docs: fix the docs because the interface does not exist (#40308)

PR Close #40308

aio/content/examples/schematics-for-libraries/projects/my-lib/schematics/my-service/index.ts

@@ -6,37 +6,53 @@ import {
   chain, mergeWith
 } from '@angular-devkit/schematics';
 
-import { strings, normalize, experimental } from '@angular-devkit/core';
+import { strings, normalize, virtualFs, workspaces } from '@angular-devkit/core';
 // #enddocregion schematics-imports
 
 import { Schema as MyServiceSchema } from './schema';
 // #enddocregion schema-imports
 
-export function myService(options: MyServiceSchema): Rule {
-  return (tree: Tree) => {
-    const workspaceConfig = tree.read('/angular.json');
-    if (!workspaceConfig) {
-      throw new SchematicsException('Could not find Angular workspace configuration');
+function createHost(tree: Tree): workspaces.WorkspaceHost {
+  return {
+    async readFile(path: string): Promise<string> {
+      const data = tree.read(path);
+      if (!data) {
+        throw new SchematicsException('File not found.');
+      }
+      return virtualFs.fileBufferToString(data);
+    },
+    async writeFile(path: string, data: string): Promise<void> {
+      return tree.overwrite(path, data);
+    },
+    async isDirectory(path: string): Promise<boolean> {
+      return !tree.exists(path) && tree.getDir(path).subfiles.length > 0;
+    },
+    async isFile(path: string): Promise<boolean> {
+      return tree.exists(path);
+    },
+  };
 }
 
-    // convert workspace to string
-    const workspaceContent = workspaceConfig.toString();
+export function myService(options: MyServiceSchema): Rule {
+  return async (tree: Tree) => {
+    const host = createHost(tree);
+    const { workspace } = await workspaces.readWorkspace('/', host);
 
-    // parse workspace string into JSON object
-    const workspace: experimental.workspace.WorkspaceSchema = JSON.parse(workspaceContent);
 // #enddocregion workspace
+
+// #docregion project-info
 // #docregion project-fallback
     if (!options.project) {
-      options.project = workspace.defaultProject;
+      options.project = workspace.extensions.defaultProject;
     }
 // #enddocregion project-fallback
 
-// #docregion project-info
-    const projectName = options.project as string;
+    const project = workspace.projects.get(options.project);
+    if (!project) {
+      throw new SchematicsException(`Invalid project name: ${options.project}`);
+    }
 
-    const project = workspace.projects[projectName];
-
-    const projectType = project.projectType === 'application' ? 'app' : 'lib';
+    const projectType = project.extensions.projectType === 'application' ? 'app' : 'lib';
 // #enddocregion project-info
 
 // #docregion path

aio/content/guide/schematics-for-libraries.md

@@ -218,7 +218,8 @@ The `Tree` methods give you access to the complete file tree in your workspace,
 
 ### Get the project configuration
 
-1. To determine the destination project, use the `Tree.read()` method to read the contents of the workspace configuration file, `angular.json`, at the root of the workspace.
+1. To determine the destination project, use the `workspaces.readWorkspace` method to read the contents of the workspace configuration file, `angular.json`.
+   To use `workspaces.readWorkspace` you need to create a `workspaces.WorkspaceHost` from the `Tree`.
    Add the following code to your factory function.
 
 <code-example header="projects/my-lib/schematics/my-service/index.ts (Schema Import)" path="schematics-for-libraries/projects/my-lib/schematics/my-service/index.ts" region="workspace">
@@ -226,9 +227,7 @@ The `Tree` methods give you access to the complete file tree in your workspace,
 
   * Be sure to check that the context exists and throw the appropriate error.
 
-  * After reading the contents into a string, parse the configuration into a JSON object, typed to the `WorkspaceSchema`.
-
-1. The `WorkspaceSchema` contains all the properties of the workspace configuration, including a `defaultProject` value for determining which project to use if not provided.
+1. The `WorkspaceDefinition`, `extensions` property includes a `defaultProject` value for determining which project to use if not provided.
    We will use that value as a fallback, if no project is explicitly specified in the `ng generate` command.
 
 <code-example header="projects/my-lib/schematics/my-service/index.ts (Default Project)" path="schematics-for-libraries/projects/my-lib/schematics/my-service/index.ts" region="project-fallback">