ngc Task doesn't run when using ionic-app-scripts ngc

[bildonia]

Short description of the problem:

Running ionic-app-scripts ngc directly fails.
Output:

> ionic-app-scripts ngc

[10:25:21]  ionic-app-scripts 0.0.47
[10:25:21]  ngc started ...
[10:25:21]  ionic-app-script task: "ngc"
[10:25:21]  TypeError: Cannot read property 'fileCache' of undefined

What behavior are you expecting?

I expected to run ngc independent from the ionic-app-scripts build command. Here is output fro 0.0.45

> ionic-app-scripts ngc

[10:27:08]  ionic-app-scripts 0.0.45
[10:27:08]  ngc started ...
[10:27:20]  ngc finished in 11.93 s

Steps to reproduce:

1. Create a new project ionic start MyIonic2Project tutorial --v2
2. Update package.json devDependencies with "@ionic/app-scripts": "0.0.47"
3. Perform Upgrade steps for ionic-app-scripts 0.0.47
4. Update package.json with ngc command.
5. Run npm run ngc

package.json (scripts section)

"scripts": {
    "ionic:build": "ionic-app-scripts build",
    "ionic:serve": "ionic-app-scripts serve",
    "ngc": "ionic-app-scripts ngc"
  }

Which @ionic/app-scripts version are you using?
0.0.47

Other information:
I have tracked this down to node_modules/@ionic/app-scripts/dist/util/hybrid-file-system-factory.js:

"use strict";
var hybrid_file_system_1 = require('./hybrid-file-system');
var helpers_1 = require('./helpers');
var instance = null;
function getInstance() {
    if (!instance) {
        instance = new hybrid_file_system_1.HybridFileSystem(helpers_1.getContext().fileCache);
    }
    return instance;
}
exports.getInstance = getInstance;

helpers_1.getContext() is undefined at this point only when running ngc independent from ionic build

[danbucholtz]

Hi @bildonia,

This is out of scope at this time. If you want to run ngc directly, please use Angular's compiler-cli ngc binary. We use a custom ngc task that relies on other tasks, so it would be very difficult to get this to work in a stand-alone fashion.

Thanks,
Dan

[bildonia]

@danbucholtz Then why is this in the "All Available Tasks" section of the documentation?
https://github.com/driftyco/ionic-app-scripts

ngc | Runs just the ngc portion of the production build.

[danbucholtz]

I'll update the docs. Thanks for the heads up.

Thanks,
Dan