ng newにてThe Schematic workflow failed.

エラー解決

What

ng newコマンド実行時、以下のエラー群が発生しました。

⠏ Installing packages...npm WARN deprecated tslint@6.1.2: TSLint has been deprecated in favor of ESLint. Please see https://github.com/palantir/tslint/issues/4534 for more information.
npm WARN deprecated chokidar@2.1.8: Upgrade to chokidar 3 with 15x less dependencies. Chokidar 2 will break on node v14.
npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
npm ERR! Unexpected end of JSON input while parsing near '...://registry.npmjs.org'

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/apple/.npm/_logs/2020-07-03T13_33_59_631Z-debug.log
✖ Package install failed, see above.
The Schematic workflow failed. See above.

この状態で、ng serveを実行すると以下のエラーが発生します。

An unhandled exception occurred: Cannot find module '@angular-devkit/build-angular/package.json'
Require stack:
- /Users/apple/.config/yarn/global/node_modules/@angular-devkit/architect/node/node-modules-architect-host.js
- /Users/apple/.config/yarn/global/node_modules/@angular-devkit/architect/node/index.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/models/architect-command.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/commands/serve-impl.js
- /Users/apple/.config/yarn/global/node_modules/@angular-devkit/schematics/tools/export-ref.js
- /Users/apple/.config/yarn/global/node_modules/@angular-devkit/schematics/tools/index.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/utilities/json-schema.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/models/command-runner.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/lib/cli/index.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/lib/init.js
- /Users/apple/.config/yarn/global/node_modules/@angular/cli/bin/ng
See "/private/var/folders/yt/wcyrx93n3jd93smbhblqjrx40000gn/T/ng-TtYLQM/angular-errors.log" for further details.

Solution

Cannot find module '@angular-devkit/build-angular/package.json'とのことなので、以下のコマンドで@angular-devkit/build-angularを導入します。これで、ng newおよびng serveでのエラーが解決されました。

yarn add @angular-devkit/build-angular --dev

もし、npmの認証系でエラーが生じるなら以下も実行しておきます (下記の記事も参考になりました)。

$ sudo chown -R $(whoami) $(npm config get prefix)/{lib/node_modules,bin,share}

[参考] qiita.com