Add circular dependency plugin to Webpack config

[eppsilon]

Bug Report or Feature Request (mark with an x)

- [ ] bug report -> please search issues before submitting
- [X] feature request

Versions.

@angular/cli: 1.1.2
node: 6.11.0
os: darwin x64
@angular/animations: 4.2.3
@angular/common: 4.2.3
@angular/compiler: 4.2.3
@angular/core: 4.2.3
@angular/forms: 4.2.3
@angular/http: 4.2.3
@angular/platform-browser: 4.2.3
@angular/platform-browser-dynamic: 4.2.3
@angular/platform-server: 4.2.3
@angular/router: 4.2.3
@angular/cli: 1.1.2
@angular/compiler-cli: 4.2.3
@angular/language-service: 4.2.3

Desired functionality.

Circular dependency bugs are easy to introduce and can be hard to detect and troubleshoot. Sometimes everything works fine, but in a few cases I've had module imports show up as undefined at runtime. Last time it happened, it was only in AOT mode, so I didn't catch it initially.

It would be helpful if the CLI included a plugin that warns you if circular dependencies are detected and logs the modules that are part of the cycle.

Mention any other details that might be useful.

I used this plugin and it found several issues in my project.

However, I couldn't configure Webpack to use the plugin without ejecting the config, and I'd rather not have to do that each time I need to debug an issue like this.

[filipesilva]

I'll have a look. I agree it's a difficult to debug issue and that we should add a plugin if it helps and has no unexpected side effects.