net: fix net.Server.prototype.listen error message

lib/net.js

@@ -1416,7 +1416,7 @@ Server.prototype.listen = function() {
     return this;
   }
 
-  throw new Error('Invalid listen argument: ' + options);
+  throw new Error('Invalid listen argument: ' + util.inspect(options));
 };
 
 function lookupAndListen(self, port, address, backlog, exclusive) {

test/parallel/test-net-server-listen-options.js

@@ -0,0 +1,81 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+const util = require('util');
+
+function close() { this.close(); }
+
+function listenError(literals, ...values) {
+  let result = literals[0];
+  for (const [i, value] of values.entries()) {
+    const str = util.inspect(value);
+    // Need to escape special characters.
+    result += str.replace(/[\\^$.*+?()[\]{}|=!<>:-]/g, '\\$&');
+    result += literals[i + 1];
+  }
+  return new RegExp(`Error: Invalid listen argument: ${result}`);
+}
+
+{
+  // Test listen()
+  net.createServer().listen().on('listening', common.mustCall(close));
+  // Test listen(cb)
+  net.createServer().listen(common.mustCall(close));
+}
+
+// Test listen(port, cb) and listen({port: port}, cb) combinations
+const listenOnPort = [
+  (port, cb) => net.createServer().listen({port}, cb),
+  (port, cb) => net.createServer().listen(port, cb)
+];
+
+{
+  const portError = /^RangeError: "port" argument must be >= 0 and < 65536$/;
+  for (const listen of listenOnPort) {
+    // Arbitrary unused ports
+    listen('0', common.mustCall(close));
+    listen(0, common.mustCall(close));
+    listen(undefined, common.mustCall(close));
+    // Test invalid ports
+    assert.throws(() => listen(-1, common.mustNotCall()), portError);
+    assert.throws(() => listen(NaN, common.mustNotCall()), portError);
+    assert.throws(() => listen(123.456, common.mustNotCall()), portError);
+    assert.throws(() => listen(65536, common.mustNotCall()), portError);
+    assert.throws(() => listen(1 / 0, common.mustNotCall()), portError);
+    assert.throws(() => listen(-1 / 0, common.mustNotCall()), portError);
+  }
+  // In listen(options, cb), port takes precedence over path
+  assert.throws(() => {
+    net.createServer().listen({ port: -1, path: common.PIPE },
+                              common.mustNotCall());
+  }, portError);
+}
+
+{
+  function shouldFailToListen(options, optionsInMessage) {
+    // Plain arguments get normalized into an object before
+    // formatted in message, options objects don't.
+    if (arguments.length === 1) {
+      optionsInMessage = options;
+    }
+    const block = () => {
+      net.createServer().listen(options, common.mustNotCall());
+    };
+    assert.throws(block, listenError`${optionsInMessage}`,
+                  `expect listen(${util.inspect(options)}) to throw`);
+  }
+
+  shouldFailToListen(null, { port: null });
+  shouldFailToListen({ port: null });
+  shouldFailToListen(false, { port: false });
+  shouldFailToListen({ port: false });
+  shouldFailToListen(true, { port: true });
+  shouldFailToListen({ port: true });
+  // Invalid fd as listen(handle)
+  shouldFailToListen({ fd: -1 });
+  // Invalid path in listen(options)
+  shouldFailToListen({ path: -1 });
+  // Host without port
+  shouldFailToListen({ host: 'localhost' });
+}