build: ensure schematic code runs as commonjs in NPM output

The CLI does not yet support running schematics as ESM. For this
we actually still emit CommonJS output for schematics. We need to
add a sub-directory `package.json` for the schematic folders though
as otherwise NodeJS would incorrectly treat the `.js` schematic files
as ESM due to the top-level package.json file setting `type: module`.

Author: devversion

src/cdk/schematics/BUILD.bazel

@@ -46,6 +46,7 @@ ts_library(
 # This package is intended to be combined into the main @angular/cdk package as a dep.
 pkg_npm(
     name = "npm_package",
+    srcs = ["package.json"],
     deps = [
         ":schematics",
         ":schematics_assets",

src/cdk/schematics/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}

src/material/schematics/BUILD.bazel

@@ -44,6 +44,7 @@ ts_library(
 # This package is intended to be combined into the main @angular/material package as a dep.
 pkg_npm(
     name = "npm_package",
+    srcs = ["package.json"],
     deps = [
         ":schematics",
         ":schematics_assets",

src/material/schematics/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}

tools/release-checks/npm-package-output/check-package.ts

@@ -2,7 +2,7 @@ import {error} from '@angular/dev-infra-private/ng-dev/utils/console';
 import * as chalk from 'chalk';
 import {existsSync} from 'fs';
 import {sync as glob} from 'glob';
-import {join} from 'path';
+import {basename, dirname, join} from 'path';
 
 import {
   checkCdkPackage,
@@ -63,6 +63,12 @@ export function checkReleasePackage(
   // Check each "package.json" file in the release output. We want to ensure
   // that there are no invalid file references in the entry-point definitions.
   packageJsonFiles.forEach(filePath => {
+    // A `package.json` file part of the schematics folder is not considered an
+    // entry-point `package.json` file and does not need to be checked.
+    if (basename(dirname(filePath)) === 'schematics') {
+      return;
+    }
+
     checkEntryPointPackageJsonFile(filePath).forEach(message => addFailure(message, filePath));
   });