fix(plugin-gateway): read the optional ids of a message as null like discord.js

.changeset/gateway-message-null-ids.md

@@ -0,0 +1,5 @@
+---
+"@wolfstar/plugin-gateway": patch
+---
+
+`Message#webhookId`, `applicationId`, `nonce` and `position` are `null` when the message has none, like discord.js, instead of the `undefined` they inherited from `@discordjs/structures`, so a check such as `message.webhookId !== null` no longer takes every message for the one of a webhook.

packages/plugin-gateway/src/structures/messages/Message.ts

@@ -178,7 +178,11 @@ export type MessageSnapshot = Partialize<
  * the checks answer a promise read from the cache, typed as one once `GatewayCacheConfig` declares the cache
  * asynchronous. The `fetch*able()` twins also ask the API for what is not cached.
  */
-export class Message<InGuild extends boolean = boolean> extends BaseMessage<""> {
+// The IDs `@discordjs/structures` reads as `undefined` when the message has none, where discord.js gives `null`: omitted
+// from its data type so `Message` can override them.
+type NullableMessageKeys = "webhook_id" | "application_id" | "nonce" | "position";
+
+export class Message<InGuild extends boolean = boolean> extends BaseMessage<NullableMessageKeys> {
   /**
    * Keeps the raw `timestamp` and `edited_timestamp`, which `@discordjs/structures` strips and re-serializes in its own
    * format, so that {@link Message.toJSON} returns the message as received.
@@ -490,6 +494,34 @@ export class Message<InGuild extends boolean = boolean> extends BaseMessage<"">
     return this.optimizedTimestamp("edited_timestamp");
   }
 
+  /**
+   * The ID of the webhook that sent the message, `null` when no webhook did, like discord.js's `Message#webhookId`.
+   */
+  public override get webhookId(): string | null {
+    return this[kData].webhook_id ?? null;
+  }
+
+  /**
+   * The ID of the application of an interaction or of a Rich Presence-related chat embed, `null` without one.
+   */
+  public override get applicationId(): string | null {
+    return this[kData].application_id ?? null;
+  }
+
+  /**
+   * The nonce the message was sent with, to check that it was sent, `null` without one.
+   */
+  public override get nonce(): string | number | null {
+    return this[kData].nonce ?? null;
+  }
+
+  /**
+   * The approximate position of the message in a thread, `null` outside of one.
+   */
+  public override get position(): number | null {
+    return this[kData].position ?? null;
+  }
+
   public get editedAt(): Date | null {
     const { editedTimestamp } = this;
     return editedTimestamp === null ? null : new Date(editedTimestamp);

packages/plugin-gateway/tests/structures.test.ts

@@ -342,6 +342,32 @@ describe("optimized structures", () => {
     expect(clone.toJSON().joined_at).toBe("2026-01-01T00:00:00.000Z");
   });
 
+  test("GIVEN a message without a webhook, an application, a nonce or a position THEN they are null like discord.js", () => {
+    const message = new Message({ id: "1", channel_id: "2", author: data } as never);
+
+    expect(message.webhookId).toBeNull();
+    expect(message.applicationId).toBeNull();
+    expect(message.nonce).toBeNull();
+    expect(message.position).toBeNull();
+  });
+
+  test("GIVEN a message with a webhook, an application, a nonce and a position THEN they are read from it", () => {
+    const message = new Message({
+      id: "1",
+      channel_id: "2",
+      author: data,
+      webhook_id: "3",
+      application_id: "4",
+      nonce: "5",
+      position: 0,
+    } as never);
+
+    expect(message.webhookId).toBe("3");
+    expect(message.applicationId).toBe("4");
+    expect(message.nonce).toBe("5");
+    expect(message.position).toBe(0);
+  });
+
   test("GIVEN a message edit and permission overwrite THEN optimized values follow patches", () => {
     const message = new Message({
       id: "1",