feat: Expose meta field and ensure encoder sets it

src/codec.spec.ts

@@ -3,6 +3,7 @@ import {
   createEncoder,
   DecodedMessage,
 } from "@waku/core/lib/message/version_0";
+import type { IProtoMessage } from "@waku/interfaces";
 import {
   generatePrivateKey,
   generateSymmetricKey,
@@ -32,6 +33,15 @@ import * as rln from "./index.js";
 const TestContentTopic = "/test/1/waku-message/utf8";
 const EMPTY_PUBSUB_TOPIC = "";
 
+const EMPTY_PROTO_MESSAGE = {
+  timestamp: undefined,
+  contentTopic: "",
+  ephemeral: undefined,
+  meta: undefined,
+  rateLimitProof: undefined,
+  version: undefined,
+};
+
 describe("RLN codec with version 0", () => {
   it("toWire", async function () {
     const rlnInstance = await rln.create();
@@ -352,3 +362,110 @@ describe("RLN Codec - epoch", () => {
     expect(msg.timestamp).to.not.be.undefined;
   });
 });
+
+describe("RLN codec with version 0 and meta setter", () => {
+  // Encode the length of the payload
+  // Not a relevant real life example
+  const metaSetter = (msg: IProtoMessage & { meta: undefined }): Uint8Array => {
+    const buffer = new ArrayBuffer(4);
+    const view = new DataView(buffer);
+    view.setUint32(0, msg.payload.length, false);
+    return new Uint8Array(buffer);
+  };
+
+  it("toWire", async function () {
+    const rlnInstance = await rln.create();
+    const credential = rlnInstance.generateIdentityCredentials();
+    const index = 0;
+    const payload = new Uint8Array([1, 2, 3, 4, 5]);
+
+    rlnInstance.insertMember(credential.IDCommitment);
+
+    const rlnEncoder = createRLNEncoder({
+      encoder: createEncoder({ contentTopic: TestContentTopic, metaSetter }),
+      rlnInstance,
+      index,
+      credential,
+    });
+    const rlnDecoder = createRLNDecoder({
+      rlnInstance,
+      decoder: createDecoder(TestContentTopic),
+    });
+
+    const bytes = await rlnEncoder.toWire({ payload });
+
+    expect(bytes).to.not.be.undefined;
+    const protoResult = await rlnDecoder.fromWireToProtoObj(bytes!);
+    expect(protoResult).to.not.be.undefined;
+    const msg = (await rlnDecoder.fromProtoObj(
+      EMPTY_PUBSUB_TOPIC,
+      protoResult!
+    ))!;
+
+    const expectedMeta = metaSetter({
+      ...EMPTY_PROTO_MESSAGE,
+      payload: protoResult!.payload,
+    });
+
+    expect(msg!.meta).to.deep.eq(expectedMeta);
+
+    expect(msg.rateLimitProof).to.not.be.undefined;
+    expect(msg.verify([rlnInstance.getMerkleRoot()])).to.be.true;
+    expect(msg.verifyNoRoot()).to.be.true;
+    expect(msg.epoch).to.not.be.undefined;
+    expect(msg.epoch).to.be.gt(0);
+
+    expect(msg.contentTopic).to.eq(TestContentTopic);
+    expect(msg.msg.version).to.eq(0);
+    expect(msg.payload).to.deep.eq(payload);
+    expect(msg.timestamp).to.not.be.undefined;
+  });
+
+  it("toProtoObj", async function () {
+    const rlnInstance = await rln.create();
+    const credential = rlnInstance.generateIdentityCredentials();
+    const index = 0;
+    const payload = new Uint8Array([1, 2, 3, 4, 5]);
+
+    rlnInstance.insertMember(credential.IDCommitment);
+
+    const rlnEncoder = new RLNEncoder(
+      createEncoder({ contentTopic: TestContentTopic, metaSetter }),
+      rlnInstance,
+      index,
+      credential
+    );
+    const rlnDecoder = new RLNDecoder(
+      rlnInstance,
+      createDecoder(TestContentTopic)
+    );
+
+    const proto = await rlnEncoder.toProtoObj({ payload });
+
+    expect(proto).to.not.be.undefined;
+    const msg = (await rlnDecoder.fromProtoObj(
+      EMPTY_PUBSUB_TOPIC,
+      proto!
+    )) as RlnMessage<DecodedMessage>;
+
+    const expectedMeta = metaSetter({
+      ...EMPTY_PROTO_MESSAGE,
+      payload: msg!.payload,
+    });
+
+    expect(msg!.meta).to.deep.eq(expectedMeta);
+
+    expect(msg).to.not.be.undefined;
+    expect(msg.rateLimitProof).to.not.be.undefined;
+
+    expect(msg.verify([rlnInstance.getMerkleRoot()])).to.be.true;
+    expect(msg.verifyNoRoot()).to.be.true;
+    expect(msg.epoch).to.not.be.undefined;
+    expect(msg.epoch).to.be.gt(0);
+
+    expect(msg.contentTopic).to.eq(TestContentTopic);
+    expect(msg.msg.version).to.eq(0);
+    expect(msg.payload).to.deep.eq(payload);
+    expect(msg.timestamp).to.not.be.undefined;
+  });
+});

src/index.spec.ts

@@ -113,6 +113,7 @@ describe("js-rln", () => {
       console.log(err);
     }
   });
+
   it("should generate the same membership key if the same seed is provided", async function () {
     const rlnInstance = await rln.create();
     const seed = "This is a test seed";

src/message.ts

@@ -57,6 +57,10 @@ export class RlnMessage<T extends IDecodedMessage> implements IDecodedMessage {
     return this.msg.ephemeral;
   }
 
+  get meta(): Uint8Array | undefined {
+    return this.msg.meta;
+  }
+
   get epoch(): number | undefined {
     const bytes = this.msg.rateLimitProof?.epoch;
     if (!bytes) return;