refactor(@angular-devkit/schematics): allow customization of node workflow engine host

This adds an option to the NodeWorkflow to allow a custom NodeModulesEngineHost to be used with the workflow.

Author: clydin

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

@@ -134,6 +134,7 @@ export declare class NodeWorkflow extends workflow.BaseWorkflow {
 
 export interface NodeWorkflowOptions {
     dryRun?: boolean;
+    engineHostCreator?: (options: NodeWorkflowOptions) => NodeModulesEngineHost;
     force?: boolean;
     optionTransforms?: OptionTransform<object, object>[];
     packageManager?: string;

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

@@ -25,6 +25,7 @@ export interface NodeWorkflowOptions {
   resolvePaths?: string[];
   schemaValidation?: boolean;
   optionTransforms?: OptionTransform<object, object>[];
+  engineHostCreator?: (options: NodeWorkflowOptions) => NodeModulesEngineHost;
 }
 
 /**
@@ -46,7 +47,8 @@ export class NodeWorkflow extends workflow.BaseWorkflow {
       root = options.root;
     }
 
-    const engineHost = new NodeModulesEngineHost(options.resolvePaths);
+    const engineHost =
+      options.engineHostCreator?.(options) || new NodeModulesEngineHost(options.resolvePaths);
     super({
       host,
       engineHost,