fix: check aliases when guessing defaults for arguments fixes #41 (#43)

index.js

@@ -594,9 +594,9 @@ function parse (args, opts) {
   function guessType (key, flags) {
     var type = 'boolean'
 
-    if (flags.strings && flags.strings[key]) type = 'string'
-    else if (flags.numbers && flags.numbers[key]) type = 'number'
-    else if (flags.arrays && flags.arrays[key]) type = 'array'
+    if (checkAllAliases(key, flags.strings)) type = 'string'
+    else if (checkAllAliases(key, flags.numbers)) type = 'number'
+    else if (checkAllAliases(key, flags.arrays)) type = 'array'
 
     return type
   }

test/yargs-parser.js

@@ -1903,4 +1903,34 @@ describe('yargs-parser', function () {
       })
     })
   })
+
+  // addresses: https://github.com/yargs/yargs-parser/issues/41
+  it('defaults to empty array if array option is provided no values', function () {
+    var parsed = parser(['-f'], {
+      'alias': {
+        'f': 'files'
+      },
+      'array': ['files']
+    })
+    parsed.f.should.deep.equal([])
+    parsed.files.should.deep.equal([])
+
+    parsed = parser(['--files'], {
+      'alias': {
+        'f': 'files'
+      },
+      'array': ['files']
+    })
+    parsed.f.should.deep.equal([])
+    parsed.files.should.deep.equal([])
+
+    parsed = parser(['-f', '-y'], {
+      'alias': {
+        'f': 'files'
+      },
+      'array': ['files']
+    })
+    parsed.f.should.deep.equal([])
+    parsed.files.should.deep.equal([])
+  })
 })