refactor(@angular-devkit/schematics): allow direct workflow option transforms

This change allows option transforms to be directly provided to the NodeWorkflow instead of needing to access the engine host inside the workflow after creation.  This also allows option transforms to affect the options prior to schema validation (if enabled).

Author: clydin

etc/api/angular_devkit/schematics/tools/index.d.ts

@@ -135,6 +135,7 @@ export declare class NodeWorkflow extends workflow.BaseWorkflow {
 export interface NodeWorkflowOptions {
     dryRun?: boolean;
     force?: boolean;
+    optionTransforms?: OptionTransform<object, object>[];
     packageManager?: string;
     packageRegistry?: string;
     registry?: schema.CoreSchemaRegistry;

packages/angular_devkit/schematics/tools/workflow/node-workflow.ts

@@ -12,6 +12,7 @@ import {
 } from '@angular-devkit/schematics';  // tslint:disable-line:no-implicit-dependencies
 import { BuiltinTaskExecutor } from '../../tasks/node';
 import { FileSystemEngine } from '../description';
+import { OptionTransform } from '../file-system-engine-host-base';
 import { NodeModulesEngineHost } from '../node-module-engine-host';
 import { validateOptionsWithSchema } from '../schema-option-transform';
 
@@ -23,6 +24,7 @@ export interface NodeWorkflowOptions {
   registry?: schema.CoreSchemaRegistry;
   resolvePaths?: string[];
   schemaValidation?: boolean;
+  optionTransforms?: OptionTransform<object, object>[];
 }
 
 /**
@@ -66,6 +68,12 @@ export class NodeWorkflow extends workflow.BaseWorkflow {
     engineHost.registerTaskExecutor(BuiltinTaskExecutor.RunSchematic);
     engineHost.registerTaskExecutor(BuiltinTaskExecutor.TslintFix);
 
+    if (options.optionTransforms) {
+      for (const transform of options.optionTransforms) {
+        engineHost.registerOptionsTransform(transform);
+      }
+    }
+
     if (options.schemaValidation) {
       engineHost.registerOptionsTransform(validateOptionsWithSchema(this.registry));
     }