From 21b1e35679800608480e2793a6a9b1604f33466a Mon Sep 17 00:00:00 2001
From: "Benjamin E. Coe" <bencoe@gmail.com>
Date: Sun, 26 Feb 2017 00:21:26 -0600
Subject: [PATCH] fix: running parse() multiple times on the same yargs
 instance caused exception if help() enabled (#790)

---
 test/command.js | 15 +++++++++++++++
 yargs.js        |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/test/command.js b/test/command.js
index 9396e144e..8c6df70bb 100644
--- a/test/command.js
+++ b/test/command.js
@@ -747,6 +747,21 @@ describe('Command', function () {
     counter.should.equal(2)
   })
 
+  // addresses: https://github.com/yargs/yargs/issues/776
+  it('allows command handler to be invoked repeatedly when help is enabled', function (done) {
+    var counter = 0
+    var y = yargs([])
+      .command('foo', 'the foo command', {}, function (argv) {
+        counter++
+      })
+      .help()
+    y.parse(['foo'], function () {})
+    y.parse(['foo'], function () {
+      counter.should.equal(2)
+      return done()
+    })
+  })
+
   // addresses https://github.com/yargs/yargs/issues/522
   it('does not require builder function to return', function () {
     var argv = yargs('yo')
diff --git a/yargs.js b/yargs.js
index d1ffd31a9..a1e351f76 100644
--- a/yargs.js
+++ b/yargs.js
@@ -967,7 +967,7 @@ function Yargs (processArgs, cwd, parentRequire) {
         // consider any multi-char helpOpt alias as a valid help command
         // unless all helpOpt aliases are single-char
         // note that parsed.aliases is a normalized bidirectional map :)
-        var helpCmds = [helpOpt].concat(aliases[helpOpt])
+        var helpCmds = [helpOpt].concat(aliases[helpOpt] || [])
         var multiCharHelpCmds = helpCmds.filter(function (k) {
           return k.length > 1
         })