args parser cannot accept option arguments starting with a hyphen

[DartBot]

This issue was originally filed by @hoylen

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What steps will reproduce the problem?

1. Run the program below with arguments "-t -32"

dart bin/test-args-hyphen.dart -t -32

What is the expected output? What do you see instead?

Expected: Temperature is: -32

Got: FormatException: Missing argument for "temperature".

It treats the option argument as another option instead of the argument to the "-t" option.

What version of the product are you using?

1.8.3

On what operating system?

linux_x64

Please provide any additional information below.

// Test program

import 'package:args/args.dart';

void main(List<String> arguments) {

  var parser = new ArgParser(allowTrailingOptions: true);
  parser.addOption('temperature', abbr: 't', help: 'degrees');

  var results = parser.parse(arguments);

  print("Temperature is: ${results['temperature']}");;
}

//EOF

[lrhn]

Added Pkg-Args, Area-Pkg, Triaged labels.

[DartBot]

This issue has been moved to dart-lang/args#36.