grunt-babel example from readme generates exception

[breeeew]

'use strict';

module.exports = function(grunt) {

require('load-grunt-tasks')(grunt); // npm install --save-dev load-grunt-tasks

grunt.initConfig({
    babel: {
        options: {
            sourceMap: true
        },
        dist: {
            files: {
                'dist/app.js': 'src/app.js'
            }
        }
    }
});

grunt.registerTask('default', ['babel']);
};

generates exception:

grunt
Running "babel:dist" (babel) task
Warning: path must be a string Use --force to continue.

Aborted due to warnings.

[anthonybrown]

I'm getting the same error, how did you solve this?

[agdm]

same here.

[breeeew]

I wrote incorrectly "files" section. My sources placed in "src_babel/", and i build it to "build/", and i wrote:

dist: {
  files: {
    'src_babel/**/*.js': 'build/'
  }
}

My fixed and full Grunfile:

'use strict';

module.exports = function(grunt) {
  grunt.initConfig({
    clean: ['build/', 'test_build/'],
    jasmine_node: {
        options: {
            forceExit: true,
            match: '.',
            matchall: false,
            extensions: 'js',
            specNameMatcher: ''
        },
        all: ['test_build/']
    },
    coffee: {
        compile: {
            options: {
                bare: true
            },
            expand: true,
            cwd: 'src',
            src: ['**/*.coffee'],
            dest: 'build/',
            ext: '.js'
        },
        compileTests:
        {
            cwd: 'test',
            expand: true,
            src: ['**/*.coffee'],
            dest: 'test_build/',
            ext: '.js'
        }
    },
    coffeelint: {
        app: ['src/**/*.coffee', '!src/test/**/*.coffee', '!src/node_modules/**'],
        options: {
            'max_line_length' : {
                'level': 'ignore'
            }
        }
    },
    babel: {
      options: {
        sourceMap: true,
        stage: 0,
        optional: ['runtime']
      },
      dist: {
        files: [{
          expand: true,     // Enable dynamic expansion.
          cwd: 'src_babel/',      // Src matches are relative to this path.
          src: ['**/*.js'],
          dest: 'build/',   // Destination path prefix.
          ext: '.js',   // Dest filepaths will have this extension.
          extDot: 'first'   // Extensions in filenames begin after the first dot
        }]
      },
      test: {
        options: {
          sourceMap: false
        },
        files:[{
          expand: true,     // Enable dynamic expansion.
          cwd: 'test_babel/',      // Src matches are relative to this path.
          src: ['**/*.js'],
          dest: 'test_build/',   // Destination path prefix.
          ext: '.js',   // Dest filepaths will have this extension.
          extDot: 'first'   // Extensions in filenames begin after the first dot
        }]
      }
    }
});

    grunt.loadNpmTasks('grunt-contrib-coffee');
    grunt.loadNpmTasks('grunt-contrib-clean');
    grunt.loadNpmTasks('grunt-coffeelint');
    grunt.loadNpmTasks('grunt-jasmine-node');
    grunt.loadNpmTasks('grunt-babel');

    // Default task.
    grunt.registerTask('default', ['clean', 'coffee', 'babel', 'jasmine_node']);

    grunt.registerTask('lint', ['coffeelint']);
    grunt.registerTask('test', ['jasmine_node']);
};

[tandrewnichols]

This error actually happens anytime the src files are empty, which feels like a problem. If we want to migrate our existing infrastructure from using es5 to es6, we might want to specify the files that grunt-babel should compile as some/directory/**/*.es6 and then we can make changes as we go. But this fails until at least one *.es6 file exists.