Grunt overriding task options

I am working on adding Grunt build system for an Angular/Cordova project. I am struggling to understand the behavior of inheritance / overriding of options for tasks.

I am working on configuring plugins grunt-contrib-jade and grunt-preprocessor but I am not not sure if I understand the business of overriding options correctly.

This is my whole Gruntfile.js for reference to ensure that I am not missing something.

'use strict';

module.exports = function(grunt) {
    require('load-grunt-tasks')(grunt);
    require("time-grunt")(grunt);

    grunt.initConfig({
        connect: {
            serve: {
                options: {
                    base: 'www/',
                    keepalive: true,
                    open: true
                }
            }
        },

        copy: {
            all: {
                expand: true,
                src: '**',
                dest: '../www/',
                cwd: 'app'
                //filter: 'isFile'
            }
        },

        compass: {
            options: {
                sassDir: 'app/style',
                cssDir: 'www/style',
            },

            dev: {
                debugInfo: true
            }
        },

        preprocess: {
            dev: {
                options: {
                    context: {
                        MODE: 'prod'
                    }
                },

                src: 'app/index.html',
                dest: 'www/index.html'
            }
        },

        jade: {
            dev: {
                options: {
                    src: 'app/**/*.jade',
                    dest: 'www/',
                    expand: true,
                    ext: '.html',
                    pretty: true
                }
            }
        },

        shell: {
            runAndroid: {
               command: 'cordova run android'
            },

            buildAndroid: {
                command: 'cordova build android'
            }
        }
    });

    grunt.registerTask('default', ['connect:serve']);
    grunt.registerTask('run-android', ['shell:runAndroid']);
    grunt.registerTask('build-android', ['shell:buildAndroid']);
};

Here are a few example of the plugin configurations and their behavior,

Case A

When run with grunt -vv jade following configuration prints no files[] and options[] and no output files are generated.

jade: {
    options: {
        src: 'app/**/*.jade',
        dest: 'www/',
        expand: true,
        ext: '.html',
        pretty: true
    }
}

Case B

When run grunt -vv jade:dev with following configuration, things work perfectly and output files are generated along with files[] and options[] array being printed on the console with appropriate values.

jade: {
    dev: {
        src: 'app/**/*.jade',
        dest: 'www/',
        expand: true,
        ext: '.html',
        pretty: true
    }
}

Case C

When run with gunt -vv jade:dev with following configuration, output files are not generated and files[] is empty but options[] is printed correctly on console.

jade: {
    dev: {
        options: {
            src: 'app/**/*.jade',
            dest: 'www/',
            expand: true,
            ext: '.html',
            pretty: true
        }
    }
} 

I am trying to do something like following where I will have default options set at the task level but can override / add a few options for a specific target.

jade: {
    options: {
        src: 'app/**/*.jade',
        dest: 'www/',
        expand: true,
        ext: '.html',
    },

    dev: {
        options: {
            pretty: true
        }
    }
}

Am I missing something?

Versions used,

• grunt - 0.4.5
• grunt-cli - 0.1.3
• grunt-contrib-jade - 0.12.0
• grunt-preprocessor - 4.0.0