Show the spending tx of outpoints with electrum 1.5

app/api/electrumAddressApi.js

@@ -353,6 +353,34 @@ function lookupTxBlockHash(txid) {
 	});
 }
 
+// Lookup the spending transaction and height of a given transaction output. Only works with Electrum 1.5 protocol, ElectRS 0.9.0 does not implement subscriptions
+// but can return the transaction spending the given outpoint
+
+function lookupOutpointTx(txid, vout) {
+	if (electrumClients.length == 0) {
+		return Promise.reject({ error: "Not supported by Electrum 1.4", userText: noConnectionsErrorText });
+	}
+
+	return runOnAllServers(function(electrumClient) {
+		return electrumClient.request('blockchain.outpoint.subscribe', [txid, vout]);
+	}).then(function(results) {
+		var spend_infos = results[0].result;
+		runOnAllServers(function(electrumClient) {
+			return electrumClient.request('blockchain.outpoint.unsubscribe', [txid, vout]) //will fail until subscriptions for outpoint are implemented in ElectRS
+		});
+		if (results.slice(1).every(({ result }) => result == spend_infos)) {
+			if (spend_infos.length < 2) {
+				return false;
+			} else {
+				return spend_infos;
+			}
+		} else {
+			return Promise.reject({conflictedResults:results});
+		}
+	});
+}
+
+
 function logStats(cmd, dt, success) {
 	if (!global.electrumStats.rpc[cmd]) {
 		global.electrumStats.rpc[cmd] = {count:0, time:0, successes:0, failures:0};
@@ -380,5 +408,6 @@ module.exports = {
 	connectToServers: connectToServers,
 	getAddressDetails: getAddressDetails,
 	lookupTxBlockHash: lookupTxBlockHash,
+	lookupOutpointTx: lookupOutpointTx,
 };
 

routes/baseRouter.js

@@ -26,6 +26,7 @@ const coins = require("./../app/coins.js");
 const config = require("./../app/config.js");
 const coreApi = require("./../app/api/coreApi.js");
 const addressApi = require("./../app/api/addressApi.js");
+const electrumAddressApi = require("./../app/api/electrumAddressApi.js");
 const rpcApi = require("./../app/api/rpcApi.js");
 const btcQuotes = require("./../app/coins/btcQuotes.js");
 
@@ -1423,6 +1424,25 @@ router.get("/tx/:transactionId", asyncHandler(async (req, res, next) => {
 
 		await Promise.all(promises);
 
+		// Electrs 0.9.0 support spending transaction lookup for an outpoint
+		if ((config.addressApi == "electrum" || config.addressApi == "electrumx")  && config.electrumTxIndex) {
+			let spending_promises = [];
+			for (const vout in tx.vout) {
+				spending_promises.push(new Promise(async (resolve, reject) => {
+					if (res.locals.utxos[vout] == null) {
+						const spent = await electrumAddressApi.lookupOutpointTx(txid, parseInt(vout));
+						resolve(spent);
+					} else {
+						resolve(false);
+					}
+				}));
+			}
+
+			await Promise.all(spending_promises).then((outpoint_results) => {
+				res.locals.spendings = outpoint_results;
+			});
+		}
+
 		if (global.specialTransactions && global.specialTransactions[txid]) {
 			let funInfo = global.specialTransactions[txid];
 

views/includes/transaction-io-details.pug

@@ -46,7 +46,7 @@ mixin outputValueDisplay(vout, voutIndex)
 			if (utxos[voutIndex])
 				span(title="This output remains unspent (a valid UTXO)." data-bs-toggle="tooltip")
 					i.far.fa-check-circle.fa-sm.text-success.ms-2
-
+					
 			else if (utxos[voutIndex] == null)
 				span(title="This output has been spent (destroyed)." data-bs-toggle="tooltip")
 					i.far.fa-times-circle.fa-sm.text-danger.ms-2
@@ -290,10 +290,22 @@ mixin outputValueDisplay(vout, voutIndex)
 									+darkBadge
 										span(title=`Output Type: ${utils.outputTypeName(vout.scriptPubKey.type)}`, data-bs-toggle="tooltip") #{utils.outputTypeAbbreviation(vout.scriptPubKey.type)}
 
+						if (spendings)
+							- var spending_txid = spendings[voutIndex].spender_txhash;
+							if (spending_txid)
+								span.mt-1 spent by
+								a(href=`./tx/${spending_txid}`) #{utils.ellipsizeMiddle(spendings[voutIndex].spender_txhash,9)}
+								if (spendings[voutIndex].spender_height > 0 && spendings[voutIndex].spender_height > spendings[voutIndex].height)
+									span  #{spendings[voutIndex].spender_height - spendings[voutIndex].height} blocks later
+								else if (spendings[voutIndex].spender_height <= 0)
+									span  in the mempool
+								else if (spendings[voutIndex].spender_height == spendings[voutIndex].height)
+									span  in the same block
 
 					span.ms-2.float-end
 						+outputValueDisplay(vout, voutIndex)
 
+
 					if (vout && vout.scriptPubKey.asm && !vout.scriptPubKey.asm.startsWith("OP_RETURN "))
 						if (voutAddresses.length == 0)
 							.my-2.d-none.d-sm-block