Template type checking re-builds do not run correctly when referencing a re-exported type

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
angular, typescript
Domain
build-system

Research direction

Start with the linked minimal reproduction and run ng serve with template type checking enabled on the stated Angular and Node versions. Change MyType between the abc and abcd definitions, then inspect the Angular CLI rebuild and template type-checking paths. Done means reverting the type definition removes the template error on rebuild.

Written by the indexing model from the issue text.

Description

area: @ngtools/webpack needs: investigation
Which @angular/* package(s) are the source of the bug?

Don't known / other

Is this a regression?

Yes

Description

Consider the following example, running ng serve with template type checking turned on:

  • An Angular template references a property on the component class in an expression.
  • This component class properties type definition comes from a file which re-exports the type definition from another file.
  • Re-builds do not always re-compile the template expression when they should.

More specifically, in the reproduction repo this looks as follows:

  • The app component template includes an expression: {{ myType?.abc }}.
  • The app component class defines the myType property: myType?: MyTypeReExported.
  • The type of the myType property comes from a file which re-exports another type. export type MyTypeRexported = MyType.
  • The type MyType comes from a file which defines the definition as: export interface MyType { abc: 123; }.
  • The initial ng serve will run without errors.
  • Changing the type definition of MyType to be export interface MyType { abcd: 123; } causes an error in the app component's template. This is seen in the re-build console output. This is the correct behaviour.
  • Changing the type definition back to what it was originally should remove the error. However, it does not. That is the bug.
Please provide a link to a minimal reproduction of the bug

https://github.com/HazzMan2409/angular-template-rebuild-bug

Please provide the environment you discovered this bug in
Angular 12.2.5.
Node 14.17.6

See the package.json on the repo for more details. At the time 12.2.5 was the latest version.
Dominant language
TypeScript
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