error NG1010: Value at position 0 in the NgModule.declarations of Module is not a reference

[kumaresan-subramani]

🐞 Bug report

If I do a postinstall ngcc I get the following errors in our library

Error: Failed to compile entry-point @syncfusion/ej2-angular-calendars (main as umd) due to compilation errors:
node_modules/@syncfusion/ej2-angular-calendars/dist/ej2-angular-calendars.umd.js:174:31 - error NG1010: Value at position 0 in the NgModule.declarations of CalendarModule is not a reference
  Value could not be determined statically.

174                 declarations: [
                                  ~
175                     exports.CalendarComponent
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
176                 ],
    ~~~~~~~~~~~~~~~~~

  node_modules/@syncfusion/ej2-angular-calendars/dist/ej2-angular-calendars.umd.js:175:21
    175                     exports.CalendarComponent
                            ~~~~~~~~~~~~~~~~~~~~~~~~~
    Unable to evaluate statically.
node_modules/@syncfusion/ej2-angular-calendars/dist/ej2-angular-calendars.umd.js:166:5 - error NG6002: Appears in the NgModule.imports of CalendarAllModule, but could not be resolved to an NgModule class.

Is it missing an @NgModule annotation?

166 var CalendarModule = /** @class */ (function () {
        ~~~~~~~~~~~~~~
node_modules/@syncfusion/ej2-angular-calendars/dist/ej2-angular-calendars.umd.js:166:5 - error NG6003: Appears in the NgModule.exports of CalendarAllModule, but could not be resolved to an NgModule, Component, Directive, or Pipe class.

Is it missing an Angular annotation?

Is this a regression?

Working fine with out "postinstall": "ngcc"

🔬 Minimal Reproduction

1. download my sample - https://github.com/kumaresan-subramani/Syncfusion-Calendar-Error-1

2. then give npm i or yarn i

My reported issue will occurs.

🔥 Exception or Error

🌍 Your Environment

    "@angular/animations": "~10.1.0",
    "@angular/common": "~10.1.0",
    "@angular/compiler": "~10.1.0",
    "@angular/core": "~10.1.0",
    "@angular/forms": "~10.1.0",
    "@angular/platform-browser": "~10.1.0",
    "@angular/platform-browser-dynamic": "~10.1.0",
    "@angular/router": "~10.1.0",
    "@angular-devkit/build-angular": "~0.1001.0",
    "@angular/cli": "~10.1.0",
    "@angular/compiler-cli": "~10.1.0",

Anything else relevant?
I have done some researching and found that below issue and tried everything which are reported in those issues but no luck for me.

#35255 (comment) - downgraded ts version same error
#36673 (comment) - tried changed my module declaration

This is our component config -

https://github.com/syncfusion/ej2-angular-ui-components/tree/master/components/calendars/src/calendar

Note: i am using ng-packagr to generate my angular library

[petebacondarwin]

So the reason for this error is that ngcc does not currently support parsing UMD/CommonJS properties of the form exports.Xxxx. It doesn't know how to interpret the exports identifier.

This is a bug in ngcc. The question is what priority we should give to fixing it.
Our experience is that UMD formats in libraries are usually not required for most use cases. Do you have concrete situations where this format is required?

As you said, if you just let the CLI do the work of running ngcc everything passes. This is because the CLI knows that your project does not need the UMD format, and just gets ngcc to process one of the other formats instead (e.g. ES2015).

By default running ngcc with no options will attempt to process every format of every package in node_modules. There are various ways to avoid this, such as adding the --first-only property or specifying a list of properties to consider (excluding main which maps to UMD) - e.g -p esm2015 esm5 module browser. Finally one can exclude the main property from just this package by adding a suitably configured ngcc.config.js file.

[kumaresan-subramani]

@petebacondarwin , i can understand but why umd files are generating while using ng-packagr to generate angular libraries even NGC wont compile this format since i need these umd files when i am having angular with systemjs application