fix: make port transferables unique

packages/ipfs-message-port-client/README.md

@@ -102,7 +102,7 @@ values instead of copying.
 
 > **Note:** Transferring data will empty it on the sender side which can lead to
 > errors if that data is used again later. To avoid these errors transfer option
-> was added so user can explicitily give up reference when it is safe to do so.
+> was added so user can explicitly give up reference when it is safe to do so.
 
 ```js
 /**
@@ -115,7 +115,7 @@ const example = async (data) => {
 }
 ```
 
-It is however recommended to prefer web native [Blob][] / [File][] intances as
+It is however recommended to prefer web native [Blob][] / [File][] instances as
 most web APIs provide them as option & can be send across without copying
 underlying memory.
 

packages/ipfs-message-port-client/src/client/transport.js

@@ -178,7 +178,7 @@ module.exports = class MessageTransport {
         input: query.toJSON()
       },
       // @ts-ignore - TS seems to want second arg to postMessage to not be undefined
-      query.transfer()
+      [...new Set(query.transfer() || [])]
     )
   }
 

packages/ipfs-message-port-protocol/src/core.js

@@ -197,7 +197,7 @@ const decodeCallback = ({ port }) => {
    * @returns {void}
    */
   const callback = (args, transfer = []) => {
-    port.postMessage(args, transfer)
+    port.postMessage(args, [...new Set(transfer)])
   }
 
   return callback

packages/ipfs-message-port-server/src/server.js

@@ -212,9 +212,12 @@ exports.Server = class Server {
     if (!query.signal.aborted) {
       try {
         const value = await query.result
+        const transfer = [...new Set(value.transfer || [])]
+        delete value.transfer
+
         port.postMessage(
           { type: 'result', id, result: { ok: true, value } },
-          value.transfer || []
+          transfer
         )
       } catch (error) {
         port.postMessage({