Dynamic merge of JSON files in Gruntfile.js

In my gruntfile.js I'm using this plugin `grunt.loadNpmTasks('grunt-json-merge'); and I'm trying to merge two JSON files using this code:

    json_merge: {
        files: {
            files: { 'dest/resources/locales/merged.json':
                function () {
                    var includedScripts = [];
                                    includedScripts.push(project_x+'/locales/locale-fr.json');
                                    includedScripts.push(project_y+'/locales/locale-fr.json');
                    return includedScripts;

}
            },
        },
    }

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

NB: I need to use a function to define the input values as it contains some variables and maybe I will need to integrate a for loop later.

The used library is this one https://github.com/ramiel/grunt-json-merge

The problem is that the value of an entry in the files object should be an array, but because you haven't called the function, only declared it, the value is a function.

This should work:

json_merge: {
    files: {
        files: { 'dest/resources/locales/merged.json':
            (function () {
                var includedScripts = [];
                includedScripts.push(project_x+'/locales/locale-fr.json');
                includedScripts.push(project_y+'/locales/locale-fr.json');
                return includedScripts;
            })() // call the function here to return the array
        },
    }
}

But you might also find it more comfortable to extract the function, give it a name, and then invoke it by name in the task:

function getJSONFilesToMerge () {
    var includedScripts = [];
    includedScripts.push(project_x+'/locales/locale-fr.json');
    includedScripts.push(project_y+'/locales/locale-fr.json');
    return includedScripts;
}

// .....

json_merge: {
    files: {
        files: { 
            'dest/resources/locales/merged.json': getJSONFilesToMerge()
        },
    }
}