[Ivy - 9.0.0-rc.1] Running `ngc` on a custom library throws error "Appears in the NgModule.imports of ..., but could not be resolved to an NgModule class"

🐞 bug report

Affected Package

@angular/common but I expect that others can also have this issue.

Is this a regression?

Yes, running ngc on a code of a library that uses Angular’s packages has always works and the correct .metadata.json files have been created.

Description

Running ngc to generate the metadata.json of my custom library’s source code fails when using the latest 9.0.0.x release, currently available in the @next tag at npm.

I am testing how to building my package will work when 9.0.0 comes out.

🔬 Minimal Reproduction

As this requires compiling with ngc I have prepared a very simply package and you can download it here ngc issue.zip

Simply do the following:

• Extract the archive and open it in a terminal
• Install the npm packages with npm install
• Trigger ngc by executing ./node_modules/.bin/ngc

The following error is thrown:

🔥 Exception or Error

node_modules/@angular/common/common.d.ts:115:22 - error NG6002: Appears in the NgModule.imports of MyCommonModule, but could not be resolved to an NgModule class

115 export declare class CommonModule {
                         ~~~~~~~~~~~~
node_modules/@angular/common/common.d.ts:115:22 - error NG6003: Appears in the NgModule.exports of MyCommonModule, but could not be resolved to an NgModule, Component, Directive, or Pipe class

115 export declare class CommonModule {
                         ~~~~~~~~~~~~

🌍 Your Environment

Angular Version:

Angular CLI: 9.0.0-rc.1
Node: 10.15.2
OS: darwin x64
Angular: 9.0.0-rc.1
... common, compiler, compiler-cli, core

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.900.0-rc.1 (cli-only)
@angular-devkit/core         9.0.0-rc.1 (cli-only)
@angular-devkit/schematics   9.0.0-rc.1 (cli-only)
@schematics/angular          9.0.0-rc.1 (cli-only)
@schematics/update           0.900.0-rc.1 (cli-only)
rxjs                         6.5.3
typescript                   3.6.4

Anything else relevant? I am hitting this error in preparation for Ivy and 9.0.0 of my custom Angular library. I would love some assistance before 9.0.0 is live because at the moment I cannot build my custom library when using Angular packages 9.0.0

[alexzuza]

@VladimirAmiorkov Ivy compiler is default compiler since 9.0.0-next.3(https://github.com/angular/angular/blob/master/CHANGELOG.md#breaking-changes-8). If you want to compile your library in ViewEngine mode then I would suggest you using enableIvy option in your tsconfig.json

"angularCompilerOptions": {
      "genDir": ".",
      "skipMetadataEmit": false,
      "skipTemplateCodegen": true,
      "strictMetadataEmit": true,
      "enableIvy": false   <------------------ try this
    },

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