
    * ```
    */
-  readonly writable: WritableStream<Uint8Array>;
+  readonly writable: WritableStream<Uint8Array<ArrayBuffer>>;
 }
 
 // Note: the contents below here are, partially modified, copies of content from TypeScript's
@@ -1175,7 +1175,7 @@ interface Blob {
   /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/Blob/slice) */
   slice(start?: number, end?: number, contentType?: string): Blob;
   /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/Blob/stream) */
-  stream(): ReadableStream<Uint8Array>;
+  stream(): ReadableStream<Uint8Array<ArrayBuffer>>;
   /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/Blob/text) */
   text(): Promise<string>;
 }
@@ -1265,7 +1265,7 @@ declare type XMLHttpRequestBodyInit =
  * @group Fetch API
  */
 declare interface Body {
-  readonly body: ReadableStream<Uint8Array> | null;
+  readonly body: ReadableStream<Uint8Array<ArrayBuffer>> | null;
   readonly bodyUsed: boolean;
   arrayBuffer(): Promise<ArrayBuffer>;
   blob(): Promise<Blob>;

types/secret-store.d.ts

@@ -39,6 +39,6 @@ declare module 'fastly:secret-store' {
      *       always avoid using this method when possible, instead passing
      *       the secret directly.
      */
-    rawBytes(): Uint8Array;
+    rawBytes(): Uint8Array<ArrayBuffer>;
   }
 }