OfferingsManager: don't clear offerings cache timestamp when reques…

…t fails (#2359)

There is no reason to clear this and make the cache immediately stale.
Instead, failed requests would eventually make the cache stale after a
certain duration.

Sources/Purchasing/OfferingsManager.swift

@@ -241,7 +241,6 @@ private extension OfferingsManager {
     ) {
         Logger.appleError(Strings.offering.fetching_offerings_error(error: error,
                                                                     underlyingError: error.underlyingError))
-        self.deviceCache.clearOfferingsCacheTimestamp()
         self.dispatchCompletionOnMainThreadIfPossible(completion, value: .failure(error))
     }
 

Tests/UnitTests/Purchasing/OfferingsManagerTests.swift

@@ -336,27 +336,6 @@ extension OfferingsManagerTests {
         }
     }
 
-    func testFailBackendDeviceCacheClearsOfferingsCache() {
-        // given
-        self.mockOfferings.stubbedGetOfferingsCompletionResult = .failure(MockData.unexpectedBackendResponseError)
-        self.mockOfferingsFactory.emptyOfferings = true
-        self.mockSystemInfo.stubbedIsApplicationBackgrounded = false
-
-        let expectedCallCount = 1
-
-        // when
-        waitUntil { completed in
-            self.offeringsManager.offerings(appUserID: MockData.anyAppUserID) { _ in
-                completed()
-            }
-        }
-
-        // then
-        expect(self.mockOfferings.invokedGetOfferingsForAppUserIDCount) == expectedCallCount
-        expect(self.mockDeviceCache.clearOfferingsCacheTimestampCount) == expectedCallCount
-        expect(self.mockOfferings.invokedGetOfferingsForAppUserIDParameters?.randomDelay) == false
-    }
-
     func testUpdateOfferingsCacheOK() throws {
         // given
         self.mockOfferings.stubbedGetOfferingsCompletionResult = .success(MockData.anyBackendOfferingsResponse)