Unsupported private class error doesn't throw on building library for production

Bắt đầu bằng cách tái hiện quá trình build thư viện với ng b và ng b --prod bằng các lệnh và repository thư viện kiểm thử được mô tả trong issue. So sánh các entry point của bản build thông thường và bản build production liên quan đến public API của thư viện và việc kiểm tra private class; hoàn tất khi cả hai lệnh đều báo lỗi Unsupported private class.

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

i'm not sure

Description

when i export a component in the library module but not in the public API
the build command throw errors only in normal mode, but in production mode it completes successfully

🔬 Minimal Reproduction

clone https://github.com/robertIsaac/test-library
and run ng b and ng b --prod

or generate from scratch

ng new test-library --create-application=false
cd test-library
ng generate library test-library
ng g c test-export --export
ng b
ng b --prod

🔥 Exception or Error

both commands should throw the following error

Unsupported private class TestExportComponent. This class is visible to consumers via TestLibraryModule -> TestExportComponent, but is not exported from the top-level library entrypoint.

🌍 Your Environment

$ ng version

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/
    

Angular CLI: 9.1.1
Node: 12.14.1
OS: win32 x64

Angular: 9.1.2
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                            Version
------------------------------------------------------------
@angular-devkit/architect          0.901.1
@angular-devkit/build-angular      0.901.1
@angular-devkit/build-ng-packagr   0.901.1
@angular-devkit/build-optimizer    0.901.1
@angular-devkit/build-webpack      0.901.1
@angular-devkit/core               9.1.1
@angular-devkit/schematics         9.1.1
@angular/cli                       9.1.1
@ngtools/webpack                   9.1.1
@schematics/angular                9.1.1
@schematics/update                 0.901.1
ng-packagr                         9.1.1
rxjs                               6.5.5
typescript                         3.8.3
webpack                            4.42.0

Anything else relevant?

it would be nice if --export command also update the public api file if it's running inside a library