Fix TypeScript 5.9 compatibility issues with BufferSource types

Problem

GitHub Actions workflows are failing due to type errors after Deno automatically upgraded to version 2.5, which includes TypeScript 5.9.2. The type errors occur when passing Uint8Array<ArrayBufferLike> to functions expecting BufferSource.

Error details

The following type errors are occurring in packages/fedify/src/runtime/key.ts:

Argument of type 'Uint8Array<ArrayBufferLike>' is not assignable to parameter of type 'BufferSource'.
  Type 'Uint8Array<ArrayBufferLike>' is not assignable to type 'ArrayBufferView<ArrayBuffer>'.
    Types of property 'buffer' are incompatible.
      Type 'ArrayBufferLike' is not assignable to type 'ArrayBuffer'.
        Type 'SharedArrayBuffer' is missing the following properties from type 'ArrayBuffer': 
        resizable, resize, detached, transfer, transferToFixedLength

Affected lines:

Line 42: crypto.subtle.importKey() with "pkcs8" format
Line 114: crypto.subtle.importKey() with "spki" format
Line 122: crypto.subtle.importKey() with "raw" format

Root cause

Deno 2.5 upgraded TypeScript from 5.8.3 to 5.9.2
TypeScript 5.9 includes changes to lib.d.ts that make ArrayBufferLike and ArrayBuffer types incompatible
The new ArrayBuffer type in TypeScript 5.9 includes additional properties that SharedArrayBuffer doesn't have

Solution

Instead of downgrading Deno, we should fix the type compatibility issues properly. The Uint8Array instances need to be cast or ensured to use ArrayBuffer instead of ArrayBufferLike when passed to Web Crypto API methods.

References

Line 36 was also affected. I'd like to handle this issue.

Currently, I'm working on this branch: https://github.com/dodok8/fedify/tree/dodok8-issue-399

However, federation/kv.test.ts is failing on my local machine

  await t.step("set() & get()", async () => {
    await store.set(["foo", "bar"], "foobar");
    assertEquals(await store.get(["foo", "bar"]), "foobar");
    assertEquals(await store.get(["foo"]), undefined);

    await store.set(["foo", "baz"], "baz", {
      ttl: Temporal.Duration.from({ seconds: 0 }),
    });
    assertEquals(await store.get(["foo", "baz"]), undefined);
  });

assertEquals(await store.get(["foo", "baz"]), undefined); failed with value "baz", which means the ttl options don't work properly. It's another issue anyway; it makes the test fail.

EDIT: After adding await new Promise((resolve) => setTimeout(resolve, 1000)); between 15 and 16, the overall test passed.

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Fix TypeScript 5.9 compatibility issues with `BufferSource` types #423

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Fix TypeScript 5.9 compatibility issues with BufferSource types #423

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dodok8 commented on Sep 11, 2025

dodok8 commented on Sep 11, 2025

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Fix TypeScript 5.9 compatibility issues with `BufferSource` types #423