fix: the positional argument parse was clobbering global flag argumen…

…ts (#984)

lib/command.js

@@ -293,13 +293,26 @@ module.exports = function command (yargs, usage, validation) {
         return `--${key} ${value}`
       }))
     })
+
+    // short-circuit parse.
+    if (!unparsed.length) return
+
     const parsed = Parser.detailed(unparsed.join(' '), options)
 
     if (parsed.error) {
       yargs.getUsageInstance().fail(parsed.error.message, parsed.error)
     } else {
+      // only copy over positional keys (don't overwrite
+      // flag arguments that were already parsed).
+      const positionalKeys = Object.keys(positionalMap)
+      Object.keys(positionalMap).forEach((key) => {
+        [].push.apply(positionalKeys, parsed.aliases[key])
+      })
+
       Object.keys(parsed.argv).forEach((key) => {
-        if (key !== '_') argv[key] = parsed.argv[key]
+        if (positionalKeys.indexOf(key) !== -1) {
+          argv[key] = parsed.argv[key]
+        }
       })
     }
   }

test/command.js

@@ -102,6 +102,15 @@ describe('Command', () => {
       expect(handlers.wat).to.not.exist
       command.getCommands().should.deep.equal(['foo', 'wat'])
     })
+
+    it('does not overwrite existing values in argv for keys that are not positional', () => {
+      const argv = yargs('foo foo.js --reporter=html')
+        .command('foo <file>')
+        .default('reporter', 'text')
+        .argv
+      argv.file.should.equal('foo.js')
+      argv.reporter.should.equal('html')
+    })
   })
 
   describe('variadic', () => {