feat: allow for duplicate messages (ChainSafe#402)

src/index.ts

@@ -109,6 +109,8 @@ export interface GossipsubOpts extends GossipsubOptsSpec, PubSubInit {
   asyncValidation: boolean
   /** Do not throw `InsufficientPeers` error if publishing to zero peers */
   allowPublishToZeroPeers: boolean
+  /** Do not throw `PublishError.Duplicate` if publishing duplicate messages */
+  allowPublishDuplicates: boolean
   /** For a single stream, await processing each RPC before processing the next */
   awaitRpcHandler: boolean
   /** For a single RPC, await processing each message before processing the next */
@@ -2013,7 +2015,10 @@ export class GossipSub extends EventEmitter<GossipsubEvents> implements PubSub<G
     const msgId = await this.msgIdFn(msg)
     const msgIdStr = this.msgIdToStrFn(msgId)
 
-    if (this.seenCache.has(msgIdStr)) {
+    // Current publish opt takes precedence global opts, while preserving false value
+    const allowPublishDuplicates = opts?.allowPublishDuplicates ?? this.opts.allowPublishDuplicates
+
+    if (this.seenCache.has(msgIdStr) && !allowPublishDuplicates) {
       // This message has already been seen. We don't re-publish messages that have already
       // been published on the network.
       throw Error('PublishError.Duplicate')

src/types.ts

@@ -74,6 +74,7 @@ export enum SignaturePolicy {
 
 export type PublishOpts = {
   allowPublishToZeroPeers?: boolean
+  allowPublishDuplicates?: boolean
 }
 
 export enum PublishConfigType {