Merge remote-tracking branch 'contributions/fix-api-undefined-issue-7.6' into w2p-113560_edit-item-add-relationships-one-by-one

src/app/core/data/base/base-data.service.spec.ts

@@ -95,6 +95,7 @@ describe('BaseDataService', () => {
     remoteDataMocks = {
       RequestPending: new RemoteData(undefined, msToLive, timeStamp, RequestEntryState.RequestPending, undefined, undefined, undefined),
       ResponsePending: new RemoteData(undefined, msToLive, timeStamp, RequestEntryState.ResponsePending, undefined, undefined, undefined),
+      ResponsePendingStale: new RemoteData(undefined, msToLive, timeStamp, RequestEntryState.ResponsePendingStale, undefined, undefined, undefined),
       Success: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.Success, undefined, payload, statusCodeSuccess),
       SuccessStale: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.SuccessStale, undefined, payload, statusCodeSuccess),
       Error: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.Error, errorMessage, undefined, statusCodeError),
@@ -303,19 +304,21 @@ describe('BaseDataService', () => {
 
       it(`should not emit a cached stale RemoteData, but only start emitting after the state first changes to RequestPending`, () => {
         testScheduler.run(({ cold, expectObservable }) => {
-          spyOn(rdbService, 'buildSingle').and.returnValue(cold('a-b-c-d-e', {
+          spyOn(rdbService, 'buildSingle').and.returnValue(cold('a-b-c-d-e-f-g', {
-            a: remoteDataMocks.SuccessStale,
+            a: remoteDataMocks.ResponsePendingStale,
-            b: remoteDataMocks.RequestPending,
+            b: remoteDataMocks.SuccessStale,
-            c: remoteDataMocks.ResponsePending,
+            c: remoteDataMocks.ErrorStale,
-            d: remoteDataMocks.Success,
+            d: remoteDataMocks.RequestPending,
-            e: remoteDataMocks.SuccessStale,
+            e: remoteDataMocks.ResponsePending,
+            f: remoteDataMocks.Success,
+            g: remoteDataMocks.SuccessStale,
           }));
-          const expected = '--b-c-d-e';
+          const expected = '------d-e-f-g';
           const values = {
-            b: remoteDataMocks.RequestPending,
+            d: remoteDataMocks.RequestPending,
-            c: remoteDataMocks.ResponsePending,
+            e: remoteDataMocks.ResponsePending,
-            d: remoteDataMocks.Success,
+            f: remoteDataMocks.Success,
-            e: remoteDataMocks.SuccessStale,
+            g: remoteDataMocks.SuccessStale,
           };
 
           expectObservable(service.findByHref(selfLink, true, true, ...linksToFollow)).toBe(expected, values);
@@ -354,19 +357,21 @@ describe('BaseDataService', () => {
 
       it(`should not emit a cached stale RemoteData, but only start emitting after the state first changes to RequestPending`, () => {
         testScheduler.run(({ cold, expectObservable }) => {
-          spyOn(rdbService, 'buildSingle').and.returnValue(cold('a-b-c-d-e', {
+          spyOn(rdbService, 'buildSingle').and.returnValue(cold('a-b-c-d-e-f-g', {
-            a: remoteDataMocks.SuccessStale,
+            a: remoteDataMocks.ResponsePendingStale,
-            b: remoteDataMocks.RequestPending,
+            b: remoteDataMocks.SuccessStale,
-            c: remoteDataMocks.ResponsePending,
+            c: remoteDataMocks.ErrorStale,
-            d: remoteDataMocks.Success,
+            d: remoteDataMocks.RequestPending,
-            e: remoteDataMocks.SuccessStale,
+            e: remoteDataMocks.ResponsePending,
+            f: remoteDataMocks.Success,
+            g: remoteDataMocks.SuccessStale,
           }));
-          const expected = '--b-c-d-e';
+          const expected = '------d-e-f-g';
           const values = {
-            b: remoteDataMocks.RequestPending,
+            d: remoteDataMocks.RequestPending,
-            c: remoteDataMocks.ResponsePending,
+            e: remoteDataMocks.ResponsePending,
-            d: remoteDataMocks.Success,
+            f: remoteDataMocks.Success,
-            e: remoteDataMocks.SuccessStale,
+            g: remoteDataMocks.SuccessStale,
           };
 
           expectObservable(service.findByHref(selfLink, false, true, ...linksToFollow)).toBe(expected, values);
@@ -487,19 +492,21 @@ describe('BaseDataService', () => {
 
       it(`should not emit a cached stale RemoteData, but only start emitting after the state first changes to RequestPending`, () => {
         testScheduler.run(({ cold, expectObservable }) => {
-          spyOn(rdbService, 'buildList').and.returnValue(cold('a-b-c-d-e', {
+          spyOn(rdbService, 'buildList').and.returnValue(cold('a-b-c-d-e-f-g', {
-            a: remoteDataMocks.SuccessStale,
+            a: remoteDataMocks.ResponsePendingStale,
-            b: remoteDataMocks.RequestPending,
+            b: remoteDataMocks.SuccessStale,
-            c: remoteDataMocks.ResponsePending,
+            c: remoteDataMocks.ErrorStale,
-            d: remoteDataMocks.Success,
+            d: remoteDataMocks.RequestPending,
-            e: remoteDataMocks.SuccessStale,
+            e: remoteDataMocks.ResponsePending,
+            f: remoteDataMocks.Success,
+            g: remoteDataMocks.SuccessStale,
           }));
-          const expected = '--b-c-d-e';
+          const expected = '------d-e-f-g';
           const values = {
-            b: remoteDataMocks.RequestPending,
+            d: remoteDataMocks.RequestPending,
-            c: remoteDataMocks.ResponsePending,
+            e: remoteDataMocks.ResponsePending,
-            d: remoteDataMocks.Success,
+            f: remoteDataMocks.Success,
-            e: remoteDataMocks.SuccessStale,
+            g: remoteDataMocks.SuccessStale,
           };
 
           expectObservable(service.findListByHref(selfLink, findListOptions, true, true, ...linksToFollow)).toBe(expected, values);
@@ -538,21 +545,24 @@ describe('BaseDataService', () => {
 
       it(`should not emit a cached stale RemoteData, but only start emitting after the state first changes to RequestPending`, () => {
         testScheduler.run(({ cold, expectObservable }) => {
-          spyOn(rdbService, 'buildList').and.returnValue(cold('a-b-c-d-e', {
+          spyOn(rdbService, 'buildList').and.returnValue(cold('a-b-c-d-e-f-g', {
-            a: remoteDataMocks.SuccessStale,
+            a: remoteDataMocks.ResponsePendingStale,
-            b: remoteDataMocks.RequestPending,
+            b: remoteDataMocks.SuccessStale,
-            c: remoteDataMocks.ResponsePending,
+            c: remoteDataMocks.ErrorStale,
-            d: remoteDataMocks.Success,
+            d: remoteDataMocks.RequestPending,
-            e: remoteDataMocks.SuccessStale,
+            e: remoteDataMocks.ResponsePending,
+            f: remoteDataMocks.Success,
+            g: remoteDataMocks.SuccessStale,
           }));
-          const expected = '--b-c-d-e';
+          const expected = '------d-e-f-g';
           const values = {
-            b: remoteDataMocks.RequestPending,
+            d: remoteDataMocks.RequestPending,
-            c: remoteDataMocks.ResponsePending,
+            e: remoteDataMocks.ResponsePending,
-            d: remoteDataMocks.Success,
+            f: remoteDataMocks.Success,
-            e: remoteDataMocks.SuccessStale,
+            g: remoteDataMocks.SuccessStale,
           };
 
+
           expectObservable(service.findListByHref(selfLink, findListOptions, false, true, ...linksToFollow)).toBe(expected, values);
         });
       });

src/app/core/data/base/base-data.service.ts

@@ -273,7 +273,7 @@ export class BaseDataService<T extends CacheableObject> implements HALDataServic
       // call it isn't immediately returned, but we wait until the remote data for the new request
       // is created. If useCachedVersionIfAvailable is false it also ensures you don't get a
       // cached completed object
-      skipWhile((rd: RemoteData<T>) => useCachedVersionIfAvailable ? rd.isStale : rd.hasCompleted),
+      skipWhile((rd: RemoteData<T>) => rd.isStale || (!useCachedVersionIfAvailable && rd.hasCompleted)),
       this.reRequestStaleRemoteData(reRequestOnStale, () =>
         this.findByHref(href$, useCachedVersionIfAvailable, reRequestOnStale, ...linksToFollow)),
     );
@@ -307,7 +307,7 @@ export class BaseDataService<T extends CacheableObject> implements HALDataServic
       // call it isn't immediately returned, but we wait until the remote data for the new request
       // is created. If useCachedVersionIfAvailable is false it also ensures you don't get a
       // cached completed object
-      skipWhile((rd: RemoteData<PaginatedList<T>>) => useCachedVersionIfAvailable ? rd.isStale : rd.hasCompleted),
+      skipWhile((rd: RemoteData<PaginatedList<T>>) => rd.isStale || (!useCachedVersionIfAvailable && rd.hasCompleted)),
       this.reRequestStaleRemoteData(reRequestOnStale, () =>
         this.findListByHref(href$, options, useCachedVersionIfAvailable, reRequestOnStale, ...linksToFollow)),
     );

src/app/core/data/request-entry-state.model.spec.ts

@@ -0,0 +1,186 @@
+import {
+  isRequestPending,
+  isError,
+  isSuccess,
+  isErrorStale,
+  isSuccessStale,
+  isResponsePending,
+  isResponsePendingStale,
+  isLoading,
+  isStale,
+  hasFailed,
+  hasSucceeded,
+  hasCompleted,
+  RequestEntryState
+} from './request-entry-state.model';
+
+describe(`isRequestPending`, () => {
+  it(`should only return true if the given state is RequestPending`, () => {
+    expect(isRequestPending(RequestEntryState.RequestPending)).toBeTrue();
+
+    expect(isRequestPending(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isRequestPending(RequestEntryState.Error)).toBeFalse();
+    expect(isRequestPending(RequestEntryState.Success)).toBeFalse();
+    expect(isRequestPending(RequestEntryState.ResponsePendingStale)).toBeFalse();
+    expect(isRequestPending(RequestEntryState.ErrorStale)).toBeFalse();
+    expect(isRequestPending(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`isError`, () => {
+  it(`should only return true if the given state is Error`, () => {
+    expect(isError(RequestEntryState.Error)).toBeTrue();
+
+    expect(isError(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isError(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isError(RequestEntryState.Success)).toBeFalse();
+    expect(isError(RequestEntryState.ResponsePendingStale)).toBeFalse();
+    expect(isError(RequestEntryState.ErrorStale)).toBeFalse();
+    expect(isError(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`isSuccess`, () => {
+  it(`should only return true if the given state is Success`, () => {
+    expect(isSuccess(RequestEntryState.Success)).toBeTrue();
+
+    expect(isSuccess(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isSuccess(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isSuccess(RequestEntryState.Error)).toBeFalse();
+    expect(isSuccess(RequestEntryState.ResponsePendingStale)).toBeFalse();
+    expect(isSuccess(RequestEntryState.ErrorStale)).toBeFalse();
+    expect(isSuccess(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`isErrorStale`, () => {
+  it(`should only return true if the given state is ErrorStale`, () => {
+    expect(isErrorStale(RequestEntryState.ErrorStale)).toBeTrue();
+
+    expect(isErrorStale(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isErrorStale(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isErrorStale(RequestEntryState.Error)).toBeFalse();
+    expect(isErrorStale(RequestEntryState.Success)).toBeFalse();
+    expect(isErrorStale(RequestEntryState.ResponsePendingStale)).toBeFalse();
+    expect(isErrorStale(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`isSuccessStale`, () => {
+  it(`should only return true if the given state is SuccessStale`, () => {
+    expect(isSuccessStale(RequestEntryState.SuccessStale)).toBeTrue();
+
+    expect(isSuccessStale(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isSuccessStale(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isSuccessStale(RequestEntryState.Error)).toBeFalse();
+    expect(isSuccessStale(RequestEntryState.Success)).toBeFalse();
+    expect(isSuccessStale(RequestEntryState.ResponsePendingStale)).toBeFalse();
+    expect(isSuccessStale(RequestEntryState.ErrorStale)).toBeFalse();
+  });
+});
+
+describe(`isResponsePending`, () => {
+  it(`should only return true if the given state is ResponsePending`, () => {
+    expect(isResponsePending(RequestEntryState.ResponsePending)).toBeTrue();
+
+    expect(isResponsePending(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isResponsePending(RequestEntryState.Error)).toBeFalse();
+    expect(isResponsePending(RequestEntryState.Success)).toBeFalse();
+    expect(isResponsePending(RequestEntryState.ResponsePendingStale)).toBeFalse();
+    expect(isResponsePending(RequestEntryState.ErrorStale)).toBeFalse();
+    expect(isResponsePending(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`isResponsePendingStale`, () => {
+  it(`should only return true if the given state is requestPending`, () => {
+    expect(isResponsePendingStale(RequestEntryState.ResponsePendingStale)).toBeTrue();
+
+    expect(isResponsePendingStale(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isResponsePendingStale(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isResponsePendingStale(RequestEntryState.Error)).toBeFalse();
+    expect(isResponsePendingStale(RequestEntryState.Success)).toBeFalse();
+    expect(isResponsePendingStale(RequestEntryState.ErrorStale)).toBeFalse();
+    expect(isResponsePendingStale(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`isLoading`, () => {
+  it(`should only return true if the given state is RequestPending, ResponsePending or ResponsePendingStale`, () => {
+    expect(isLoading(RequestEntryState.RequestPending)).toBeTrue();
+    expect(isLoading(RequestEntryState.ResponsePending)).toBeTrue();
+    expect(isLoading(RequestEntryState.ResponsePendingStale)).toBeTrue();
+
+    expect(isLoading(RequestEntryState.Error)).toBeFalse();
+    expect(isLoading(RequestEntryState.Success)).toBeFalse();
+    expect(isLoading(RequestEntryState.ErrorStale)).toBeFalse();
+    expect(isLoading(RequestEntryState.SuccessStale)).toBeFalse();
+  });
+});
+
+describe(`hasFailed`, () => {
+  describe(`when the state is loading`, () => {
+    it(`should return undefined`, () => {
+      expect(hasFailed(RequestEntryState.RequestPending)).toBeUndefined();
+      expect(hasFailed(RequestEntryState.ResponsePending)).toBeUndefined();
+      expect(hasFailed(RequestEntryState.ResponsePendingStale)).toBeUndefined();
+    });
+  });
+
+  describe(`when the state has completed`, () => {
+    it(`should only return true if the given state is Error or ErrorStale`, () => {
+      expect(hasFailed(RequestEntryState.Error)).toBeTrue();
+      expect(hasFailed(RequestEntryState.ErrorStale)).toBeTrue();
+
+      expect(hasFailed(RequestEntryState.Success)).toBeFalse();
+      expect(hasFailed(RequestEntryState.SuccessStale)).toBeFalse();
+    });
+  });
+});
+
+describe(`hasSucceeded`, () => {
+  describe(`when the state is loading`, () => {
+    it(`should return undefined`, () => {
+      expect(hasSucceeded(RequestEntryState.RequestPending)).toBeUndefined();
+      expect(hasSucceeded(RequestEntryState.ResponsePending)).toBeUndefined();
+      expect(hasSucceeded(RequestEntryState.ResponsePendingStale)).toBeUndefined();
+    });
+  });
+
+  describe(`when the state has completed`, () => {
+    it(`should only return true if the given state is Error or ErrorStale`, () => {
+      expect(hasSucceeded(RequestEntryState.Success)).toBeTrue();
+      expect(hasSucceeded(RequestEntryState.SuccessStale)).toBeTrue();
+
+      expect(hasSucceeded(RequestEntryState.Error)).toBeFalse();
+      expect(hasSucceeded(RequestEntryState.ErrorStale)).toBeFalse();
+    });
+  });
+});
+
+
+describe(`hasCompleted`, () => {
+  it(`should only return true if the given state is Error, Success, ErrorStale or SuccessStale`, () => {
+    expect(hasCompleted(RequestEntryState.Error)).toBeTrue();
+    expect(hasCompleted(RequestEntryState.Success)).toBeTrue();
+    expect(hasCompleted(RequestEntryState.ErrorStale)).toBeTrue();
+    expect(hasCompleted(RequestEntryState.SuccessStale)).toBeTrue();
+
+    expect(hasCompleted(RequestEntryState.RequestPending)).toBeFalse();
+    expect(hasCompleted(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(hasCompleted(RequestEntryState.ResponsePendingStale)).toBeFalse();
+  });
+});
+
+describe(`isStale`, () => {
+  it(`should only return true if the given state is ResponsePendingStale, SuccessStale or ErrorStale`, () => {
+    expect(isStale(RequestEntryState.ResponsePendingStale)).toBeTrue();
+    expect(isStale(RequestEntryState.SuccessStale)).toBeTrue();
+    expect(isStale(RequestEntryState.ErrorStale)).toBeTrue();
+
+    expect(isStale(RequestEntryState.RequestPending)).toBeFalse();
+    expect(isStale(RequestEntryState.ResponsePending)).toBeFalse();
+    expect(isStale(RequestEntryState.Error)).toBeFalse();
+    expect(isStale(RequestEntryState.Success)).toBeFalse();
+  });
+});

src/app/core/data/request-entry-state.model.ts

@@ -3,8 +3,9 @@ export enum RequestEntryState {
   ResponsePending = 'ResponsePending',
   Error = 'Error',
   Success = 'Success',
+  ResponsePendingStale = 'ResponsePendingStale',
   ErrorStale = 'ErrorStale',
-  SuccessStale = 'SuccessStale'
+  SuccessStale = 'SuccessStale',
 }
 
 /**
@@ -42,12 +43,21 @@ export const isSuccessStale = (state: RequestEntryState) =>
  */
 export const isResponsePending = (state: RequestEntryState) =>
   state === RequestEntryState.ResponsePending;
+
 /**
- * Returns true if the given state is RequestPending or ResponsePending,
+ * Returns true if the given state is ResponsePendingStale, false otherwise
- * false otherwise
+ */
+export const isResponsePendingStale = (state: RequestEntryState) =>
+  state === RequestEntryState.ResponsePendingStale;
+
+/**
+ * Returns true if the given state is RequestPending, RequestPendingStale, ResponsePending, or
+ * ResponsePendingStale, false otherwise
  */
 export const isLoading = (state: RequestEntryState) =>
-  isRequestPending(state) || isResponsePending(state);
+  isRequestPending(state) ||
+  isResponsePending(state) ||
+  isResponsePendingStale(state);
 
 /**
  * If isLoading is true for the given state, this method returns undefined, we can't know yet.
@@ -82,7 +92,10 @@ export const hasCompleted = (state: RequestEntryState) =>
   !isLoading(state);
 
 /**
- * Returns true if the given state is SuccessStale or ErrorStale, false otherwise
+ * Returns true if the given state is isRequestPendingStale, isResponsePendingStale, SuccessStale or
+ * ErrorStale, false otherwise
  */
 export const isStale = (state: RequestEntryState) =>
-  isSuccessStale(state) || isErrorStale(state);
+  isResponsePendingStale(state) ||
+  isSuccessStale(state) ||
+  isErrorStale(state);

src/app/core/data/request.reducer.spec.ts

@@ -48,9 +48,16 @@ describe('requestReducer', () => {
       lastUpdated: 0
     }
   };
+  const testResponsePendingState = {
+    [id1]: {
+      state: RequestEntryState.ResponsePending,
+      lastUpdated: 0
+    }
+  };
   deepFreeze(testInitState);
   deepFreeze(testSuccessState);
   deepFreeze(testErrorState);
+  deepFreeze(testResponsePendingState);
 
   it('should return the current state when no valid actions have been made', () => {
     const action = new NullAction();
@@ -91,29 +98,94 @@ describe('requestReducer', () => {
     expect(newState[id1].response).toEqual(undefined);
   });
 
-  it('should set state to Success for the given RestRequest in the state, in response to a SUCCESS action', () => {
+  describe(`in response to a SUCCESS action`, () => {
-    const state = testInitState;
+    let startState;
+    describe(`when the entry isn't stale`, () => {
+      beforeEach(() => {
+        startState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.ResponsePending
+          })
+        });
+        deepFreeze(startState);
+      });
+      it('should set state to Success for the given RestRequest in the state', () => {
+        const action = new RequestSuccessAction(id1, 200);
+        const newState = requestReducer(startState, action);
 
-    const action = new RequestSuccessAction(id1, 200);
+        expect(newState[id1].request.uuid).toEqual(id1);
-    const newState = requestReducer(state, action);
+        expect(newState[id1].request.href).toEqual(link1);
+        expect(newState[id1].state).toEqual(RequestEntryState.Success);
+        expect(newState[id1].response.statusCode).toEqual(200);
+      });
+    });
+
+    describe(`when the entry is stale`, () => {
+      beforeEach(() => {
+        startState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.ResponsePendingStale
+          })
+        });
+        deepFreeze(startState);
+      });
+      it('should set state to SuccessStale for the given RestRequest in the state', () => {
+        const action = new RequestSuccessAction(id1, 200);
+        const newState = requestReducer(startState, action);
+
+        expect(newState[id1].request.uuid).toEqual(id1);
+        expect(newState[id1].request.href).toEqual(link1);
+        expect(newState[id1].state).toEqual(RequestEntryState.SuccessStale);
+        expect(newState[id1].response.statusCode).toEqual(200);
+      });
+    });
 
-    expect(newState[id1].request.uuid).toEqual(id1);
-    expect(newState[id1].request.href).toEqual(link1);
-    expect(newState[id1].state).toEqual(RequestEntryState.Success);
-    expect(newState[id1].response.statusCode).toEqual(200);
   });
 
-  it('should set state to Error for the given RestRequest in the state, in response to an ERROR action', () => {
+  describe(`in response to an ERROR action`, () => {
-    const state = testInitState;
+    let startState;
+    describe(`when the entry isn't stale`, () => {
+      beforeEach(() => {
+        startState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.ResponsePending
+          })
+        });
+        deepFreeze(startState);
+      });
+      it('should set state to Error for the given RestRequest in the state', () => {
+        const action = new RequestErrorAction(id1, 404, 'Not Found');
+        const newState = requestReducer(startState, action);
 
-    const action = new RequestErrorAction(id1, 404, 'Not Found');
+        expect(newState[id1].request.uuid).toEqual(id1);
-    const newState = requestReducer(state, action);
+        expect(newState[id1].request.href).toEqual(link1);
+        expect(newState[id1].state).toEqual(RequestEntryState.Error);
+        expect(newState[id1].response.statusCode).toEqual(404);
+        expect(newState[id1].response.errorMessage).toEqual('Not Found');
+      });
+    });
 
-    expect(newState[id1].request.uuid).toEqual(id1);
+    describe(`when the entry is stale`, () => {
-    expect(newState[id1].request.href).toEqual(link1);
+      beforeEach(() => {
-    expect(newState[id1].state).toEqual(RequestEntryState.Error);
+        startState = Object.assign({}, testInitState, {
-    expect(newState[id1].response.statusCode).toEqual(404);
+          [id1]: Object.assign({}, testInitState[id1], {
-    expect(newState[id1].response.errorMessage).toEqual('Not Found');
+            state: RequestEntryState.ResponsePendingStale
+          })
+        });
+        deepFreeze(startState);
+      });
+      it('should set state to ErrorStale for the given RestRequest in the state', () => {
+        const action = new RequestErrorAction(id1, 404, 'Not Found');
+        const newState = requestReducer(startState, action);
+
+        expect(newState[id1].request.uuid).toEqual(id1);
+        expect(newState[id1].request.href).toEqual(link1);
+        expect(newState[id1].state).toEqual(RequestEntryState.ErrorStale);
+        expect(newState[id1].response.statusCode).toEqual(404);
+        expect(newState[id1].response.errorMessage).toEqual('Not Found');
+      });
+
+    });
   });
 
   it('should update the response\'s timeCompleted for the given RestRequest in the state, in response to a RESET_TIMESTAMPS action', () => {
@@ -145,28 +217,112 @@ describe('requestReducer', () => {
     expect(newState[id1]).toBeNull();
   });
 
-  describe(`for an entry with state: Success`, () => {
+  describe(`in response to a STALE action`, () => {
-    it(`should set the state to SuccessStale, in response to a STALE action`, () => {
+    describe(`when the entry has been removed`, () => {
-      const state = testSuccessState;
+      it(`shouldn't do anything`, () => {
+        const startState = {
+          [id1]: null
+        };
+        deepFreeze(startState);
 
-      const action = new RequestStaleAction(id1);
+        const action = new RequestStaleAction(id1);
-      const newState = requestReducer(state, action);
+        const newState = requestReducer(startState, action);
 
-      expect(newState[id1].state).toEqual(RequestEntryState.SuccessStale);
+        expect(newState[id1]).toBeNull();
-      expect(newState[id1].lastUpdated).toBe(action.lastUpdated);
+      });
+    });
+
+    describe(`for stale entries`, () => {
+      it(`shouldn't do anything`, () => {
+        const rpsStartState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.ResponsePendingStale
+          })
+        });
+        deepFreeze(rpsStartState);
+
+        const action = new RequestStaleAction(id1);
+        let newState = requestReducer(rpsStartState, action);
+
+        expect(newState[id1].state).toEqual(rpsStartState[id1].state);
+        expect(newState[id1].lastUpdated).toBe(rpsStartState[id1].lastUpdated);
+
+        const ssStartState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.SuccessStale
+          })
+        });
+
+        newState = requestReducer(ssStartState, action);
+
+        expect(newState[id1].state).toEqual(ssStartState[id1].state);
+        expect(newState[id1].lastUpdated).toBe(ssStartState[id1].lastUpdated);
+
+        const esStartState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.ErrorStale
+          })
+        });
+
+        newState = requestReducer(esStartState, action);
+
+        expect(newState[id1].state).toEqual(esStartState[id1].state);
+        expect(newState[id1].lastUpdated).toBe(esStartState[id1].lastUpdated);
+
+      });
+    });
+
+    describe(`for and entry with state: RequestPending`, () => {
+      it(`shouldn't do anything`, () => {
+        const startState = Object.assign({}, testInitState, {
+          [id1]: Object.assign({}, testInitState[id1], {
+            state: RequestEntryState.RequestPending
+          })
+        });
+
+        const action = new RequestStaleAction(id1);
+        const newState = requestReducer(startState, action);
+
+        expect(newState[id1].state).toEqual(startState[id1].state);
+        expect(newState[id1].lastUpdated).toBe(startState[id1].lastUpdated);
+
+      });
+    });
+
+    describe(`for an entry with state: ResponsePending`, () => {
+      it(`should set the state to ResponsePendingStale`, () => {
+        const state = testResponsePendingState;
+
+        const action = new RequestStaleAction(id1);
+        const newState = requestReducer(state, action);
+
+        expect(newState[id1].state).toEqual(RequestEntryState.ResponsePendingStale);
+        expect(newState[id1].lastUpdated).toBe(action.lastUpdated);
+      });
+    });
+
+    describe(`for an entry with state: Success`, () => {
+      it(`should set the state to SuccessStale`, () => {
+        const state = testSuccessState;
+
+        const action = new RequestStaleAction(id1);
+        const newState = requestReducer(state, action);
+
+        expect(newState[id1].state).toEqual(RequestEntryState.SuccessStale);
+        expect(newState[id1].lastUpdated).toBe(action.lastUpdated);
+      });
+    });
+
+    describe(`for an entry with state: Error`, () => {
+      it(`should set the state to ErrorStale`, () => {
+        const state = testErrorState;
+
+        const action = new RequestStaleAction(id1);
+        const newState = requestReducer(state, action);
+
+        expect(newState[id1].state).toEqual(RequestEntryState.ErrorStale);
+        expect(newState[id1].lastUpdated).toBe(action.lastUpdated);
+      });
     });
   });
-
-  describe(`for an entry with state: Error`, () => {
-    it(`should set the state to ErrorStale, in response to a STALE action`, () => {
-      const state = testErrorState;
-
-      const action = new RequestStaleAction(id1);
-      const newState = requestReducer(state, action);
-
-      expect(newState[id1].state).toEqual(RequestEntryState.ErrorStale);
-      expect(newState[id1].lastUpdated).toBe(action.lastUpdated);
-    });
-  });
-
 });

src/app/core/data/request.reducer.ts

@@ -11,7 +11,13 @@ import {
   ResetResponseTimestampsAction
 } from './request.actions';
 import { isNull } from '../../shared/empty.util';
-import { hasSucceeded, isStale, RequestEntryState } from './request-entry-state.model';
+import {
+  hasSucceeded,
+  isStale,
+  RequestEntryState,
+  isRequestPending,
+  isResponsePending
+} from './request-entry-state.model';
 import { RequestState } from './request-state.model';
 
 // Object.create(null) ensures the object has no default js properties (e.g. `__proto__`)
@@ -91,14 +97,17 @@ function executeRequest(storeState: RequestState, action: RequestExecuteAction):
  *    the new storeState, with the response added to the request
  */
 function completeSuccessRequest(storeState: RequestState, action: RequestSuccessAction): RequestState {
-  if (isNull(storeState[action.payload.uuid])) {
+  const prevEntry = storeState[action.payload.uuid];
+  if (isNull(prevEntry)) {
     // after a request has been removed it's possible pending changes still come in.
     // Don't store them
     return storeState;
   } else {
     return Object.assign({}, storeState, {
-      [action.payload.uuid]: Object.assign({}, storeState[action.payload.uuid], {
+      [action.payload.uuid]: Object.assign({}, prevEntry, {
-        state: RequestEntryState.Success,
+        // If a response comes in for a request that's already stale, still store it otherwise
+        // components that are waiting for it might freeze
+        state: isStale(prevEntry.state) ? RequestEntryState.SuccessStale : RequestEntryState.Success,
         response: {
           timeCompleted: action.payload.timeCompleted,
           lastUpdated: action.payload.timeCompleted,
@@ -124,14 +133,17 @@ function completeSuccessRequest(storeState: RequestState, action: RequestSuccess
  *    the new storeState, with the response added to the request
  */
 function completeFailedRequest(storeState: RequestState, action: RequestErrorAction): RequestState {
-  if (isNull(storeState[action.payload.uuid])) {
+  const prevEntry = storeState[action.payload.uuid];
+  if (isNull(prevEntry)) {
     // after a request has been removed it's possible pending changes still come in.
     // Don't store them
     return storeState;
   } else {
     return Object.assign({}, storeState, {
-      [action.payload.uuid]: Object.assign({}, storeState[action.payload.uuid], {
+      [action.payload.uuid]: Object.assign({}, prevEntry, {
-        state: RequestEntryState.Error,
+        // If a response comes in for a request that's already stale, still store it otherwise
+        // components that are waiting for it might freeze
+        state: isStale(prevEntry.state) ? RequestEntryState.ErrorStale : RequestEntryState.Error,
         response: {
           timeCompleted: action.payload.timeCompleted,
           lastUpdated: action.payload.timeCompleted,
@@ -155,22 +167,27 @@ function completeFailedRequest(storeState: RequestState, action: RequestErrorAct
  *    the new storeState, set to stale
  */
 function expireRequest(storeState: RequestState, action: RequestStaleAction): RequestState {
-  if (isNull(storeState[action.payload.uuid])) {
+  const prevEntry = storeState[action.payload.uuid];
-    // after a request has been removed it's possible pending changes still come in.
+  if (isNull(prevEntry) || isStale(prevEntry.state) || isRequestPending(prevEntry.state)) {
-    // Don't store them
+    // No need to do anything if the entry doesn't exist, is already stale, or if the request is
+    // still pending, because that means it still needs to be sent to the server. Any response
+    // is guaranteed to have been generated after the request was set to stale.
     return storeState;
   } else {
-    const prevEntry = storeState[action.payload.uuid];
+    let nextRequestEntryState: RequestEntryState;
-    if (isStale(prevEntry.state)) {
+    if (isResponsePending(prevEntry.state)) {
-      return storeState;
+      nextRequestEntryState = RequestEntryState.ResponsePendingStale;
+    } else if (hasSucceeded(prevEntry.state)) {
+      nextRequestEntryState = RequestEntryState.SuccessStale;
     } else {
-      return Object.assign({}, storeState, {
+      nextRequestEntryState = RequestEntryState.ErrorStale;
-        [action.payload.uuid]: Object.assign({}, prevEntry, {
-          state: hasSucceeded(prevEntry.state) ? RequestEntryState.SuccessStale : RequestEntryState.ErrorStale,
-          lastUpdated: action.lastUpdated
-        })
-      });
     }
+    return Object.assign({}, storeState, {
+      [action.payload.uuid]: Object.assign({}, prevEntry, {
+        state: nextRequestEntryState,
+        lastUpdated: action.lastUpdated
+      })
+    });
   }
 }
 

src/app/core/data/request.service.spec.ts

@@ -638,4 +638,41 @@ describe('RequestService', () => {
       expect(done$).toBeObservable(cold('-----(t|)', { t: true }));
     }));
   });
+
+  describe('setStaleByHref', () => {
+    const uuid = 'c574a42c-4818-47ac-bbe1-6c3cd622c81f';
+    const href = 'https://rest.api/some/object';
+    const freshRE: any = {
+      request: { uuid, href },
+      state: RequestEntryState.Success
+    };
+    const staleRE: any = {
+      request: { uuid, href },
+      state: RequestEntryState.SuccessStale
+    };
+
+    it(`should call getByHref to retrieve the RequestEntry matching the href`, () => {
+      spyOn(service, 'getByHref').and.returnValue(observableOf(staleRE));
+      service.setStaleByHref(href);
+      expect(service.getByHref).toHaveBeenCalledWith(href);
+    });
+
+    it(`should dispatch a RequestStaleAction for the RequestEntry returned by getByHref`, (done: DoneFn) => {
+      spyOn(service, 'getByHref').and.returnValue(observableOf(staleRE));
+      spyOn(store, 'dispatch');
+      service.setStaleByHref(href).subscribe(() => {
+        expect(store.dispatch).toHaveBeenCalledWith(new RequestStaleAction(uuid));
+        done();
+      });
+    });
+
+   it(`should emit true when the request in the store is stale`, () => {
+     spyOn(service, 'getByHref').and.returnValue(cold('a-b', {
+       a: freshRE,
+       b: staleRE
+     }));
+     const result$ = service.setStaleByHref(href);
+     expect(result$).toBeObservable(cold('--(c|)', { c: true }));
+   });
+  });
 });

src/app/core/data/request.service.ts

@@ -16,7 +16,7 @@ import {
   RequestExecuteAction,
   RequestStaleAction
 } from './request.actions';
-import { GetRequest} from './request.models';
+import { GetRequest } from './request.models';
 import { CommitSSBAction } from '../cache/server-sync-buffer.actions';
 import { RestRequestMethod } from './rest-request-method';
 import { coreSelector } from '../core.selectors';
@@ -164,7 +164,7 @@ export class RequestService {
     this.getByHref(request.href).pipe(
       take(1))
       .subscribe((re: RequestEntry) => {
-        isPending = (hasValue(re) && isLoading(re.state));
+        isPending = (hasValue(re) && isLoading(re.state) && !isStale(re.state));
       });
     return isPending;
   }
@@ -331,7 +331,29 @@ export class RequestService {
       map((request: RequestEntry) => isStale(request.state)),
       filter((stale: boolean) => stale),
       take(1),
-      );
+    );
+  }
+
+  /**
+   * Mark a request as stale
+   * @param href  the href of the request
+   * @return      an Observable that will emit true once the Request becomes stale
+   */
+  setStaleByHref(href: string): Observable<boolean> {
+    const requestEntry$ = this.getByHref(href);
+
+    requestEntry$.pipe(
+      map((re: RequestEntry) => re.request.uuid),
+      take(1),
+    ).subscribe((uuid: string) => {
+      this.store.dispatch(new RequestStaleAction(uuid));
+    });
+
+    return requestEntry$.pipe(
+      map((request: RequestEntry) => isStale(request.state)),
+      filter((stale: boolean) => stale),
+      take(1)
+    );
   }
 
   /**
@@ -344,10 +366,10 @@ export class RequestService {
     // if it's not a GET request
     if (request.method !== RestRequestMethod.GET) {
       return true;
-    // if it is a GET request, check it isn't pending
+      // if it is a GET request, check it isn't pending
     } else if (this.isPending(request)) {
       return false;
-    // if it is pending, check if we're allowed to use a cached version
+      // if it is pending, check if we're allowed to use a cached version
     } else if (!useCachedVersionIfAvailable) {
       return true;
     } else {

src/app/core/data/root-data.service.spec.ts

@@ -1,16 +1,18 @@
 import { RootDataService } from './root-data.service';
 import { HALEndpointService } from '../shared/hal-endpoint.service';
-import { createSuccessfulRemoteDataObject$ } from '../../shared/remote-data.utils';
+import {
-import { Observable, of } from 'rxjs';
+  createSuccessfulRemoteDataObject$,
+  createFailedRemoteDataObject$
+} from '../../shared/remote-data.utils';
+import { Observable } from 'rxjs';
 import { RemoteData } from './remote-data';
 import { Root } from './root.model';
-import { RawRestResponse } from '../dspace-rest/raw-rest-response.model';
 import { cold } from 'jasmine-marbles';
 
 describe('RootDataService', () => {
   let service: RootDataService;
   let halService: HALEndpointService;
-  let restService;
+  let requestService;
   let rootEndpoint;
   let findByHrefSpy;
 
@@ -19,10 +21,10 @@ describe('RootDataService', () => {
     halService = jasmine.createSpyObj('halService', {
       getRootHref: rootEndpoint,
     });
-    restService = jasmine.createSpyObj('halService', {
+    requestService = jasmine.createSpyObj('requestService', [
-      get: jasmine.createSpy('get'),
+      'setStaleByHref',
-    });
+    ]);
-    service = new RootDataService(null, null, null, halService, restService);
+    service = new RootDataService(requestService, null, null, halService);
 
     findByHrefSpy = spyOn(service as any, 'findByHref');
     findByHrefSpy.and.returnValue(createSuccessfulRemoteDataObject$({}));
@@ -47,12 +49,8 @@ describe('RootDataService', () => {
     let result$: Observable<boolean>;
 
     it('should return observable of true when root endpoint is available', () => {
-      const mockResponse = {
+      spyOn(service, 'findRoot').and.returnValue(createSuccessfulRemoteDataObject$<Root>({} as any));
-        statusCode: 200,
-        statusText: 'OK'
-      } as RawRestResponse;
 
-      restService.get.and.returnValue(of(mockResponse));
       result$ = service.checkServerAvailability();
 
       expect(result$).toBeObservable(cold('(a|)', {
@@ -61,12 +59,8 @@ describe('RootDataService', () => {
     });
 
     it('should return observable of false when root endpoint is not available', () => {
-      const mockResponse = {
+      spyOn(service, 'findRoot').and.returnValue(createFailedRemoteDataObject$<Root>('500'));
-        statusCode: 500,
-        statusText: 'Internal Server Error'
-      } as RawRestResponse;
 
-      restService.get.and.returnValue(of(mockResponse));
       result$ = service.checkServerAvailability();
 
       expect(result$).toBeObservable(cold('(a|)', {
@@ -75,4 +69,12 @@ describe('RootDataService', () => {
     });
 
   });
+
+  describe(`invalidateRootCache`, () => {
+    it(`should set the cached root request to stale`, () => {
+      service.invalidateRootCache();
+      expect(halService.getRootHref).toHaveBeenCalled();
+      expect(requestService.setStaleByHref).toHaveBeenCalledWith(rootEndpoint);
+    });
+  });
 });

src/app/core/data/root-data.service.ts

@@ -7,12 +7,11 @@ import { HALEndpointService } from '../shared/hal-endpoint.service';
 import { Observable, of as observableOf } from 'rxjs';
 import { RemoteData } from './remote-data';
 import { FollowLinkConfig } from '../../shared/utils/follow-link-config.model';
-import { DspaceRestService } from '../dspace-rest/dspace-rest.service';
-import { RawRestResponse } from '../dspace-rest/raw-rest-response.model';
 import { catchError, map } from 'rxjs/operators';
 import { BaseDataService } from './base/base-data.service';
 import { ObjectCacheService } from '../cache/object-cache.service';
 import { dataService } from './base/data-service.decorator';
+import { getFirstCompletedRemoteData } from '../shared/operators';
 
 /**
  * A service to retrieve the {@link Root} object from the REST API.
@@ -25,7 +24,6 @@ export class RootDataService extends BaseDataService<Root> {
     protected rdbService: RemoteDataBuildService,
     protected objectCache: ObjectCacheService,
     protected halService: HALEndpointService,
-    protected restService: DspaceRestService,
   ) {
     super('', requestService, rdbService, objectCache, halService, 6 * 60 * 60 * 1000);
   }
@@ -34,12 +32,13 @@ export class RootDataService extends BaseDataService<Root> {
    * Check if root endpoint is available
    */
   checkServerAvailability(): Observable<boolean> {
-    return this.restService.get(this.halService.getRootHref()).pipe(
+    return this.findRoot().pipe(
       catchError((err ) => {
         console.error(err);
         return observableOf(false);
       }),
-      map((res: RawRestResponse) => res.statusCode === 200)
+      getFirstCompletedRemoteData(),
+      map((rootRd: RemoteData<Root>) => rootRd.statusCode === 200)
     );
   }
 
@@ -60,6 +59,6 @@ export class RootDataService extends BaseDataService<Root> {
    * Set to sale the root endpoint cache hit
    */
   invalidateRootCache() {
-    this.requestService.setStaleByHrefSubstring(this.halService.getRootHref());
+    this.requestService.setStaleByHref(this.halService.getRootHref());
   }
 }

src/app/core/server-check/server-check.guard.spec.ts

@@ -1,68 +1,88 @@
 import { ServerCheckGuard } from './server-check.guard';
-import { Router } from '@angular/router';
+import { Router, NavigationStart, UrlTree, NavigationEnd, RouterEvent } from '@angular/router';
 
-import { of } from 'rxjs';
+import { of, ReplaySubject } from 'rxjs';
-import { take } from 'rxjs/operators';
-
-import { getPageInternalServerErrorRoute } from '../../app-routing-paths';
 import { RootDataService } from '../data/root-data.service';
+import { TestScheduler } from 'rxjs/testing';
 import SpyObj = jasmine.SpyObj;
 
 describe('ServerCheckGuard', () => {
   let guard: ServerCheckGuard;
-  let router: SpyObj<Router>;
+  let router: Router;
+  let eventSubject: ReplaySubject<RouterEvent>;
   let rootDataServiceStub: SpyObj<RootDataService>;
-
+  let testScheduler: TestScheduler;
-  rootDataServiceStub = jasmine.createSpyObj('RootDataService', {
+  let redirectUrlTree: UrlTree;
-    checkServerAvailability: jasmine.createSpy('checkServerAvailability'),
-    invalidateRootCache: jasmine.createSpy('invalidateRootCache')
-  });
-  router = jasmine.createSpyObj('Router', {
-    navigateByUrl: jasmine.createSpy('navigateByUrl')
-  });
 
   beforeEach(() => {
+    testScheduler = new TestScheduler((actual, expected) => {
+      expect(actual).toEqual(expected);
+    });
+    rootDataServiceStub = jasmine.createSpyObj('RootDataService', {
+      checkServerAvailability: jasmine.createSpy('checkServerAvailability'),
+      invalidateRootCache: jasmine.createSpy('invalidateRootCache'),
+      findRoot: jasmine.createSpy('findRoot')
+    });
+    redirectUrlTree = new UrlTree();
+    eventSubject = new ReplaySubject<RouterEvent>(1);
+    router = {
+      events: eventSubject.asObservable(),
+      navigateByUrl: jasmine.createSpy('navigateByUrl'),
+      parseUrl: jasmine.createSpy('parseUrl').and.returnValue(redirectUrlTree)
+    } as any;
     guard = new ServerCheckGuard(router, rootDataServiceStub);
   });
 
-  afterEach(() => {
-    router.navigateByUrl.calls.reset();
-    rootDataServiceStub.invalidateRootCache.calls.reset();
-  });
-
   it('should be created', () => {
     expect(guard).toBeTruthy();
   });
 
-  describe('when root endpoint has succeeded', () => {
+  describe('when root endpoint request has succeeded', () => {
     beforeEach(() => {
       rootDataServiceStub.checkServerAvailability.and.returnValue(of(true));
     });
 
-    it('should not redirect to error page', () => {
+    it('should return true', () => {
-      guard.canActivateChild({} as any, {} as any).pipe(
+      testScheduler.run(({ expectObservable }) => {
-        take(1)
+        const result$ = guard.canActivateChild({} as any, {} as any);
-      ).subscribe((canActivate: boolean) => {
+        expectObservable(result$).toBe('(a|)', { a: true });
-        expect(canActivate).toEqual(true);
-        expect(rootDataServiceStub.invalidateRootCache).not.toHaveBeenCalled();
-        expect(router.navigateByUrl).not.toHaveBeenCalled();
       });
     });
   });
 
-  describe('when root endpoint has not succeeded', () => {
+  describe('when root endpoint request has not succeeded', () => {
     beforeEach(() => {
       rootDataServiceStub.checkServerAvailability.and.returnValue(of(false));
     });
 
-    it('should redirect to error page', () => {
+    it('should return a UrlTree with the route to the 500 error page', () => {
-      guard.canActivateChild({} as any, {} as any).pipe(
+      testScheduler.run(({ expectObservable }) => {
-        take(1)
+        const result$ = guard.canActivateChild({} as any, {} as any);
-      ).subscribe((canActivate: boolean) => {
+        expectObservable(result$).toBe('(b|)', { b: redirectUrlTree });
-        expect(canActivate).toEqual(false);
-        expect(rootDataServiceStub.invalidateRootCache).toHaveBeenCalled();
-        expect(router.navigateByUrl).toHaveBeenCalledWith(getPageInternalServerErrorRoute());
       });
+      expect(router.parseUrl).toHaveBeenCalledWith('/500');
+    });
+  });
+
+  describe(`listenForRouteChanges`, () => {
+    it(`should invalidate the root cache, when the method is first called`, () => {
+        testScheduler.run(() => {
+          guard.listenForRouteChanges();
+          expect(rootDataServiceStub.invalidateRootCache).toHaveBeenCalledTimes(1);
+        });
+    });
+
+    it(`should invalidate the root cache on every NavigationStart event`, () => {
+        testScheduler.run(() => {
+          guard.listenForRouteChanges();
+          eventSubject.next(new NavigationStart(1,''));
+          eventSubject.next(new NavigationEnd(1,'', ''));
+          eventSubject.next(new NavigationStart(2,''));
+          eventSubject.next(new NavigationEnd(2,'', ''));
+          eventSubject.next(new NavigationStart(3,''));
+        });
+        // once when the method is first called, and then 3 times for NavigationStart events
+        expect(rootDataServiceStub.invalidateRootCache).toHaveBeenCalledTimes(1 + 3);
     });
   });
 });

src/app/core/server-check/server-check.guard.ts

@@ -1,8 +1,15 @@
 import { Injectable } from '@angular/core';
-import { ActivatedRouteSnapshot, CanActivateChild, Router, RouterStateSnapshot } from '@angular/router';
+import {
+  ActivatedRouteSnapshot,
+  CanActivateChild,
+  Router,
+  RouterStateSnapshot,
+  UrlTree,
+  NavigationStart
+} from '@angular/router';
 
 import { Observable } from 'rxjs';
-import { take, tap } from 'rxjs/operators';
+import { take, map, filter } from 'rxjs/operators';
 
 import { RootDataService } from '../data/root-data.service';
 import { getPageInternalServerErrorRoute } from '../../app-routing-paths';
@@ -23,17 +30,36 @@ export class ServerCheckGuard implements CanActivateChild {
    */
   canActivateChild(
     route: ActivatedRouteSnapshot,
-    state: RouterStateSnapshot): Observable<boolean> {
+    state: RouterStateSnapshot
+  ): Observable<boolean | UrlTree> {
 
     return this.rootDataService.checkServerAvailability().pipe(
       take(1),
-      tap((isAvailable: boolean) => {
+      map((isAvailable: boolean) => {
         if (!isAvailable) {
-          this.rootDataService.invalidateRootCache();
+          return this.router.parseUrl(getPageInternalServerErrorRoute());
-          this.router.navigateByUrl(getPageInternalServerErrorRoute());
+        } else {
+          return true;
         }
       })
     );
+  }
 
+  /**
+   * Listen to all router events. Every time a new navigation starts, invalidate the cache
+   * for the root endpoint. That way we retrieve it once per routing operation to ensure the
+   * backend is not down. But if the guard is called multiple times during the same routing
+   * operation, the cached version is used.
+   */
+  listenForRouteChanges(): void {
+    // we'll always be too late for the first NavigationStart event with the router subscribe below,
+    // so this statement is for the very first route operation.
+    this.rootDataService.invalidateRootCache();
+
+    this.router.events.pipe(
+      filter(event => event instanceof NavigationStart),
+    ).subscribe(() => {
+      this.rootDataService.invalidateRootCache();
+    });
   }
 }

src/app/core/shared/hal-endpoint.service.spec.ts

@@ -1,4 +1,3 @@
-import { cold, hot } from 'jasmine-marbles';
 import { getMockRequestService } from '../../shared/mocks/request.service.mock';
 import { RequestService } from '../data/request.service';
 import { HALEndpointService } from './hal-endpoint.service';
@@ -7,12 +6,17 @@ import { combineLatest as observableCombineLatest, of as observableOf } from 'rx
 import { environment } from '../../../environments/environment';
 import { RemoteDataBuildService } from '../cache/builders/remote-data-build.service';
 import { createSuccessfulRemoteDataObject$ } from '../../shared/remote-data.utils';
+import { TestScheduler } from 'rxjs/testing';
+import { RemoteData } from '../data/remote-data';
+import { RequestEntryState } from '../data/request-entry-state.model';
 
 describe('HALEndpointService', () => {
   let service: HALEndpointService;
   let requestService: RequestService;
   let rdbService: RemoteDataBuildService;
   let envConfig;
+  let testScheduler;
+  let remoteDataMocks;
   const endpointMap = {
     test: {
       href: 'https://rest.api/test'
@@ -68,7 +72,30 @@ describe('HALEndpointService', () => {
   };
   const linkPath = 'test';
 
+  const timeStamp = new Date().getTime();
+  const msToLive = 15 * 60 * 1000;
+  const payload = {
+    _links: endpointMaps[one]
+  };
+  const statusCodeSuccess = 200;
+  const statusCodeError = 404;
+  const errorMessage = 'not found';
+  remoteDataMocks = {
+    RequestPending: new RemoteData(undefined, msToLive, timeStamp, RequestEntryState.RequestPending, undefined, undefined, undefined),
+    ResponsePending: new RemoteData(undefined, msToLive, timeStamp, RequestEntryState.ResponsePending, undefined, undefined, undefined),
+    ResponsePendingStale: new RemoteData(undefined, msToLive, timeStamp, RequestEntryState.ResponsePendingStale, undefined, undefined, undefined),
+    Success: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.Success, undefined, payload, statusCodeSuccess),
+    SuccessStale: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.SuccessStale, undefined, payload, statusCodeSuccess),
+    Error: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.Error, errorMessage, undefined, statusCodeError),
+    ErrorStale: new RemoteData(timeStamp, msToLive, timeStamp, RequestEntryState.ErrorStale, errorMessage, undefined, statusCodeError),
+  };
+
   beforeEach(() => {
+    testScheduler = new TestScheduler((actual, expected) => {
+      // asserting the two objects are equal
+      // e.g. using chai.
+      expect(actual).toEqual(expected);
+    });
     requestService = getMockRequestService();
     rdbService = jasmine.createSpyObj('rdbService', {
       buildFromHref: createSuccessfulRemoteDataObject$({
@@ -111,20 +138,28 @@ describe('HALEndpointService', () => {
     });
 
     it(`should return the endpoint URL for the service's linkPath`, () => {
-      spyOn(service as any, 'getEndpointAt').and
+      testScheduler.run(({ cold, expectObservable }) => {
-        .returnValue(hot('a-', { a: 'https://rest.api/test' }));
+        spyOn(service as any, 'getEndpointAt').and
-      const result = service.getEndpoint(linkPath);
+          .returnValue(cold('a-', { a: 'https://rest.api/test' }));
+        const result = service.getEndpoint(linkPath);
 
-      const expected = cold('(b|)', { b: endpointMap.test.href });
+        const expected = '(b|)';
-      expect(result).toBeObservable(expected);
+        const values = {
+          b: endpointMap.test.href
+        };
+        expectObservable(result).toBe(expected, values);
+      });
     });
 
     it('should return undefined for a linkPath that isn\'t in the endpoint map', () => {
-      spyOn(service as any, 'getEndpointAt').and
+      testScheduler.run(({ cold, expectObservable }) => {
-        .returnValue(hot('a-', { a: undefined }));
+        spyOn(service as any, 'getEndpointAt').and
-      const result = service.getEndpoint('unknown');
+          .returnValue(cold('a-', { a: undefined }));
-      const expected = cold('(b|)', { b: undefined });
+        const result = service.getEndpoint('unknown');
-      expect(result).toBeObservable(expected);
+        const expected = '(b|)';
+        const values = { b: undefined };
+        expectObservable(result).toBe(expected, values);
+      });
     });
   });
 
@@ -183,29 +218,118 @@ describe('HALEndpointService', () => {
     });
 
     it('should return undefined as long as getRootEndpointMap hasn\'t fired', () => {
-      spyOn(service as any, 'getRootEndpointMap').and
+      testScheduler.run(({ cold, expectObservable }) => {
-        .returnValue(hot('----'));
+        spyOn(service as any, 'getRootEndpointMap').and
+          .returnValue(cold('----'));
 
-      const result = service.isEnabledOnRestApi(linkPath);
+        const result = service.isEnabledOnRestApi(linkPath);
-      const expected = cold('b---', { b: undefined });
+        const expected = 'b---';
-      expect(result).toBeObservable(expected);
+        const values = { b: undefined };
+        expectObservable(result).toBe(expected, values);
+      });
     });
 
     it('should return true if the service\'s linkPath is in the endpoint map', () => {
-      spyOn(service as any, 'getRootEndpointMap').and
+      testScheduler.run(({ cold, expectObservable }) => {
-        .returnValue(hot('--a-', { a: endpointMap }));
+        spyOn(service as any, 'getRootEndpointMap').and
-      const result = service.isEnabledOnRestApi(linkPath);
+          .returnValue(cold('--a-', { a: endpointMap }));
-      const expected = cold('b-c-', { b: undefined, c: true });
+        const result = service.isEnabledOnRestApi(linkPath);
-      expect(result).toBeObservable(expected);
+        const expected = 'b-c-';
+        const values = { b: undefined, c: true };
+        expectObservable(result).toBe(expected, values);
+      });
     });
 
     it('should return false if the service\'s linkPath isn\'t in the endpoint map', () => {
-      spyOn(service as any, 'getRootEndpointMap').and
+      testScheduler.run(({ cold, expectObservable }) => {
-        .returnValue(hot('--a-', { a: endpointMap }));
+        spyOn(service as any, 'getRootEndpointMap').and
+          .returnValue(cold('--a-',  { a: endpointMap }));
 
-      const result = service.isEnabledOnRestApi('unknown');
+        const result = service.isEnabledOnRestApi('unknown');
-      const expected = cold('b-c-', { b: undefined, c: false });
+        const expected = 'b-c-';
-      expect(result).toBeObservable(expected);
+        const values = { b: undefined, c: false };
+        expectObservable(result).toBe(expected, values);
+      });
+    });
+
+  });
+
+  describe(`getEndpointMapAt`, () => {
+    const href = 'https://rest.api/some/sub/path';
+
+    it(`should call requestService.send with a new EndpointMapRequest for the given href. useCachedVersionIfAvailable should be true`, () => {
+      testScheduler.run(() => {
+        (service as any).getEndpointMapAt(href);
+      });
+      const expected = new EndpointMapRequest(requestService.generateRequestId(), href);
+      expect(requestService.send).toHaveBeenCalledWith(expected, true);
+    });
+
+    it(`should call rdbService.buildFromHref with the given href`, () => {
+      testScheduler.run(() => {
+        (service as any).getEndpointMapAt(href);
+      });
+      expect(rdbService.buildFromHref).toHaveBeenCalledWith(href);
+    });
+
+    describe(`when the RemoteData returned from rdbService is stale`, () => {
+      it(`should re-request it`, () => {
+        spyOn(service as any, 'getEndpointMapAt').and.callThrough();
+          testScheduler.run(({ cold }) => {
+            (rdbService.buildFromHref as jasmine.Spy).and.returnValue(cold('a', { a: remoteDataMocks.ResponsePendingStale }));
+            // we need to subscribe to the result, to ensure the "tap" that does the re-request can fire
+            (service as any).getEndpointMapAt(href).subscribe();
+          });
+          expect((service as any).getEndpointMapAt).toHaveBeenCalledTimes(2);
+      });
+    });
+
+    describe(`when the RemoteData returned from rdbService isn't stale`, () => {
+      it(`should not re-request it`, () => {
+        spyOn(service as any, 'getEndpointMapAt').and.callThrough();
+          testScheduler.run(({ cold }) => {
+            (rdbService.buildFromHref as jasmine.Spy).and.returnValue(cold('a', { a: remoteDataMocks.ResponsePending }));
+            // we need to subscribe to the result, to ensure the "tap" that does the re-request can fire
+            (service as any).getEndpointMapAt(href).subscribe();
+          });
+          expect((service as any).getEndpointMapAt).toHaveBeenCalledTimes(1);
+      });
+    });
+
+    it(`should emit exactly once, returning the endpoint map in the response, when the RemoteData completes`, () => {
+      testScheduler.run(({ cold, expectObservable }) => {
+        (rdbService.buildFromHref as jasmine.Spy).and.returnValue(cold('a-b-c-d-e-f-g-h-i-j-k-l', {
+          a: remoteDataMocks.RequestPending,
+          b: remoteDataMocks.ResponsePending,
+          c: remoteDataMocks.ResponsePendingStale,
+          d: remoteDataMocks.SuccessStale,
+          e: remoteDataMocks.RequestPending,
+          f: remoteDataMocks.ResponsePending,
+          g: remoteDataMocks.Success,
+          h: remoteDataMocks.SuccessStale,
+          i: remoteDataMocks.RequestPending,
+          k: remoteDataMocks.ResponsePending,
+          l: remoteDataMocks.Error,
+        }));
+        const expected = '------------(g|)';
+        const values = {
+          g: endpointMaps[one]
+        };
+        expectObservable((service as any).getEndpointMapAt(one)).toBe(expected, values);
+      });
+    });
+
+    it(`should emit undefined when the response doesn't have a payload`, () => {
+      testScheduler.run(({ cold, expectObservable }) => {
+        (rdbService.buildFromHref as jasmine.Spy).and.returnValue(cold('a', {
+          a: remoteDataMocks.Error,
+        }));
+        const expected = '(a|)';
+        const values = {
+          g: undefined
+        };
+        expectObservable((service as any).getEndpointMapAt(href)).toBe(expected, values);
+      });
     });
 
   });

src/app/core/shared/hal-endpoint.service.ts

@@ -1,5 +1,12 @@
 import { Observable } from 'rxjs';
-import { distinctUntilChanged, map, startWith, switchMap, take } from 'rxjs/operators';
+import {
+  distinctUntilChanged,
+  map,
+  startWith,
+  switchMap,
+  take,
+  tap, filter
+} from 'rxjs/operators';
 import { RequestService } from '../data/request.service';
 import { EndpointMapRequest } from '../data/request.models';
 import { hasValue, isEmpty, isNotEmpty } from '../../shared/empty.util';
@@ -9,7 +16,7 @@ import { EndpointMap } from '../cache/response.models';
 import { getFirstCompletedRemoteData } from './operators';
 import { RemoteDataBuildService } from '../cache/builders/remote-data-build.service';
 import { RemoteData } from '../data/remote-data';
-import { UnCacheableObject } from './uncacheable-object.model';
+import { CacheableObject } from '../cache/cacheable-object.model';
 
 @Injectable()
 export class HALEndpointService {
@@ -33,9 +40,18 @@ export class HALEndpointService {
 
     this.requestService.send(request, true);
 
-    return this.rdbService.buildFromHref<UnCacheableObject>(href).pipe(
+    return this.rdbService.buildFromHref<CacheableObject>(href).pipe(
+      // Re-request stale responses
+      tap((rd: RemoteData<CacheableObject>) => {
+        if (hasValue(rd) && rd.isStale) {
+          this.getEndpointMapAt(href);
+        }
+      }),
+      // Filter out all stale responses. We're only interested in a single, non-stale,
+      // completed RemoteData
+      filter((rd: RemoteData<CacheableObject>) => !rd.isStale),
       getFirstCompletedRemoteData(),
-      map((response: RemoteData<UnCacheableObject>) => {
+      map((response: RemoteData<CacheableObject>) => {
         if (hasValue(response.payload)) {
           return response.payload._links;
         } else {

src/modules/app/browser-init.service.ts

@@ -32,6 +32,7 @@ import { logStartupMessage } from '../../../startup-message';
 import { MenuService } from '../../app/shared/menu/menu.service';
 import { RootDataService } from '../../app/core/data/root-data.service';
 import { firstValueFrom, Subscription } from 'rxjs';
+import { ServerCheckGuard } from '../../app/core/server-check/server-check.guard';
 
 /**
  * Performs client-side initialization.
@@ -56,7 +57,8 @@ export class BrowserInitService extends InitService {
     protected authService: AuthService,
     protected themeService: ThemeService,
     protected menuService: MenuService,
-    private rootDataService: RootDataService
+    private rootDataService: RootDataService,
+    protected serverCheckGuard: ServerCheckGuard,
   ) {
     super(
       store,
@@ -172,4 +174,13 @@ export class BrowserInitService extends InitService {
       });
   }
 
+  /**
+   * Start route-listening subscriptions
+   * @protected
+   */
+  protected initRouteListeners(): void {
+    super.initRouteListeners();
+    this.serverCheckGuard.listenForRouteChanges();
+  }
+
 }