node_modules

1 files changed, 357 insertions, 267 deletions

diff --git a/node_modules/yargs/yargs.js b/node_modules/yargs/yargs.js
index a63c94a4b..078bf8f14 100644
--- a/node_modules/yargs/yargs.js
+++ b/node_modules/yargs/yargs.js
@@ -1,3 +1,4 @@
+const argsert = require('./lib/argsert')
 const assign = require('./lib/assign')
 const Command = require('./lib/command')
 const Completion = require('./lib/completion')
@@ -8,6 +9,8 @@ const Validation = require('./lib/validation')
 const Y18n = require('y18n')
 const objFilter = require('./lib/obj-filter')
 const setBlocking = require('set-blocking')
+const applyExtends = require('./lib/apply-extends')
+const YError = require('./lib/yerror')
 
 var exports = module.exports = Yargs
 function Yargs (processArgs, cwd, parentRequire) {
@@ -65,23 +68,23 @@ function Yargs (processArgs, cwd, parentRequire) {
     // logic is used to build a nested command
     // hierarchy.
     var tmpOptions = {}
-    tmpOptions.global = options.global ? options.global : []
+    tmpOptions.local = options.local ? options.local : []
     tmpOptions.configObjects = options.configObjects ? options.configObjects : []
 
-    // if a key has been set as a global, we
-    // do not want to reset it or its aliases.
-    var globalLookup = {}
-    tmpOptions.global.forEach(function (g) {
-      globalLookup[g] = true
-      ;(aliases[g] || []).forEach(function (a) {
-        globalLookup[a] = true
+    // if a key has been explicitly set as local,
+    // we should reset it before passing options to command.
+    var localLookup = {}
+    tmpOptions.local.forEach(function (l) {
+      localLookup[l] = true
+      ;(aliases[l] || []).forEach(function (a) {
+        localLookup[a] = true
       })
     })
 
-    // preserve groups containing global keys
+    // preserve all groups not set to local.
     preservedGroups = Object.keys(groups).reduce(function (acc, groupName) {
       var keys = groups[groupName].filter(function (key) {
-        return key in globalLookup
+        return !(key in localLookup)
       })
       if (keys.length > 0) {
         acc[groupName] = keys
@@ -103,13 +106,13 @@ function Yargs (processArgs, cwd, parentRequire) {
 
     arrayOptions.forEach(function (k) {
       tmpOptions[k] = (options[k] || []).filter(function (k) {
-        return globalLookup[k]
+        return !localLookup[k]
       })
     })
 
     objectOptions.forEach(function (k) {
       tmpOptions[k] = objFilter(options[k], function (k, v) {
-        return globalLookup[k]
+        return !localLookup[k]
       })
     })
 
@@ -118,12 +121,11 @@ function Yargs (processArgs, cwd, parentRequire) {
 
     // if this is the first time being executed, create
     // instances of all our helpers -- otherwise just reset.
-    usage = usage ? usage.reset(globalLookup) : Usage(self, y18n)
-    validation = validation ? validation.reset(globalLookup) : Validation(self, usage, y18n)
+    usage = usage ? usage.reset(localLookup) : Usage(self, y18n)
+    validation = validation ? validation.reset(localLookup) : Validation(self, usage, y18n)
     command = command ? command.reset() : Command(self, usage, validation)
     if (!completion) completion = Completion(self, usage, command)
 
-    strict = false
     completionCommand = null
     output = ''
     exitError = null
@@ -171,56 +173,143 @@ function Yargs (processArgs, cwd, parentRequire) {
     frozen = undefined
   }
 
-  self.boolean = function (bools) {
-    options.boolean.push.apply(options.boolean, [].concat(bools))
+  self.boolean = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('boolean', keys)
     return self
   }
 
-  self.array = function (arrays) {
-    options.array.push.apply(options.array, [].concat(arrays))
+  self.array = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('array', keys)
     return self
   }
 
-  self.nargs = function (key, n) {
-    if (typeof key === 'object') {
-      Object.keys(key).forEach(function (k) {
-        self.nargs(k, key[k])
-      })
-    } else {
-      options.narg[key] = n
-    }
+  self.number = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('number', keys)
     return self
   }
 
-  self.number = function (numbers) {
-    options.number.push.apply(options.number, [].concat(numbers))
+  self.normalize = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('normalize', keys)
     return self
   }
 
-  self.choices = function (key, values) {
-    if (typeof key === 'object') {
-      Object.keys(key).forEach(function (k) {
-        self.choices(k, key[k])
-      })
-    } else {
-      options.choices[key] = (options.choices[key] || []).concat(values)
+  self.count = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('count', keys)
+    return self
+  }
+
+  self.string = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('string', keys)
+    return self
+  }
+
+  self.requiresArg = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('requiresArg', keys)
+    return self
+  }
+
+  self.skipValidation = function (keys) {
+    argsert('<array|string>', [keys], arguments.length)
+    populateParserHintArray('skipValidation', keys)
+    return self
+  }
+
+  function populateParserHintArray (type, keys, value) {
+    keys = [].concat(keys)
+    keys.forEach(function (key) {
+      options[type].push(key)
+    })
+  }
+
+  self.nargs = function (key, value) {
+    argsert('<string|object|array> [number]', [key, value], arguments.length)
+    populateParserHintObject(self.nargs, false, 'narg', key, value)
+    return self
+  }
+
+  self.choices = function (key, value) {
+    argsert('<object|string|array> [string|array]', [key, value], arguments.length)
+    populateParserHintObject(self.choices, true, 'choices', key, value)
+    return self
+  }
+
+  self.alias = function (key, value) {
+    argsert('<object|string|array> [string|array]', [key, value], arguments.length)
+    populateParserHintObject(self.alias, true, 'alias', key, value)
+    return self
+  }
+
+  // TODO: actually deprecate self.defaults.
+  self.default = self.defaults = function (key, value, defaultDescription) {
+    argsert('<object|string|array> [*] [string]', [key, value, defaultDescription], arguments.length)
+    if (defaultDescription) options.defaultDescription[key] = defaultDescription
+    if (typeof value === 'function') {
+      if (!options.defaultDescription[key]) options.defaultDescription[key] = usage.functionDescription(value)
+      value = value.call()
     }
+    populateParserHintObject(self.default, false, 'default', key, value)
+    return self
+  }
+
+  self.describe = function (key, desc) {
+    argsert('<object|string|array> [string]', [key, desc], arguments.length)
+    populateParserHintObject(self.describe, false, 'key', key, true)
+    usage.describe(key, desc)
+    return self
+  }
+
+  self.demandOption = function (keys, msg) {
+    argsert('<object|string|array> [string]', [keys, msg], arguments.length)
+    populateParserHintObject(self.demandOption, false, 'demandedOptions', keys, msg)
     return self
   }
 
-  self.normalize = function (strings) {
-    options.normalize.push.apply(options.normalize, [].concat(strings))
+  self.coerce = function (keys, value) {
+    argsert('<object|string|array> [function]', [keys, value], arguments.length)
+    populateParserHintObject(self.coerce, false, 'coerce', keys, value)
     return self
   }
 
+  function populateParserHintObject (builder, isArray, type, key, value) {
+    if (Array.isArray(key)) {
+      // an array of keys with one value ['x', 'y', 'z'], function parse () {}
+      var temp = {}
+      key.forEach(function (k) {
+        temp[k] = value
+      })
+      builder(temp)
+    } else if (typeof key === 'object') {
+      // an object of key value pairs: {'x': parse () {}, 'y': parse() {}}
+      Object.keys(key).forEach(function (k) {
+        builder(k, key[k])
+      })
+    } else {
+      // a single key value pair 'x', parse() {}
+      if (isArray) {
+        options[type][key] = (options[type][key] || []).concat(value)
+      } else {
+        options[type][key] = value
+      }
+    }
+  }
+
   self.config = function (key, msg, parseFn) {
-    // allow to pass a configuration object
+    argsert('[object|string] [string|function] [function]', [key, msg, parseFn], arguments.length)
+    // allow a config object to be provided directly.
     if (typeof key === 'object') {
+      key = applyExtends(key, cwd)
       options.configObjects = (options.configObjects || []).concat(key)
       return self
     }
 
-    // allow to provide a parsing function
+    // allow for a custom parsing function.
     if (typeof msg === 'function') {
       parseFn = msg
       msg = null
@@ -231,78 +320,31 @@ function Yargs (processArgs, cwd, parentRequire) {
     ;(Array.isArray(key) ? key : [key]).forEach(function (k) {
       options.config[k] = parseFn || true
     })
+
     return self
   }
 
   self.example = function (cmd, description) {
+    argsert('<string> [string]', [cmd, description], arguments.length)
     usage.example(cmd, description)
     return self
   }
 
   self.command = function (cmd, description, builder, handler) {
+    argsert('<string|array|object> [string|boolean] [function|object] [function]', [cmd, description, builder, handler], arguments.length)
     command.addHandler(cmd, description, builder, handler)
     return self
   }
 
   self.commandDir = function (dir, opts) {
+    argsert('<string> [object]', [dir, opts], arguments.length)
     const req = parentRequire || require
     command.addDirectory(dir, self.getContext(), req, require('get-caller-file')(), opts)
     return self
   }
 
-  self.string = function (strings) {
-    options.string.push.apply(options.string, [].concat(strings))
-    return self
-  }
-
-  // The 'defaults' alias is deprecated. It will be removed in the next major version.
-  self.default = self.defaults = function (key, value, defaultDescription) {
-    if (typeof key === 'object') {
-      Object.keys(key).forEach(function (k) {
-        self.default(k, key[k])
-      })
-    } else {
-      if (defaultDescription) options.defaultDescription[key] = defaultDescription
-      if (typeof value === 'function') {
-        if (!options.defaultDescription[key]) options.defaultDescription[key] = usage.functionDescription(value)
-        value = value.call()
-      }
-      options.default[key] = value
-    }
-    return self
-  }
-
-  self.alias = function (x, y) {
-    if (typeof x === 'object') {
-      Object.keys(x).forEach(function (key) {
-        self.alias(key, x[key])
-      })
-    } else {
-      options.alias[x] = (options.alias[x] || []).concat(y)
-    }
-    return self
-  }
-
-  self.coerce = function (key, fn) {
-    if (typeof key === 'object' && !Array.isArray(key)) {
-      Object.keys(key).forEach(function (k) {
-        self.coerce(k, key[k])
-      })
-    } else {
-      [].concat(key).forEach(function (k) {
-        options.coerce[k] = fn
-      })
-    }
-    return self
-  }
-
-  self.count = function (counts) {
-    options.count.push.apply(options.count, [].concat(counts))
-    return self
-  }
-
-  // deprecated: the demand API is too overloaded, and is being
-  // deprecated in favor of .demandCommand() .demandOption().
+  // TODO: deprecate self.demand in favor of
+  // .demandCommand() .demandOption().
   self.demand = self.required = self.require = function (keys, max, msg) {
     // you can optionally provide a 'max' key,
     // which will raise an exception if too many '_'
@@ -318,7 +360,7 @@ function Yargs (processArgs, cwd, parentRequire) {
     }
 
     if (typeof keys === 'number') {
-      self.demandCommand(keys, max, msg)
+      self.demandCommand(keys, max, msg, msg)
     } else if (Array.isArray(keys)) {
       keys.forEach(function (key) {
         self.demandOption(key, msg)
@@ -334,29 +376,18 @@ function Yargs (processArgs, cwd, parentRequire) {
     return self
   }
 
-  self.demandOption = function (key, msg) {
-    if (Array.isArray(key)) {
-      key.forEach(function (key) {
-        self.demandOption(key, msg)
-      })
-    } else {
-      if (typeof msg === 'string') {
-        options.demandedOptions[key] = { msg: msg }
-      // allow edge-case of options: {a: {demand: true}, b: {demand: false}}
-      } else if (msg === true || typeof msg === 'undefined') {
-        options.demandedOptions[key] = { msg: undefined }
-      }
-    }
+  self.demandCommand = function (min, max, minMsg, maxMsg) {
+    argsert('[number] [number|string] [string|null] [string|null]', [min, max, minMsg, maxMsg], arguments.length)
 
-    return self
-  }
+    if (typeof min === 'undefined') min = 1
 
-  self.demandCommand = function (min, max, minMsg, maxMsg) {
     if (typeof max !== 'number') {
       minMsg = max
       max = Infinity
     }
 
+    self.global('_', false)
+
     options.demandedCommands._ = {
       min: min,
       max: max,
@@ -368,34 +399,30 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.getDemandedOptions = function () {
+    argsert([], 0)
     return options.demandedOptions
   }
 
   self.getDemandedCommands = function () {
+    argsert([], 0)
     return options.demandedCommands
   }
 
-  self.requiresArg = function (requiresArgs) {
-    options.requiresArg.push.apply(options.requiresArg, [].concat(requiresArgs))
-    return self
-  }
-
-  self.skipValidation = function (skipValidations) {
-    options.skipValidation.push.apply(options.skipValidation, [].concat(skipValidations))
-    return self
-  }
-
   self.implies = function (key, value) {
+    argsert('<string|object> [string]', [key, value], arguments.length)
     validation.implies(key, value)
     return self
   }
 
   self.conflicts = function (key1, key2) {
+    argsert('<string|object> [string]', [key1, key2], arguments.length)
     validation.conflicts(key1, key2)
     return self
   }
 
   self.usage = function (msg, opts) {
+    argsert('<string|null|object> [object]', [msg, opts], arguments.length)
+
     if (!opts && typeof msg === 'object') {
       opts = msg
       msg = null
@@ -409,45 +436,49 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.epilogue = self.epilog = function (msg) {
+    argsert('<string>', [msg], arguments.length)
     usage.epilog(msg)
     return self
   }
 
   self.fail = function (f) {
+    argsert('<function>', [f], arguments.length)
     usage.failFn(f)
     return self
   }
 
-  self.check = function (f) {
-    validation.check(f)
+  self.check = function (f, _global) {
+    argsert('<function> [boolean]', [f, _global], arguments.length)
+    validation.check(f, _global !== false)
     return self
   }
 
-  self.describe = function (key, desc) {
-    if (typeof key === 'object') {
-      Object.keys(key).forEach(function (k) {
-        options.key[k] = true
+  self.global = function (globals, global) {
+    argsert('<string|array> [boolean]', [globals, global], arguments.length)
+    globals = [].concat(globals)
+    if (global !== false) {
+      options.local = options.local.filter(function (l) {
+        return globals.indexOf(l) === -1
       })
     } else {
-      options.key[key] = true
+      globals.forEach(function (g) {
+        if (options.local.indexOf(g) === -1) options.local.push(g)
+      })
     }
-    usage.describe(key, desc)
-    return self
-  }
-
-  self.global = function (globals) {
-    options.global.push.apply(options.global, [].concat(globals))
     return self
   }
 
   self.pkgConf = function (key, path) {
+    argsert('<string> [string]', [key, path], arguments.length)
     var conf = null
-
-    var obj = pkgUp(path)
+    // prefer cwd to require-main-filename in this method
+    // since we're looking for e.g. "nyc" config in nyc consumer
+    // rather than "yargs" config in nyc (where nyc is the main filename)
+    var obj = pkgUp(path || cwd)
 
     // If an object exists in the key, add it to options.configObjects
     if (obj[key] && typeof obj[key] === 'object') {
-      conf = obj[key]
+      conf = applyExtends(obj[key], path || cwd)
       options.configObjects = (options.configObjects || []).concat(conf)
     }
 
@@ -475,6 +506,8 @@ function Yargs (processArgs, cwd, parentRequire) {
   var parseFn = null
   var parseContext = null
   self.parse = function (args, shortCircuit, _parseFn) {
+    argsert('<string|array> [function|boolean|object] [function]', [args, shortCircuit, _parseFn], arguments.length)
+
     // a context object can optionally be provided, this allows
     // additional information to be passed to a command handler.
     if (typeof shortCircuit === 'object') {
@@ -496,18 +529,23 @@ function Yargs (processArgs, cwd, parentRequire) {
     freeze()
     if (parseFn) exitProcess = false
 
-    var parsed = parseArgs(args, shortCircuit)
+    var parsed = self._parseArgs(args, shortCircuit)
     if (parseFn) parseFn(exitError, parsed, output)
     unfreeze()
 
     return parsed
   }
 
+  self._getParseContext = function () {
+    return parseContext || {}
+  }
+
   self._hasParseCallback = function () {
     return !!parseFn
   }
 
   self.option = self.options = function (key, opt) {
+    argsert('<string|object> [object]', [key, opt], arguments.length)
     if (typeof key === 'object') {
       Object.keys(key).forEach(function (k) {
         self.options(k, key[k])
@@ -523,22 +561,31 @@ function Yargs (processArgs, cwd, parentRequire) {
 
       var demand = opt.demand || opt.required || opt.require
 
+      // deprecated, use 'demandOption' instead
       if (demand) {
         self.demand(key, demand)
       }
 
-      if ('demandOption' in opt) {
-        self.demandOption(key, opt.demandOption)
+      if (opt.demandOption) {
+        self.demandOption(key, typeof opt.demandOption === 'string' ? opt.demandOption : undefined)
       }
 
       if ('config' in opt) {
         self.config(key, opt.configParser)
       }
 
+      if ('conflicts' in opt) {
+        self.conflicts(key, opt.conflicts)
+      }
+
       if ('default' in opt) {
         self.default(key, opt.default)
       }
 
+      if ('implies' in opt) {
+        self.implies(key, opt.implies)
+      }
+
       if ('nargs' in opt) {
         self.nargs(key, opt.nargs)
       }
@@ -559,10 +606,6 @@ function Yargs (processArgs, cwd, parentRequire) {
         self.group(key, opt.group)
       }
 
-      if (opt.global) {
-        self.global(key)
-      }
-
       if (opt.boolean || opt.type === 'boolean') {
         self.boolean(key)
         if (opt.alias) self.boolean(opt.alias)
@@ -587,6 +630,10 @@ function Yargs (processArgs, cwd, parentRequire) {
         self.count(key)
       }
 
+      if (typeof opt.global === 'boolean') {
+        self.global(key, opt.global)
+      }
+
       if (opt.defaultDescription) {
         options.defaultDescription[key] = opt.defaultDescription
       }
@@ -612,10 +659,10 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.group = function (opts, groupName) {
+    argsert('<string|array> <string>', [opts, groupName], arguments.length)
     var existing = preservedGroups[groupName] || groups[groupName]
     if (preservedGroups[groupName]) {
-      // the preserved group will be moved to the set of explicitly declared
-      // groups
+      // we now only need to track this group name in groups.
       delete preservedGroups[groupName]
     }
 
@@ -634,19 +681,22 @@ function Yargs (processArgs, cwd, parentRequire) {
   // as long as options.envPrefix is not undefined,
   // parser will apply env vars matching prefix to argv
   self.env = function (prefix) {
+    argsert('[string|boolean]', [prefix], arguments.length)
     if (prefix === false) options.envPrefix = undefined
     else options.envPrefix = prefix || ''
     return self
   }
 
   self.wrap = function (cols) {
+    argsert('<number|null>', [cols], arguments.length)
     usage.wrap(cols)
     return self
   }
 
   var strict = false
-  self.strict = function () {
-    strict = true
+  self.strict = function (enabled) {
+    argsert('[boolean]', [enabled], arguments.length)
+    strict = enabled !== false
     return self
   }
   self.getStrict = function () {
@@ -654,13 +704,15 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.showHelp = function (level) {
-    if (!self.parsed) parseArgs(processArgs) // run parser, if it has not already been executed.
+    argsert('[string|function]', [level], arguments.length)
+    if (!self.parsed) self._parseArgs(processArgs) // run parser, if it has not already been executed.
     usage.showHelp(level)
     return self
   }
 
   var versionOpt = null
   self.version = function (opt, msg, ver) {
+    argsert('[string|function] [string|function] [string]', [opt, msg, ver], arguments.length)
     if (arguments.length === 0) {
       ver = guessVersion()
       opt = 'version'
@@ -669,6 +721,7 @@ function Yargs (processArgs, cwd, parentRequire) {
       opt = 'version'
     } else if (arguments.length === 2) {
       ver = msg
+      msg = null
     }
 
     versionOpt = opt
@@ -676,7 +729,6 @@ function Yargs (processArgs, cwd, parentRequire) {
 
     usage.version(ver || undefined)
     self.boolean(versionOpt)
-    self.global(versionOpt)
     self.describe(versionOpt, msg)
     return self
   }
@@ -690,6 +742,8 @@ function Yargs (processArgs, cwd, parentRequire) {
   var helpOpt = null
   var useHelpOptAsCommand = false // a call to .help() will enable this
   self.addHelpOpt = self.help = function (opt, msg, addImplicitCmd) {
+    argsert('[string|boolean] [string|boolean] [boolean]', [opt, msg, addImplicitCmd], arguments.length)
+
     // argument shuffle
     if (arguments.length === 0) {
       useHelpOptAsCommand = true
@@ -713,18 +767,19 @@ function Yargs (processArgs, cwd, parentRequire) {
     // use arguments, fallback to defaults for opt and msg
     helpOpt = opt || 'help'
     self.boolean(helpOpt)
-    self.global(helpOpt)
     self.describe(helpOpt, msg || usage.deferY18nLookup('Show help'))
     return self
   }
 
   self.showHelpOnFail = function (enabled, message) {
+    argsert('[boolean|string] [string]', [enabled, message], arguments.length)
     usage.showHelpOnFail(enabled, message)
     return self
   }
 
   var exitProcess = true
   self.exitProcess = function (enabled) {
+    argsert('[boolean]', [enabled], arguments.length)
     if (typeof enabled !== 'boolean') {
       enabled = true
     }
@@ -737,6 +792,8 @@ function Yargs (processArgs, cwd, parentRequire) {
 
   var completionCommand = null
   self.completion = function (cmd, desc, fn) {
+    argsert('[string] [string|boolean|function] [function]', [cmd, desc, fn], arguments.length)
+
     // a function to execute when generating
     // completions can be provided as the second
     // or third argument to completion.
@@ -759,16 +816,19 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.showCompletionScript = function ($0) {
+    argsert('[string]', [$0], arguments.length)
     $0 = $0 || self.$0
     _logger.log(completion.generateCompletionScript($0))
     return self
   }
 
   self.getCompletion = function (args, done) {
+    argsert('<array> <function>', [args, done], arguments.length)
     completion.getCompletion(args, done)
   }
 
   self.locale = function (locale) {
+    argsert('[string]', [locale], arguments.length)
     if (arguments.length === 0) {
       guessLocale()
       return y18n.getLocale()
@@ -779,6 +839,7 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.updateStrings = self.updateLocale = function (obj) {
+    argsert('<object>', [obj], arguments.length)
     detectLocale = false
     y18n.updateLocale(obj)
     return self
@@ -786,6 +847,7 @@ function Yargs (processArgs, cwd, parentRequire) {
 
   var detectLocale = true
   self.detectLocale = function (detect) {
+    argsert('<boolean>', [detect], arguments.length)
     detectLocale = detect
     return self
   }
@@ -807,14 +869,16 @@ function Yargs (processArgs, cwd, parentRequire) {
   // so that we can print to non-CLIs, e.g., chat-bots.
   var _logger = {
     log: function () {
-      var args = Array.prototype.slice.call(arguments)
+      const args = []
+      for (var i = 0; i < arguments.length; i++) args.push(arguments[i])
       if (!self._hasParseCallback()) console.log.apply(console, args)
       hasOutput = true
       if (output.length) output += '\n'
       output += args.join(' ')
     },
     error: function () {
-      var args = Array.prototype.slice.call(arguments)
+      const args = []
+      for (var i = 0; i < arguments.length; i++) args.push(arguments[i])
       if (!self._hasParseCallback()) console.error.apply(console, args)
       hasOutput = true
       if (output.length) output += '\n'
@@ -830,9 +894,14 @@ function Yargs (processArgs, cwd, parentRequire) {
     return hasOutput
   }
 
+  self._setHasOutput = function () {
+    hasOutput = true
+  }
+
   var recommendCommands
-  self.recommendCommands = function () {
-    recommendCommands = true
+  self.recommendCommands = function (recommend) {
+    argsert('[boolean]', [recommend], arguments.length)
+    recommendCommands = typeof recommend === 'boolean' ? recommend : true
     return self
   }
 
@@ -849,161 +918,182 @@ function Yargs (processArgs, cwd, parentRequire) {
   }
 
   self.terminalWidth = function () {
-    return process.stdout.columns
+    argsert([], 0)
+    return typeof process.stdout.columns !== 'undefined' ? process.stdout.columns : null
   }
 
   Object.defineProperty(self, 'argv', {
     get: function () {
-      var args = null
-
-      try {
-        args = parseArgs(processArgs)
-      } catch (err) {
-        usage.fail(err.message, err)
-      }
-
-      return args
+      return self._parseArgs(processArgs)
     },
     enumerable: true
   })
 
-  function parseArgs (args, shortCircuit) {
+  self._parseArgs = function (args, shortCircuit, _skipValidation, commandIndex) {
+    var skipValidation = !!_skipValidation
+    args = args || processArgs
+
     options.__ = y18n.__
     options.configuration = pkgUp()['yargs'] || {}
     const parsed = Parser.detailed(args, options)
     var argv = parsed.argv
-    if (parseContext) argv = assign(parseContext, argv)
+    if (parseContext) argv = assign(argv, parseContext)
     var aliases = parsed.aliases
 
     argv.$0 = self.$0
     self.parsed = parsed
 
-    guessLocale() // guess locale lazily, so that it can be turned off in chain.
+    try {
+      guessLocale() // guess locale lazily, so that it can be turned off in chain.
 
-    // while building up the argv object, there
-    // are two passes through the parser. If completion
-    // is being performed short-circuit on the first pass.
-    if (shortCircuit) {
-      return argv
-    }
+      // while building up the argv object, there
+      // are two passes through the parser. If completion
+      // is being performed short-circuit on the first pass.
+      if (shortCircuit) {
+        return argv
+      }
 
-    if (argv._.length) {
-      // check for helpOpt in argv._ before running commands
-      // assumes helpOpt must be valid if useHelpOptAsCommand is true
-      if (useHelpOptAsCommand) {
-        // 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 multiCharHelpCmds = helpCmds.filter(function (k) {
-          return k.length > 1
-        })
-        if (multiCharHelpCmds.length) helpCmds = multiCharHelpCmds
-        // look for and strip any helpCmds from argv._
-        argv._ = argv._.filter(function (cmd) {
-          if (~helpCmds.indexOf(cmd)) {
-            argv[helpOpt] = true
-            return false
+      if (argv._.length) {
+        // check for helpOpt in argv._ before running commands
+        // assumes helpOpt must be valid if useHelpOptAsCommand is true
+        if (useHelpOptAsCommand) {
+          // 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 multiCharHelpCmds = helpCmds.filter(function (k) {
+            return k.length > 1
+          })
+          if (multiCharHelpCmds.length) helpCmds = multiCharHelpCmds
+          // look for and strip any helpCmds from argv._
+          argv._ = argv._.filter(function (cmd) {
+            if (~helpCmds.indexOf(cmd)) {
+              argv[helpOpt] = true
+              return false
+            }
+            return true
+          })
+        }
+
+        // if there's a handler associated with a
+        // command defer processing to it.
+        var handlerKeys = command.getCommands()
+        if (handlerKeys.length) {
+          var firstUnknownCommand
+          for (var i = (commandIndex || 0), cmd; argv._[i] !== undefined; i++) {
+            cmd = String(argv._[i])
+            if (~handlerKeys.indexOf(cmd) && cmd !== completionCommand) {
+              setPlaceholderKeys(argv)
+              // commands are executed using a recursive algorithm that executes
+              // the deepest command first; we keep track of the position in the
+              // argv._ array that is currently being executed.
+              return command.runCommand(cmd, self, parsed, i + 1)
+            } else if (!firstUnknownCommand && cmd !== completionCommand) {
+              firstUnknownCommand = cmd
+              break
+            }
           }
-          return true
-        })
-      }
 
-      // if there's a handler associated with a
-      // command defer processing to it.
-      var handlerKeys = command.getCommands()
-      if (handlerKeys.length) {
-        var firstUnknownCommand
-        for (var i = 0, cmd; (cmd = argv._[i]) !== undefined; i++) {
-          if (~handlerKeys.indexOf(cmd) && cmd !== completionCommand) {
+          // run the default command, if defined
+          if (command.hasDefaultCommand() && !argv[helpOpt]) {
             setPlaceholderKeys(argv)
-            return command.runCommand(cmd, self, parsed)
-          } else if (!firstUnknownCommand && cmd !== completionCommand) {
-            firstUnknownCommand = cmd
+            return command.runCommand(null, self, parsed)
+          }
+
+          // recommend a command if recommendCommands() has
+          // been enabled, and no commands were found to execute
+          if (recommendCommands && firstUnknownCommand && !argv[helpOpt]) {
+            validation.recommendCommands(firstUnknownCommand, handlerKeys)
           }
         }
 
-        // recommend a command if recommendCommands() has
-        // been enabled, and no commands were found to execute
-        if (recommendCommands && firstUnknownCommand) {
-          validation.recommendCommands(firstUnknownCommand, handlerKeys)
+        // generate a completion script for adding to ~/.bashrc.
+        if (completionCommand && ~argv._.indexOf(completionCommand) && !argv[completion.completionKey]) {
+          if (exitProcess) setBlocking(true)
+          self.showCompletionScript()
+          self.exit(0)
         }
+      } else if (command.hasDefaultCommand() && !argv[helpOpt]) {
+        setPlaceholderKeys(argv)
+        return command.runCommand(null, self, parsed)
       }
 
-      // generate a completion script for adding to ~/.bashrc.
-      if (completionCommand && ~argv._.indexOf(completionCommand) && !argv[completion.completionKey]) {
+      // we must run completions first, a user might
+      // want to complete the --help or --version option.
+      if (completion.completionKey in argv) {
         if (exitProcess) setBlocking(true)
-        self.showCompletionScript()
-        self.exit(0)
-      }
-    }
 
-    // we must run completions first, a user might
-    // want to complete the --help or --version option.
-    if (completion.completionKey in argv) {
-      if (exitProcess) setBlocking(true)
-
-      // we allow for asynchronous completions,
-      // e.g., loading in a list of commands from an API.
-      var completionArgs = args.slice(args.indexOf('--' + completion.completionKey) + 1)
-      completion.getCompletion(completionArgs, function (completions) {
-        ;(completions || []).forEach(function (completion) {
-          _logger.log(completion)
-        })
-
-        self.exit(0)
-      })
-      return setPlaceholderKeys(argv)
-    }
-
-    var skipValidation = false
+        // we allow for asynchronous completions,
+        // e.g., loading in a list of commands from an API.
+        var completionArgs = args.slice(args.indexOf('--' + completion.completionKey) + 1)
+        completion.getCompletion(completionArgs, function (completions) {
+          ;(completions || []).forEach(function (completion) {
+            _logger.log(completion)
+          })
 
-    // Handle 'help' and 'version' options
-    Object.keys(argv).forEach(function (key) {
-      if (key === helpOpt && argv[key]) {
-        if (exitProcess) setBlocking(true)
+          self.exit(0)
+        })
+        return setPlaceholderKeys(argv)
+      }
 
-        skipValidation = true
-        self.showHelp('log')
-        self.exit(0)
-      } else if (key === versionOpt && argv[key]) {
-        if (exitProcess) setBlocking(true)
+      // Handle 'help' and 'version' options
+      // if we haven't already output help!
+      if (!hasOutput) {
+        Object.keys(argv).forEach(function (key) {
+          if (key === helpOpt && argv[key]) {
+            if (exitProcess) setBlocking(true)
+
+            skipValidation = true
+            self.showHelp('log')
+            self.exit(0)
+          } else if (key === versionOpt && argv[key]) {
+            if (exitProcess) setBlocking(true)
+
+            skipValidation = true
+            usage.showVersion()
+            self.exit(0)
+          }
+        })
+      }
 
-        skipValidation = true
-        usage.showVersion()
-        self.exit(0)
+      // Check if any of the options to skip validation were provided
+      if (!skipValidation && options.skipValidation.length > 0) {
+        skipValidation = Object.keys(argv).some(function (key) {
+          return options.skipValidation.indexOf(key) >= 0 && argv[key] === true
+        })
       }
-    })
 
-    // Check if any of the options to skip validation were provided
-    if (!skipValidation && options.skipValidation.length > 0) {
-      skipValidation = Object.keys(argv).some(function (key) {
-        return options.skipValidation.indexOf(key) >= 0 && argv[key] === true
-      })
-    }
+      // If the help or version options where used and exitProcess is false,
+      // or if explicitly skipped, we won't run validations.
+      if (!skipValidation) {
+        if (parsed.error) throw new YError(parsed.error.message)
 
-    // If the help or version options where used and exitProcess is false,
-    // or if explicitly skipped, we won't run validations
-    if (!skipValidation) {
-      if (parsed.error) throw parsed.error
-
-      // if we're executed via bash completion, don't
-      // bother with validation.
-      if (!argv[completion.completionKey]) {
-        validation.nonOptionCount(argv)
-        validation.missingArgumentValue(argv)
-        validation.requiredArguments(argv)
-        if (strict) validation.unknownArguments(argv, aliases)
-        validation.customChecks(argv, aliases)
-        validation.limitedChoices(argv)
-        validation.implications(argv)
-        validation.conflicting(argv)
+        // if we're executed via bash completion, don't
+        // bother with validation.
+        if (!argv[completion.completionKey]) {
+          self._runValidation(argv, aliases, {}, parsed.error)
+        }
       }
+    } catch (err) {
+      if (err instanceof YError) usage.fail(err.message, err)
+      else throw err
     }
 
     return setPlaceholderKeys(argv)
   }
 
+  self._runValidation = function (argv, aliases, positionalMap, parseErrors) {
+    if (parseErrors) throw new YError(parseErrors.message)
+    validation.nonOptionCount(argv)
+    validation.missingArgumentValue(argv)
+    validation.requiredArguments(argv)
+    if (strict) validation.unknownArguments(argv, aliases, positionalMap)
+    validation.customChecks(argv, aliases)
+    validation.limitedChoices(argv)
+    validation.implications(argv)
+    validation.conflicting(argv)
+  }
+
   function guessLocale () {
     if (!detectLocale) return