fix(language-service): use single entry point for Ivy and View Engine

Currently there are two entry points for the `@angular/language-service`
package:

- `@angular/language-service`
  This default entry point is for View Engine LS. Through the redirection
  of `main` field in `package.json`, it resolves to
  `./bundles/language-service.js`.
- `@angular/language-service/bundles/ivy.js`
  This secondary entry point is for Ivy LS.

TypeScript recently changed the behavior of tsserver to allow only package
names as plugin names [1] for security reasons. This means the secondary
entry point for Ivy LS can no longer be used.
We implemented a quick hack in the module resolver (in the extension repo)
to fix this, but the long term fix should be in `@angular/language-service`.

Here, the `main` field in `package.json` is changed to `index.js`, and in the
index file we conditionally load View Engine or Ivy based on the input config.
This eliminates the need for multiple entry points.

As part of this PR, I also removed all source code for View Engine and Ivy
included in the NPM package. Consumers of this package should run the bundled
output and nothing else. This would help us prevent an accidental import that
results in execution of unbundled code.

[1]: microsoft/TypeScript#42713

packages/language-service/BUILD.bazel

@@ -6,15 +6,17 @@ ts_library(
     name = "api",
     srcs = [
         "api.ts",
+        "index.ts",
     ],
     deps = [
+        "@npm//@types/node",
         "@npm//typescript",
     ],
 )
 
 ts_library(
     name = "language-service",
-    srcs = ["index.ts"] + glob(
+    srcs = glob(
         [
             "src/**/*.ts",
         ],
@@ -54,8 +56,7 @@ pkg_npm(
         "//integration:__pkg__",
     ],
     deps = [
-        ":language-service",
-        "//packages/language-service/ivy",
+        ":api",
         # min bundle is not used at the moment; omit from package to speed up build
         "//packages/language-service/bundles:language-service.js",
         "//packages/language-service/bundles:ivy.js",

packages/language-service/api.ts

@@ -14,6 +14,19 @@
 
 import * as ts from 'typescript';
 
+export interface NgLanguageServiceConfig {
+  /**
+   * If true, return only Angular results. Otherwise, return Angular + TypeScript
+   * results.
+   */
+  angularOnly: boolean;
+  /**
+   * If true, return factory function for Ivy LS during plugin initialization.
+   * Otherwise return factory function for View Engine LS.
+   */
+  ivy: boolean;
+}
+
 export type GetTcbResponse = {
   /**
    * The filename of the SourceFile this typecheck block belongs to.

packages/language-service/bundles/BUILD.bazel

@@ -3,7 +3,7 @@ load("//dev-infra/benchmark/ng_rollup_bundle:ng_rollup_bundle.bzl", "ng_rollup_b
 ng_rollup_bundle(
     name = "language-service",
     build_optimizer = False,
-    entry_point = "//packages/language-service:index.ts",
+    entry_point = "//packages/language-service:src/ts_plugin.ts",
     format = "amd",
     globals = {
         "fs": "fs",

packages/language-service/index.ts

@@ -6,5 +6,39 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import * as ts from 'typescript/lib/tsserverlibrary';
+import {NgLanguageService, NgLanguageServiceConfig} from './api';
+
 export * from './api';
-export {create, getExternalFiles} from './src/ts_plugin';
+
+interface PluginModule extends ts.server.PluginModule {
+  create(createInfo: ts.server.PluginCreateInfo): NgLanguageService;
+  onConfigurationChanged?(config: NgLanguageServiceConfig): void;
+}
+
+const factory: ts.server.PluginModuleFactory = function(mod): PluginModule {
+  let plugin: PluginModule;
+
+  function create(info: ts.server.PluginCreateInfo): NgLanguageService {
+    const config: NgLanguageServiceConfig = info.config;
+    const bundleName = config.ivy ? 'ivy.js' : 'language-service.js';
+    plugin = require(`./bundles/${bundleName}`)(mod);
+    return plugin.create(info);
+  }
+
+  function getExternalFiles(proj: ts.server.Project): string[] {
+    return plugin?.getExternalFiles?.(proj) ?? [];
+  }
+
+  function onConfigurationChanged(config: NgLanguageServiceConfig): void {
+    plugin?.onConfigurationChanged?.(config);
+  }
+
+  return {
+    create,
+    getExternalFiles,
+    onConfigurationChanged,
+  };
+};
+
+module.exports = factory;

packages/language-service/package.json

@@ -2,7 +2,7 @@
   "name": "@angular/language-service",
   "version": "0.0.0-PLACEHOLDER",
   "description": "Angular - language services",
-  "main": "./bundles/language-service.js",
+  "main": "./index.js",
   "typings": "./index.d.ts",
   "author": "angular",
   "license": "MIT",