How to fix: Angular / Ionic v4 "Can't find stylesheet to import" from library in monorepo project

Question

I have a monorepo project that includes a library, several projects, and the main project. My ionic project is in the projects folder.

I cannot build my ionic project (ionic build or ng build) because it imports a module from the main project (src/) which imports a sass file from a third project in the libs/ folder.

When building with ionic build, I get the error:

"Can't find stylesheet to import."

@import 'libs/...';

When I build with the ng-cli, I get errors for each of the references to sass files imported from libs/... seemingly everywhere in the project, even files/modules that aren't imported in this project.

I don't have any issue building other projects that import from the folder.

The package.json file inside of the ionic project folder includes this snippet:

"config": {
    "ionic_webpack": "./webpack.config.js",
    "ionic_sass": "./sass.config.js",
    "ionic_source_map_type": "source-map"
  },

My custom config is pasted below, I've tried variations of including ../../ or not and running ionic build from both the root directory and the project root:

const useDefaultConfig = require('@ionic/app-scripts/config/sass.config.js');

useDefaultConfig.includePaths.push('libs/path/to/assets/scss');
useDefaultConfig.includePaths.push('libs/path/to/assets/scss/partials');
useDefaultConfig.includePaths.push('../../libs/path/to/assets/scss');
useDefaultConfig.includePaths.push('../../libs/path/to/assets/scss/partials');

useDefaultConfig.includePaths.push('dist/path/to/assets/scss');
useDefaultConfig.includePaths.push('dist/path/to/assets/scss/partials');
useDefaultConfig.includePaths.push('../../dist/path/to/assets/scss');
useDefaultConfig.includePaths.push('../../dist/path/to/assets/scss/partials');

module.exports = useDefaultConfig;

I also tried doing

module.exports = function(){ return useDefualtConfig; };

I added paths to the stylePreprocessorOptions.includePaths in the project's section of the angular.json file like so:

"stylePreprocessorOptions": {
    "includePaths": [
        "libs/path",
        "libs/path/assets/scss",
        "libs/path/assets/scss/partials",
        "dist/path",
        "dist/path/assets/scss",
        "dist/path/assets/scss/partials"
    ]
},

I also included the paths in both tsconfig.app.json and tsconfig.json.