Grunt - resolving non-string (eg array) templates

Question

Say I have a variable in my grunt config with an array as a value. A real world example is grunt.regarde.changed from the grunt-regarde plugin, which lists all

Answer 1

// assuming that regarde is a grunt plugin (haven't used—link is broken)

copy: {
  staticWeb: {
    src: '<% regarde.changed %>',
    dest: 'someDir'
  }
}

http://gruntjs.com/api/grunt.config#grunt.config.getraw

#ezpz

Answer 2

Have you tried:

copy: {
  staticWeb: {
    src: '<%= grunt.regarde.changed.split(",") %>',
    dest: 'someDir'
  }
}

Answer 3

I had exactly the same problem as yours, solve it by surrounding your template with curly brackets.

So here is your code, modified

copy: {
  staticWeb: {
    src: '{<%= grunt.regarde.changed %>}', // added curly brackets
    dest: 'someDir'
  }
}

It will output the src as {source1,source2,source3}, which is the same as using an array. (See Globbing Patterns in Grunt Documentation)

Answer 4

The problem is very easy to fix once you know how, just a few lines of code, but it took me quite a while to dig up all the relevant info from the Grunt source code in order to understand what to do, so bear with me while I take you through the background ...

---

The general way of getting hold of a property on the configuration object is straight forward:

<%= some.property %> // fetches grunt.config.get('some.property')

That works for all properties that have been set on the grunt.config object, which (of course) include the config that is passed into grunt.initConfig(). This is why you can reference other tasks variables directly, such as in <%= concat.typescriptfiles.dest %>, as all the properties in the config object is in the template's own scope.

Technically this expansion happens when the (LoDash) template is passed along with either the options object (if defined) or the grunt.config object to the template processor (LoDash' template function).

So this works for values that have been set in the config itself, or by using dynamically assigned values through grunt.config.set(). See the API docs for more info.

What does not work in the same way is accessing values that are not availabe on the configuration object. It seems that for some reason I am not quite sure of, all other values always ends up as strings. This happens regardless of whether you access them directly or through method calls. For instance trying to get access to an array on the config through grunt.config.get() gets you a string.

A workaround for the problem that preserves file order

The accepted answer works in a way, but due to the globbing syntax it will be parsed by the glob() module which does not preserve file order. This was a no-no for my build.

A workaround, in case the array you want to use is not available on the config object, is to add it to the config via an intermediary task. Something like the following should work:

// This variable will be used twice to demonstrate the difference
// between directly setting an attribute on the grunt object
// and using the setter method on the grunt.config object
var myFiles = ['c/file1.txt', 'a/file2.txt', 'b/file3.txt']
module.exports = function(grunt){

    grunt.initConfig({

        debug : {
            using_attribute: {
                src : '<%= grunt.value_as_attribute %>' // will be a string
            },
            using_task: {
                src : '<%= value_by_setter %>' // will be an array
            },
            no_task_direct_setter: {
                src : '<%= value_by_setter_early %>' // will be an array
            }
        }        
    });

    grunt.registerTask('myValSetter', function() {
        grunt.config.set('value_by_setter', myFiles );
    });

    // a task that will report information on our set values
    grunt.registerMultiTask('debug', function(){
        grunt.log.writeln('data.src: ', this.data.src);
        grunt.log.writeln('type: ', Array.isArray(this.data.src)? "Array" : typeof this.data.src);
    });

    grunt.value_as_attribute = myFiles;

    grunt.config.set('value_by_setter_early', myFiles );

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

This will output

$ grunt
Running "myValSetter" task

Running "debug:using_attribute" (debug) task
data.src:  c/file1.txt,a/file2.txt,b/file3.txt
type:  string

Running "debug:using_task" (debug) task
data.src:  [ 'c/file1.txt', 'a/file2.txt', 'b/file3.txt' ]
type:  Array

Running "debug:no_task_direct_setter" (debug) task
data.src:  [ 'c/file1.txt', 'a/file2.txt', 'b/file3.txt' ]
type:  Array

Done, without errors.

This example is just meant to illustrate the concept, but you should be able to easily customize it to your instance :)