docs: Add back script to generate example previews map (#60778)

Restores the ability to have example components rendered alongside the
code. This functionality was broken a while back by #53511.

To enable the embedded preview for an example, add `preview` and
`path=adev/src/content/expamples/component/to/render.ts` attributes to
the `<docs-code>` or `<docs-code-multifile>` tag.

Tested with one of the accessibility examples and it seems to work now.

PR Close #60778

adev/src/assets/previews/BUILD.bazel

@@ -1,15 +1,7 @@
-load("@build_bazel_rules_nodejs//:index.bzl", "copy_to_bin")
+load("//adev/shared-docs:index.bzl", "generate_previews")
 
-# TODO(josephperrott): Generate previews from source instead of using already generated files
-
-exports_files(
-    glob(["*"]),
-)
-
-copy_to_bin(
+generate_previews(
     name = "previews",
-    srcs = glob(["*"]),
-    visibility = [
-        "//visibility:public",
-    ],
+    example_srcs = "//adev/src/content/examples",
+    visibility = ["//visibility:public"],
 )

adev/src/assets/previews/previews.ts

@@ -1,21 +0,0 @@
-/*!
- * @license
- * Copyright Google LLC All Rights Reserved.
- *
- * Use of this source code is governed by an MIT-style license that can be
- * found in the LICENSE file at https://angular.dev/license
- */
-
-/**
- ******************************************************************************
- * DO NOT MANUALLY EDIT THIS FILE. THIS FILE IS AUTOMATICALLY GENERATED.
- ******************************************************************************
- */
-
-import {Type} from '@angular/core';
-
-/**
- * Map of the previews components, values are functions which returns the promise of the component type, which will be displayed as preview in the ExampleViewer component.
- * Keys has to be equal to paths written down in the docs markdown files.
- */
-export const PREVIEWS_COMPONENTS_MAP: Record<string, () => Promise<Type<unknown>>> = {};

adev/src/content/examples/BUILD.bazel

@@ -0,0 +1,7 @@
+filegroup(
+    name = "examples",
+    srcs = [
+        "//adev/src/content/examples/accessibility:ts_files",
+    ],
+    visibility = ["//visibility:public"],
+)

adev/src/content/examples/accessibility/BUILD.bazel

@@ -1,5 +1,26 @@
+load("//tools:defaults.bzl", "ng_module")
+
 package(default_visibility = ["//visibility:public"])
 
+filegroup(
+    name = "ts_files",
+    srcs = glob(["src/app/**/*.ts"]),
+    visibility = ["//visibility:public"],
+)
+
+ng_module(
+    name = "example",
+    srcs = [":ts_files"],
+    assets = glob([
+        "src/app/**/*.html",
+        "src/app/**/*.css",
+    ]),
+    visibility = ["//visibility:public"],
+    deps = [
+        "@npm//@angular/core",
+    ],
+)
+
 exports_files([
     "src/app/app.component.html",
     "src/app/app.component.ts",