message: test(language-service): external template update should not invalidate program
  In TypeScript 3.9, the compiler is able to re-use (i.e. not invalidate)
  the previous program if only external templates (i.e. no TS files) have
  changed.
  PR Close
diff: @@ -170,9 +170,10 @@ describe('TypeScriptServiceHost', () => {
  tsLSHost.override('/app/test.ng', '<div></div>');
  const newModules = ngLSHost.getAnalyzedModules();
  const newProgram = ngLSHost.program;
  - // Assert that the program has changed because external template was updated
  - expect(newProgram).not.toBe(oldProgram);
  - // But, analyzed modules should remain the same because none of the source
  + // The program should not have changed since external templates are not part of
  + // the TS source files. This is an improvement in TS 3.9 over previous versions.
  + expect(newProgram).toBe(oldProgram);
  + // And also analyzed modules should remain the same because none of the source
  // files have changed.
  expect(newModules).toBe(oldModules);
  });
  