overlord/devicestate: fix do-install-setup-storage-encryption check for preinstall context availability (canonical#16584)

* overlord/devicestate: fix do-install-setup-storage-encryption check for preinstall context availability

* fixup! overlord/devicestate: fix do-install-setup-storage-encryption check for preinstall context availability

Author: ernestl

overlord/devicestate/devicestate_systems_test.go

@@ -3037,12 +3037,18 @@ func mockHelperForEncryptionAvailabilityCheck(s suiteWithAddCleanup, c *C, isSup
 		}
 	}
 
-	if isSupportedUbuntuHybrid && cacheLabel != "" {
+	if cacheLabel != "" {
 		// populate the cache with encryption support information that
-		// includes a check context similar to having performed an
-		// initial preinstall check
+		// mimics what would happen when a preinstall check takes place
+		// as per usual installer flow
 		encInfo := &install.EncryptionSupportInfo{}
-		encInfo.SetAvailabilityCheckContext(&secboot.PreinstallCheckContext{})
+		if isSupportedUbuntuHybrid {
+			// hybrid installation flow populates the preinstall check context
+			encInfo.SetAvailabilityCheckContext(&secboot.PreinstallCheckContext{})
+		}
+		// non-hydrid install flow uses the simple availability check that does not produce
+		// a preinstall check context
+
 		s.DeviceManager().SetEncryptionSupportInfoInCacheUnlocked(cacheLabel, encInfo)
 	}
 

overlord/devicestate/handlers_install.go

@@ -1371,7 +1371,9 @@ func (m *DeviceManager) doInstallSetupStorageEncryption(t *state.Task, _ *tomb.T
 	}
 
 	var checkAction *secboot.PreinstallAction
-	if m.readCacheEncryptionSupportInfoLocked(systemLabel) != nil {
+	cachedEncInfo := m.readCacheEncryptionSupportInfoLocked(systemLabel)
+
+	if cachedEncInfo != nil && cachedEncInfo.CheckContext() != nil {
 		// If a cached context is available, the preinstall check was previously run
 		// and must be repeated. Set an action to signal reuse of the preinstall check
 		// context. Use the inert "ActionNone" to repeat the check without requesting