The installation of preset throws an error "Failed to resolve plugin" when plugin doesn't have generator

[vatson]

Version

3.0.0-rc.5

Reproduction link

https://github.com/vatson/vue-cli-plugin-ts-paths/tree/759ed44c4499f37429556ee2e3c33b66d4278c3f

Steps to reproduce

1. Create a plugin without generator
2. Create a preset that uses the plugin without generator
3. Try to install just created preset

What is expected?

Installation is successful.

What is actually happening?

Error: Failed to resolve plugin:

---

The error is thrown from https://github.com/vuejs/vue-cli/blob/dev/packages/%40vue/cli/lib/Creator.js#L312

I didn't dig deep but for some reasons the error isn't thrown when you try to install from local preset.

[vatson]

We do not always need plugins that generate something. It can be a plugin that just tunes your webpack config or adds a useful command