fix(offline): order connectivity probe observations

Author: rdlabo

projects/kit/offline/src/lib/offline-network-verification.spec.ts

@@ -59,20 +59,30 @@ describe('OfflineNetworkService connection verification', () => {
     expect(service.checkingConnection()).toBe(false);
   });
 
-  it('leaves a newer successful observation intact after a status-zero failure and permits retry', async () => {
+  it('records a status-zero failure when no newer API observation exists and permits retry', async () => {
     const markApiFailure = vi.spyOn(service, 'markApiFailure');
     const first = service.verifyConnection('/status');
-    service.markApiSuccess();
     http.expectOne('/status').error(new ProgressEvent('error'));
     await expect(first).resolves.toBe(false);
-    expect(markApiFailure).not.toHaveBeenCalled();
-    expect(service.state()).toBe('unverified');
+    expect(markApiFailure).toHaveBeenCalledOnce();
+    expect(service.state()).toBe('offline');
 
     const second = service.verifyConnection('/status');
     http.expectOne('/status').flush({});
     await expect(second).resolves.toBe(true);
   });
 
+  it('does not let an older probe failure overwrite a newer successful API observation', async () => {
+    const markApiFailure = vi.spyOn(service, 'markApiFailure');
+    const verification = service.verifyConnection('/status');
+    service.markApiSuccess();
+    http.expectOne('/status').error(new ProgressEvent('error'));
+
+    await expect(verification).resolves.toBe(false);
+    expect(markApiFailure).not.toHaveBeenCalled();
+    expect(service.state()).toBe('unverified');
+  });
+
   it('does not overwrite reachability when a stalled check times out and permits retry', async () => {
     vi.useFakeTimers();
     const markApiFailure = vi.spyOn(service, 'markApiFailure');

projects/kit/offline/src/lib/offline-network.service.ts

@@ -22,6 +22,7 @@ export class OfflineNetworkService {
   readonly #apiReachable = signal<boolean | null>(null);
   readonly #appActive = signal(true);
   readonly #lifecycleRevision = signal(0);
+  #apiReachabilityRevision = 0;
   #networkRevision = 0;
   readonly #listeners: PluginListenerHandle[] = [];
   #initialized = false;
@@ -67,10 +68,12 @@ export class OfflineNetworkService {
   }
 
   markApiSuccess(): void {
+    this.#apiReachabilityRevision += 1;
     this.#apiReachable.set(true);
   }
 
   markApiFailure(): void {
+    this.#apiReachabilityRevision += 1;
     this.#apiReachable.set(false);
   }
 
@@ -81,6 +84,7 @@ export class OfflineNetworkService {
   verifyConnection(url: string, timeoutMs = DEFAULT_OFFLINE_CONNECTION_VERIFICATION_TIMEOUT_MS): Promise<boolean> {
     if (this.#connectionVerification) return this.#connectionVerification;
 
+    const startingApiReachabilityRevision = this.#apiReachabilityRevision;
     this.#checkingConnection.set(true);
     const verification = firstValueFrom(
       this.#http
@@ -94,7 +98,12 @@ export class OfflineNetworkService {
             this.markApiSuccess();
             return true;
           }),
-          catchError(() => of(false)),
+          catchError((error: unknown) => {
+            if (isOfflineFallbackError(error) && this.#apiReachabilityRevision === startingApiReachabilityRevision) {
+              this.markApiFailure();
+            }
+            return of(false);
+          }),
         ),
     ).finally(() => {
       this.#checkingConnection.set(false);

projects/kit/offline/src/lib/offline-request-policy.ts

@@ -5,7 +5,7 @@ import { HttpContextToken } from '@angular/common/http';
 
 /** outbox再送時にoffline interceptorだけを迂回する。認証・retryは維持する。 */
 export const OFFLINE_BYPASS = new HttpContextToken<boolean>(() => false);
-/** Keeps a manual reachability probe from overwriting a newer successful API observation. */
+/** Lets a manual reachability probe apply its transport failure with its own observation-order guard. */
 export const OFFLINE_IGNORE_TRANSPORT_FAILURE = new HttpContextToken<boolean>(() => false);
 /** Header attached to synthetic local or optimistic responses. */
 export const OFFLINE_RESPONSE_HEADER = 'X-Offline-Response';