Overeager files interpretation in multi-tasks

[RolKau]

If a multi-task is registered, and this multi-task is invoked with a section which is an array while grunt is run with the --verbose
option, the build will terminate with the error message:

Warning: pattern.indexOf is not a function Use --force to continue.

The exception itself is thrown at line 45 in file.js, but it comes from task.normalizeMultiTaskFiles at line 168 in task.js
where src is now [1, 2, 3] when it processes the foo section, because line 110 in task.js interprets the foo section as if it was a file specification in a non-multi-task, and creates an object with src=[1, 2, 3] and dest='foo'.

Consider the example from the documentation:

module.exports = grunt => {
  grunt.initConfig({
    log: {
      foo: [1, 2, 3],
      bar: 'hello world',
      baz: false
    }
  });

  grunt.task.registerMultiTask('log', 'Log stuff.', function() {
    grunt.log.writeln(this.target + ': ' + this.data);
  });
}

Given now also a package.json of:

{
  "main": "index.js",
  "scripts": {
    "build": "grunt log",
    "verbose": "grunt log --verbose"
  },
  "devDependencies": {
    "grunt": "1.6.1"
  }
}

one can reproduce the error with:

npm i
npm run build
npm run verbose