Empty generators

[ozum]

Similar to #761, I need to run an empty generator. My use case is different though.

I'm developing an abstract generator. This base generator has a queued method called generateDbFiles, which is executed for each child generator. This method uses the _render() methods provided by the child generators.

this.queueMethod(async () => this.generateDbFiles(), `Database files generation`, "default");

So, child generators should provide a _render() method and some template files. If they don't want to change default behavior no more methods are necessary. This results in This Generator is empty. Add at least one method for it to run. error.

Could you please allow an empty generator? Otherwise, all child generators need to supply an empty stub method.

Many thanks,

[github-actions]

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[ozum]

Please reopen this issue.

[mshima]

@ozum can you want to provide a PR?
It should be optional.

[ozum]

@mshima

I would like to. Since I'm not familiar with the codebase, it seems enough to remove the condition below. Is it OK, or are there any dependent code?

generator/index.js line 935 contains:

    if (validMethods.length === 0 && this._prompts.length === 0) {
      throw new Error(
        'This Generator is empty. Add at least one method for it to run.'
      );
    }

[mshima]

I would like to. Since I'm not familiar with the codebase, it seems enough to remove the condition below. Is it OK, or are there any dependent code?

A generator without tasks is an error, unless you are doing advanced use like you said.
So it should be optional.
It's not just remove, you should add an option to features and if that option is set, don't throw that error.

[ozum]

Hmm,

Something like below?

    this.option('allow-empty-generator', {
      type: Boolean,
      description: 'Allows generators without tasks.',
      default: false
    });

// ...

    if (!this.options.allowEmptyGenerator && validMethods.length === 0 && this._prompts.length === 0) {
      throw new Error(
        'This Generator is empty. Add at least one method for it to run.'
      );
    }

[mshima]

The option should not be exposed to users, so no this.option(definition) is needed.
For yeoman-generator@5, I've added the features constructor parameter along with args and options.
args and options are passed by the final user, while features is for generator customizations.

So

   if (!this.features.allowEmptyGenerator && validMethods.length === 0 && this._prompts.length === 0) {
      throw new Error(
        'This Generator is empty. Add at least one method for it to run.'
      );
    }

And add tests.

[ozum]

Currently, I can't migrate to Yeoman 5. Is there a way for v4?

[mshima]

It's not worth, you can try to create a empty function on the object in the parent constructor:

this.notEmptyGenerator = function() {};

Object.assign(this, {function notEmptyGenerator()});

There are others alternatives if those don't work.

[ozum]

Thanks for the suggestion @mshima.