Fix reporting of abort errors in Node v20, where there may be multiple

Author: pimterry

custom-typings/node-type-extensions.d.ts

@@ -112,4 +112,8 @@ declare module "http2" {
         __lastHopConnectAddress?: net.Socket['__lastHopConnectAddress'];
         __timingInfo?: net.Socket['__timingInfo'];
     }
+}
+
+declare class AggregateError extends Error {
+    errors: Error[]
 }

src/rules/requests/request-handlers.ts

@@ -1013,9 +1013,13 @@ export class PassThroughHandler extends PassThroughHandlerDefinition {
                     // connection-level issue, so we try to create connection issues downstream.
                     resetOrDestroy(clientReq);
 
-                    throw new AbortError(`Upstream connection error: ${
-                        e.message ?? e
-                    }`, e.code);
+                    // Aggregate errors can be thrown if multiple (IPv4/6) addresses were tested. Note that
+                    // AggregateError only exists in Node 15+. If that happens, we need to combine errors:
+                    const errorMessage = typeof AggregateError !== 'undefined' && (e instanceof AggregateError)
+                        ? e.errors.map(e => e.message).join(', ')
+                        : (e.message ?? e.code ?? e);
+
+                    throw new AbortError(`Upstream connection error: ${errorMessage}`, e.code);
                 } else {
                     e.statusCode = 502;
                     e.statusMessage = 'Error communicating with upstream server';

test/integration/subscriptions/response-events.spec.ts

@@ -473,7 +473,8 @@ describe("Abort subscriptions", () => {
 
                 expect(seenAbort.error!.message).to.be.oneOf([
                     'Upstream connection error: connect ECONNREFUSED 127.0.0.1:8999',
-                    'Upstream connection error: connect ECONNREFUSED ::1:8999'
+                    'Upstream connection error: connect ECONNREFUSED ::1:8999',
+                    'Upstream connection error: connect ECONNREFUSED ::1:8999, connect ECONNREFUSED 127.0.0.1:8999'
                 ]);
                 expect(seenAbort.error!.code).to.equal('ECONNREFUSED');
             });