fix(@angular/cli): inform user and error if schematics package is in unreachable location (#16466)

This is a workaround for the schematics runtime to support the requirement of packages containing migrations (or other schematics) to not have a direct/runtime dependency on the schematics package.

Closes: #16392

Author: alan-agius4

packages/angular/cli/commands/add-impl.ts

@@ -18,7 +18,6 @@ import { colors } from '../utilities/color';
 import { getPackageManager } from '../utilities/package-manager';
 import {
   NgAddSaveDepedency,
-  PackageIdentifier,
   PackageManifest,
   fetchPackageManifest,
   fetchPackageMetadata,
@@ -29,7 +28,6 @@ const npa = require('npm-package-arg');
 
 export class AddCommand extends SchematicCommand<AddCommandSchema> {
   readonly allowPrivateSchematics = true;
-  readonly allowAdditionalArgs = true;
 
   async run(options: AddCommandSchema & Arguments) {
     if (!options.collection) {

packages/angular/cli/models/schematic-command.ts

@@ -73,7 +73,6 @@ export abstract class SchematicCommand<
   T extends BaseSchematicSchema & BaseCommandOptions
 > extends Command<T> {
   readonly allowPrivateSchematics: boolean = false;
-  readonly allowAdditionalArgs: boolean = false;
   private _host = new NodeJsSyncHost();
   private _workspace: workspaces.WorkspaceDefinition;
   protected _workflow: NodeWorkflow;
@@ -466,8 +465,10 @@ export abstract class SchematicCommand<
       args = await this.parseArguments(schematicOptions || [], o);
     }
 
-    // ng-add is special because we don't know all possible options at this point
-    if (args['--'] && !this.allowAdditionalArgs) {
+    const allowAdditionalProperties =
+      typeof schematic.description.schemaJson === 'object' && schematic.description.schemaJson.additionalProperties;
+
+    if (args['--'] && !allowAdditionalProperties) {
       args['--'].forEach(additional => {
         this.logger.fatal(`Unknown option: '${additional.split(/=/)[0]}'`);
       });

tests/legacy-cli/e2e/tests/commands/add/add-material.ts

@@ -6,7 +6,15 @@ export default async function () {
   // forcibly remove in case another test doesn't clean itself up
   await rimraf('node_modules/@angular/material');
 
-  await ng('add', '@angular/material');
+  try {
+    await ng('add', '@angular/material', '--unknown');
+  } catch (error) {
+    if (!(error.message && error.message.includes(`Unknown option: '--unknown'`))) {
+      throw error;
+    }
+  }
+
+  await ng('add', '@angular/material', '--theme', 'custom', '--verbose');
   await expectFileToMatch('package.json', /@angular\/material/);
 
   const output1 = await ng('add', '@angular/material');