net: check and throw on error for getsockname

This commit attempts fix a TODO in net.js:
TODO(bnoordhuis) Check err and throw?

PR-URL: https://github.com/nodejs/node/pull/12871
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/net.js

@@ -1473,8 +1473,10 @@ Object.defineProperty(Server.prototype, 'listening', {
 Server.prototype.address = function() {
   if (this._handle && this._handle.getsockname) {
     var out = {};
-    this._handle.getsockname(out);
+    var err = this._handle.getsockname(out);
-    // TODO(bnoordhuis) Check err and throw?
+    if (err) {
+      throw errnoException(err, 'address');
+    }
     return out;
   } else if (this._pipeName) {
     return this._pipeName;

test/parallel/test-socket-address.js

@@ -0,0 +1,17 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+
+// This tests checks that if server._handle.getsockname
+// returns an error number, an error is thrown.
+
+const server = net.createServer({});
+server.listen(0, common.mustCall(function() {
+  server._handle.getsockname = function(out) {
+    return -1;
+  };
+  assert.throws(() => this.address(),
+                /^Error: address ([\w|\s-\d])+$/);
+  server.close();
+}));