fix(upgrade): add try/catch when downgrading injectables (#38671)

This commit improves the error thrown by the downgrade module with a more
descriptive message on why the downgrade is failing.

Closes #37579

PR Close #38671

packages/upgrade/src/common/src/downgrade_injectable.ts

@@ -79,8 +79,12 @@ export function downgradeInjectable(token: any, downgradedModule: string = ''):
 
     validateInjectionKey($injector, downgradedModule, injectorKey, attemptedAction);
 
-    const injector: Injector = $injector.get(injectorKey);
-    return injector.get(token);
+    try {
+      const injector: Injector = $injector.get(injectorKey);
+      return injector.get(token);
+    } catch (err) {
+      throw new Error(`Error while ${attemptedAction}: ${err.message || err}`);
+    }
   };
   (factory as any)['$inject'] = [$INJECTOR];
 

packages/upgrade/src/common/test/downgrade_injectable_spec.ts

@@ -48,4 +48,16 @@ describe('downgradeInjectable', () => {
     expect(factory(mockNg1Injector)).toEqual('service value');
     expect(mockNg2Injector.get).toHaveBeenCalledWith('someToken');
   });
+
+  it('should mention the injectable\'s name in the error thrown when failing to retrieve injectable',
+     () => {
+       const factory = downgradeInjectable('someToken');
+       expect(factory).toEqual(jasmine.any(Function));
+       expect((factory as any).$inject).toEqual([$INJECTOR]);
+
+       const {mockNg1Injector, mockNg2Injector} = setupMockInjectors();
+       mockNg2Injector.get.and.throwError('Mock failure');
+       expect(() => factory(mockNg1Injector))
+           .toThrowError(/^Error while instantiating injectable 'someToken': Mock failure/);
+     });
 });