fix(@schematics/angular): migrate style preprocessor options

Fixes: #10473

Author: clydin

packages/schematics/angular/migrations/update-6/index.ts

@@ -366,6 +366,16 @@ function extractProjectsConfig(config: CliConfig, tree: Tree): JsonObject {
         buildOptions.polyfills = appRoot + '/' + app.polyfills;
       }
 
+      if (app.stylePreprocessorOptions
+          && app.stylePreprocessorOptions.includePaths
+          && Array.isArray(app.stylePreprocessorOptions.includePaths)
+          && app.stylePreprocessorOptions.includePaths.length > 0) {
+        buildOptions.stylePreprocessorOptions = {
+          includePaths: app.stylePreprocessorOptions.includePaths
+            .map(includePath => join(app.root as Path, includePath)),
+        };
+      }
+
       buildOptions.assets = (app.assets || []).map(_mapAssets);
       buildOptions.styles = (app.styles || []).map(_extraEntryMapper);
       buildOptions.scripts = (app.scripts || []).map(_extraEntryMapper);

packages/schematics/angular/migrations/update-6/index_spec.ts

@@ -50,6 +50,11 @@ describe('Migration to v6', () => {
           styles: [
             'styles.css',
           ],
+          stylePreprocessorOptions: {
+            includePaths: [
+              'styleInc',
+            ],
+          },
           scripts: [],
           environmentSource: 'environments/environment.ts',
           environments: {
@@ -506,6 +511,7 @@ describe('Migration to v6', () => {
         expect(build.builder).toEqual('@angular-devkit/build-angular:browser');
         expect(build.options.scripts).toEqual([]);
         expect(build.options.styles).toEqual(['src/styles.css']);
+        expect(build.options.stylePreprocessorOptions).toEqual({includePaths: ['src/styleInc']});
         expect(build.options.assets).toEqual([
           { glob: '**/*', input: 'src/assets', output: '/assets' },
           { glob: 'favicon.ico', input: 'src', output: '/' },