setup a generic type (DRY)

packages/core/src/lib/light_push/index.ts

@@ -6,6 +6,7 @@ import {
   Libp2p,
   ProtocolCreateOptions,
   ProtocolError,
+  ProtocolResult,
   SendResult
 } from "@waku/interfaces";
 import { PushResponse } from "@waku/proto";
@@ -28,15 +29,7 @@ const log = new Logger("light-push");
 export const LightPushCodec = "/vac/waku/lightpush/2.0.0-beta1";
 export { PushResponse };
 
-type PreparePushMessageResult =
-  | {
-      query: PushRpc;
-      error: null;
-    }
-  | {
-      query: null;
-      error: ProtocolError;
-    };
+type PreparePushMessageResult = ProtocolResult<"query", PushRpc>;
 
 /**
  * Implements the [Waku v2 Light Push protocol](https://rfc.vac.dev/spec/19/).

packages/interfaces/src/metadata.ts

@@ -3,19 +3,11 @@ import type { PeerId } from "@libp2p/interface";
 import type { ShardInfo } from "./enr.js";
 import type {
   IBaseProtocol,
-  ProtocolError,
+  ProtocolResult,
   ShardingParams
 } from "./protocols.js";
 
-export type QueryResult =
-  | {
-      shardInfo: ShardInfo;
-      error: null;
-    }
-  | {
-      shardInfo: null;
-      error: ProtocolError;
-    };
+export type QueryResult = ProtocolResult<"shardInfo", ShardInfo>;
 
 // IMetadata always has shardInfo defined while it is optionally undefined in IBaseProtocol
 export interface IMetadata extends Omit<IBaseProtocol, "shardInfo"> {

packages/interfaces/src/protocols.ts

@@ -97,6 +97,16 @@ export type Callback<T extends IDecodedMessage> = (
   msg: T
 ) => void | Promise<void>;
 
+// K = key name
+// T = value type
+export type ProtocolResult<K extends string, T> =
+  | ({
+      [key in K]: T;
+    } & { error: null })
+  | ({
+      [key in K]: null;
+    } & { error: ProtocolError });
+
 export enum ProtocolError {
   /** Could not determine the origin of the fault. Best to check connectivity and try again */
   GENERIC_FAIL = "Generic error",