refactor(vtransfer): transfer interceptor updates (#9470)

#8624 (comment)

packages/vats/src/transfer.js

@@ -31,13 +31,13 @@ const prepareTransferInterceptor = (zone, vowTools) => {
     'TransferInterceptorKit',
     {
       public: TargetAppI,
-      encodeAckWatcher: M.interface('EncodeAckWatcher', {
+      ackSender: M.interface('AckSender', {
         onFulfilled: ReactionGuard,
       }),
-      sendErrorWatcher: M.interface('SendErrorWatcher', {
+      nackSender: M.interface('NackSender', {
         onRejected: ReactionGuard,
       }),
-      logErrorWatcher: M.interface('LogErrorWatcher', {
+      errorLogger: M.interface('ErrorLogger', {
         onRejected: ReactionGuard,
       }),
     },
@@ -55,7 +55,7 @@ const prepareTransferInterceptor = (zone, vowTools) => {
     {
       public: {
         async receiveUpcall(obj) {
-          const { isActiveTap, tap, targetHost } = this.state;
+          const { isActiveTap, tap } = this.state;
 
           obj.type === VTRANSFER_IBC_EVENT ||
             Fail`Invalid upcall argument type ${obj.type}; expected ${bare(VTRANSFER_IBC_EVENT)}`;
@@ -67,64 +67,67 @@ const prepareTransferInterceptor = (zone, vowTools) => {
 
           // See if the upcall result needs special handling.
           if (obj.event === 'writeAcknowledgement') {
-            const ackMethodData = {
+            // Respond with the ack (or an active tap's replacement thereof).
+            const response = {
               type: 'IBC_METHOD',
               method: 'receiveExecuted',
               packet: obj.packet,
+              ack: obj.acknowledgement,
             };
-            if (isActiveTap) {
-              retP = watch(retP, this.facets.encodeAckWatcher, {
-                ackMethodData,
-              });
-            } else {
-              // This is a passive tap, so forward the ack without intervention.
-              ackMethodData.ack = obj.acknowledgement;
-              retP = watch(E(targetHost).sendDowncall(ackMethodData));
-            }
-            retP = watch(retP, this.facets.sendErrorWatcher, { ackMethodData });
+            const senderContext = { response, isActiveTap };
+            // An active tap must wait for the upcall result,
+            // but a passive tap can proceed immediately.
+            retP = isActiveTap
+              ? watch(retP, this.facets.ackSender, senderContext)
+              : /** @type {any} */ (
+                  E(this.facets.ackSender).onFulfilled(undefined, senderContext)
+                );
+            // Upon failure, respond with an error acknowledgement.
+            retP = watch(retP, this.facets.nackSender, { response });
           }
 
-          // Log errors in the upcall handling.
-          retP = watch(retP, this.facets.logErrorWatcher, { obj });
+          // Always log errors.
+          retP = watch(retP, this.facets.errorLogger, { obj });
 
-          if (isActiveTap) {
-            // If the tap is active, return the promiseVow to the caller.  This
-            // will delay the middleware until fulfilment of the retP chain.
-            return retP;
-          }
-
-          // Otherwise, passively return nothing.
+          // For an active tap, return a promise/vow to delay middleware
+          // until final settlement.
+          // For a passive tap, return undefined to skip such delays.
+          return isActiveTap ? retP : undefined;
         },
       },
       /**
-       * `watch` callback for encoding the raw `ack` return value from an active
-       * `writeAcknowledgement` tap as base64, then sending down to the
-       * targetHost.
+       * A watcher for sending acknowledgements down to the host.
        */
-      encodeAckWatcher: {
-        onFulfilled(rawAck, { ackMethodData }) {
-          // Encode the tap's ack and write it out.
-          const ack = byteSourceToBase64(coerceToByteSource(rawAck));
-          ackMethodData = { ...ackMethodData, ack };
-          return E(this.state.targetHost).sendDowncall(ackMethodData);
+      ackSender: {
+        onFulfilled(rawAck, { response, isActiveTap }) {
+          if (isActiveTap) {
+            // Incorporate an active tap's replacement ack.
+            const ack = byteSourceToBase64(coerceToByteSource(rawAck));
+            response = { ...response, ack };
+          }
+          return E(this.state.targetHost).sendDowncall(response);
         },
       },
+
       /**
-       * `watch` callback for handling errors in the sending of an ack and
-       * reifying it as an error acknowledgement.
+       * A watcher for sending error acknowledgements down to the host.
        */
-      sendErrorWatcher: {
-        onRejected(error, { ackMethodData }) {
+      nackSender: {
+        onRejected(error, { response }) {
           console.error(`Error sending ack:`, error);
           const rawAck = JSON.stringify({ error: error.message });
-          ackMethodData = { ...ackMethodData, ack: byteSourceToBase64(rawAck) };
-          return E(this.state.targetHost).sendDowncall(ackMethodData);
+          const nack = { ...response, ack: byteSourceToBase64(rawAck) };
+          return E(this.state.targetHost).sendDowncall(nack);
         },
       },
-      /** `watch` callback for logging errors in the upcall handling. */
-      logErrorWatcher: {
+
+      /**
+       * A watcher for logging errors.
+       */
+      errorLogger: {
         onRejected(error, { obj }) {
           console.error(`Error in handling of`, obj, error);
+          // Don't propagate the error any further.
         },
       },
     },