'Angular 9 compilation errors after migration from Angular 8

I migrated my angular app from version 8 to 9. After running ng serve --open, my app opens in the browser and gets stuck at the loading screen with this error in the console window:

core.js:610 Uncaught Error: Angular JIT compilation failed: '@angular/compiler' not loaded!
  - JIT compilation is discouraged for production use-cases! Consider AOT mode instead.
  - Did you bootstrap using '@angular/platform-browser-dynamic' or '@angular/platform-server'?
  - Alternatively provide the compiler with 'import "@angular/compiler";' before bootstrapping.
    at getCompilerFacade (core.js:610)
    at Function.get (core.js:38351)
    at getNgModuleDef (core.js:2195)
    at assertNgModuleType (core.js:2933)
    at compileNgModuleFactory__POST_R3__ (core.js:41373)
    at PlatformRef.bootstrapModule (core.js:41740)
    at Module../src/main.ts (main.ts:11)
    at __webpack_require__ (bootstrap:79)
    at Object.0 (main.ts:13)
    at __webpack_require__ (bootstrap:79)


Solution 1:[1]

Check in app.module.ts if you are missing module...For example some times in module file people import HttpClient instead of HttpClientModule or it may be because of angular material for example people use MatButton instead of MatButtonModule sometimes which leads to this problem.

Solution 2:[2]

May be following command would work:

npm update

Or, you could try deleting node_modules folder and package-lock.json file and then executing the following command:

npm install

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Alish Madhukar
Solution 2 Salahuddin Ahmed