Error building with ng build --prod. Fine without --prod flag and ng serve

Question

I have a project that built fine with ng build --prod until I upgraded the version of TypeScript from 2.72 to 2.92 in my package.json.

After upgrading, I now get the following error:

ERROR in Cannot read property 'Symbol(Symbol.iterator)' of undefined

However, the project builds fine using ng build and runs fine using ng serve so I have no idea where this problem is occurring and the error doesn't tell me where the problem is in my project.

Answer 1

I found the issue. Using resolveJsonModule seems to be the issue as pointed out via this issue on Github: https://github.com/angular/angular/issues/25456

Exact same error. Really surprised that this hasn't been fixed properly.

Problem was I had no clue what the problem was as the error message was so vague. Commenting out my json import in my app.module made the build work as intended.