fix(socks5): preserve dispatch backpressure return value

lib/dispatcher/socks5-proxy-agent.js

@@ -173,7 +173,7 @@ class Socks5ProxyAgent extends DispatcherBase {
   /**
    * Dispatch a request through the SOCKS5 proxy
    */
-  async [kDispatch] (opts, handler) {
+  [kDispatch] (opts, handler) {
     const { origin } = opts
 
     debug('dispatching request to', origin, 'via SOCKS5')
@@ -230,8 +230,12 @@ class Socks5ProxyAgent extends DispatcherBase {
       return pool[kDispatch](opts, handler)
     } catch (err) {
       debug('dispatch error:', err)
-      if (typeof handler.onError === 'function') {
+      if (typeof handler.onResponseError === 'function') {
+        handler.onResponseError(null, err)
+        return false
+      } else if (typeof handler.onError === 'function') {
         handler.onError(err)
+        return false
       } else {
         throw err
       }

test/socks5-proxy-agent.js

@@ -84,6 +84,28 @@ test('Socks5ProxyAgent - uses custom connector for proxy connection', async (t)
   await p.completed
 })
 
+test('Socks5ProxyAgent - dispatch returns boolean backpressure signal', async (t) => {
+  const p = tspl(t, { plan: 1 })
+  const proxyWrapper = new Socks5ProxyAgent('socks5://localhost:9999')
+
+  const ret = proxyWrapper.dispatch({
+    origin: 'http://example.com',
+    path: '/',
+    method: 'GET'
+  }, {
+    onRequestStart () {},
+    onResponseStart () {},
+    onResponseData () {},
+    onResponseEnd () {},
+    onResponseError () {}
+  })
+
+  p.equal(typeof ret, 'boolean')
+
+  await proxyWrapper.destroy()
+  await p.completed
+})
+
 test('Socks5ProxyAgent - basic HTTP connection', async (t) => {
   const p = tspl(t, { plan: 2 })