How to gracefully abort yeoman generator on error? - yeoman

Question

I'm writing a yeoman generator and want to check some prerequisites, for example a git being installed. I can easily check this using .exec, but how do i gracefully abort generator and report error to user? I searched docs, but it seems that i'm missing some obvious way to do it. Any hints?
Throwing exception will of course abort generator, but is it a best way? Maybe something more user friendly? Not all yeoman users are able to read js exceptions.

Answer 1

The current state of error handling in the popular generators is quite diverse:
in the most cases they just log the error and return from the action and let the subsequnt actions run and return 0 status code:
generator-karma's setupTravis method:
if (err) {
this.log.error('Could not open package.json for reading.', err);
done();
return;
}
or set a custom abort property on error and skip further actions with cheking on the abort property but still return 0 status code:
generator-jhipster's CloudFoundryGenerator:
CloudFoundryGenerator.prototype.checkInstallation = function checkInstallation() {
if(this.abort) return;
var done = this.async();
exec('cf --version', function (err) {
if (err) {
this.log.error('cloudfoundry\'s cf command line interface is not available. ' +
'You can install it via https://github.com/cloudfoundry/cli/releases');
this.abort = true;
}
done();
}.bind(this));
};
or manually end the process with process.exit:
generator-mobile's configuringmethod:
if (err) {
self.log.error(err);
process.exit(1);
}
However none of these methods provide a good way to signal to the environment that something went wrong except the last one but directly calling process.exit is a design smell.
Throwing an exception is also an option but this presents also the stackstrace to the user which is not always a good idea.
The best option would be use the Environment.error method, which has some nice advantages:
the Environment is exposed thorough the env property of the yeoman.generators.Base
an error event is emitted which is handled by the yo cli code
the execution will result in a non zero (error) status code which is override-able
by default yo will display only the message and no stacktrace
the stacktrace can be optionally displayed with providing the --debug built-in option when re-running the generator.
With using this technique your action method would look like this:
module.exports = generators.Base.extend({
method1: function () {
console.log('method 1 just ran');
this.env.error("something bad is happened");
console.log('this won't be executed');
},
method2: function () {
console.log('this won't be executed');
}
});