Run parametrized task using grunt.task.run(taskname) - gruntjs

Question

I did stackoverflow search and looked at Grunt API docs but couldn't find a way to run a parametrized task using grunt.task.run(taskname).
I have a simple task which accepts a parameter and prints the message on console:
grunt.registerTask('hello', 'greeting task', function(name) {
if(!name || !name.length)
grunt.warn('you need to provide a name');
console.log('hello ' + name + '!');
});
I call the above task using below task which validates the task and if task exists then it runs it:
grunt.registerTask('validateandruntask', 'if task available then run given task', function(taskname) {
if(!taskname || !taskname.length) {
grunt.warn('task name is needed to run this task');
}
if(!grunt.task.exists(taskname)) {
grunt.log.writeln('this task does not exist!');
} else {
grunt.log.writeln(taskname + ' exists. Going to run this task');
grunt.task.run(taskname);
}
});
Now from command line, I am passing 'hello' task as parameter to 'validateandruntask' but I am not been able to pass the parameter to 'hello' task from command line:
This is what I tried on command line but it didn't work:
grunt validateandruntask:hello=foo
grunt validateandruntask:hello:param=name

Answer 1

First thing, the way to pass an arg through the command line is to use :.
For example to call hello directly:
grunt hello:you
To call it with multiple arguments, just separate them by :, like
grunt hello:mister:president
And to use these multiple arguments in the task, you do the same as plain Javascript: use arguments (all details here):
grunt.registerTask('hello', 'greeting task', function(name) {
if(!name || !name.length)
grunt.warn('you need to provide a name');
// unfortunately arguments is not an array,
// we need to convert it to use array methods like join()
var args = Array.prototype.slice.call(arguments);
var greet = 'hello ' + args.join(' ') + '!';
console.log(greet);
});
Then you want to call grunt validateandruntask:hello:mister:president, and modify your code to handle the variable parameters as well:
grunt.registerTask('validateandruntask', 'if task available then run given task', function(taskname) {
if(!taskname || !taskname.length) {
grunt.fail.fatal('task name is needed to run this task');
}
var taskToCall = taskname;
for(var i = 1; i < arguments.length; i++) {
taskToCall += ':' + arguments[i];
}
console.log(taskToCall);
if(!grunt.task.exists(taskname)) {
grunt.log.writeln('this task does not exist!');
} else {
grunt.log.writeln(taskname + ' exists. Going to run this task');
grunt.task.run(taskToCall);
}
});