refactor(cdk/schematics): use schematics addDependency helper in cdk ng-add

The `addDependency` helper from `@schematics/angular/utility` reduces the
amount of custom code to conditionally add the `@angular/cdk` dependency
within the package's `ng add` schematic. This also allows remove of some
of the additional helper code within the schematic. Unfortunately, not all
can be removed as some is used within the unit tests for the schematic.

Author: clydin

src/cdk/schematics/ng-add/index.spec.ts

@@ -2,12 +2,48 @@ import {Tree} from '@angular-devkit/schematics';
 import {SchematicTestRunner} from '@angular-devkit/schematics/testing';
 import {COLLECTION_PATH} from '../paths';
 import {createTestApp, getFileContent} from '../testing';
-import {addPackageToPackageJson} from './package-config';
 
 interface PackageJson {
   dependencies: Record<string, string>;
 }
 
+/**
+ * Sorts the keys of the given object.
+ * @returns A new object instance with sorted keys
+ */
+function sortObjectByKeys(obj: Record<string, string>) {
+  return Object.keys(obj)
+    .sort()
+    .reduce(
+      (result, key) => {
+        result[key] = obj[key];
+        return result;
+      },
+      {} as Record<string, string>,
+    );
+}
+
+/** Adds a package to the package.json in the given host tree. */
+export function addPackageToPackageJson(host: Tree, pkg: string, version: string): Tree {
+  if (host.exists('package.json')) {
+    const sourceText = host.read('package.json')!.toString('utf-8');
+    const json = JSON.parse(sourceText) as PackageJson;
+
+    if (!json.dependencies) {
+      json.dependencies = {};
+    }
+
+    if (!json.dependencies[pkg]) {
+      json.dependencies[pkg] = version;
+      json.dependencies = sortObjectByKeys(json.dependencies);
+    }
+
+    host.overwrite('package.json', JSON.stringify(json, null, 2));
+  }
+
+  return host;
+}
+
 describe('CDK ng-add', () => {
   let runner: SchematicTestRunner;
   let appTree: Tree;

src/cdk/schematics/ng-add/index.ts

@@ -6,9 +6,8 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import {Rule, SchematicContext, Tree} from '@angular-devkit/schematics';
-import {NodePackageInstallTask} from '@angular-devkit/schematics/tasks';
-import {addPackageToPackageJson, getPackageVersionFromPackageJson} from './package-config';
+import {Rule} from '@angular-devkit/schematics';
+import {addDependency, ExistingBehavior} from '@schematics/angular/utility';
 
 /**
  * Schematic factory entry-point for the `ng-add` schematic. The ng-add schematic will be
@@ -19,21 +18,14 @@ import {addPackageToPackageJson, getPackageVersionFromPackageJson} from './packa
  * this ensures that there will be no error that says that the CDK does not support `ng add`.
  */
 export default function (): Rule {
-  return (host: Tree, context: SchematicContext) => {
-    // The CLI inserts `@angular/cdk` into the `package.json` before this schematic runs. This
-    // means that we do not need to insert the CDK into `package.json` files again. In some cases
-    // though, it could happen that this schematic runs outside of the CLI `ng add` command, or
-    // the CDK is only listed as a dev dependency. If that is the case, we insert a version based
-    // on the current build version (substituted version placeholder).
-    if (getPackageVersionFromPackageJson(host, '@angular/cdk') === null) {
-      // In order to align the CDK version with other Angular dependencies that are setup by
-      // `@schematics/angular`, we use tilde instead of caret. This is default for Angular
-      // dependencies in new CLI projects.
-      addPackageToPackageJson(host, '@angular/cdk', `~0.0.0-PLACEHOLDER`);
+  // The CLI inserts `@angular/cdk` into the `package.json` before this schematic runs. This
+  // means that we do not need to insert the CDK into `package.json` files again. In some cases
+  // though, it could happen that this schematic runs outside of the CLI `ng add` command, or
+  // the CDK is only listed as a dev dependency. If that is the case, we insert a version based
+  // on the current build version (substituted version placeholder).
 
-      // Add a task to run the package manager. This is necessary because we updated the
-      // workspace "package.json" file and we want lock files to reflect the new version range.
-      context.addTask(new NodePackageInstallTask());
-    }
-  };
+  // In order to align the CDK version with other Angular dependencies that are setup by
+  // `@schematics/angular`, we use tilde instead of caret. This is default for Angular
+  // dependencies in new CLI projects.
+  return addDependency('@angular/cdk', `~0.0.0-PLACEHOLDER`, {existing: ExistingBehavior.Skip});
 }